Races of brewer's yeast. Atlas of industrial alcohol yeast Saccharomyces cerevisiae race XII (for employees of distilleries processing grain)
Races of brewer's yeast
In brewing, bottom-fermenting yeast is used, adapted to relatively low temperatures. Brewer's yeast must be microbiologically pure, and also have the ability to form flocculation, quickly settle to the bottom of the fermenter and give a transparent drink with a certain taste and aroma. Highly fermenting and easily flaking yeasts include Froberg bottom-fermenting brewer's yeast (Saccharomyces cerevisiae Froberg), yeast races V and 776.
In breweries, yeast of the 776 race, which was bred at the beginning of the 20th century, was widely used. This yeast is considered particularly suitable for fermenting wort prepared with the addition of unmalted materials or from malted barley with a low degree of germination. Yeast of race 776 is medium-fermenting, during the period of main fermentation on wort with a concentration of 11%, they form approximately 2.7% CO 2 . Cells are ovoid, 8-10 µm long and 5-6 µm wide. Yeast mass gain 1: 5.4. The lightening ability is satisfactory.
Of the other yeasts, breweries use races 11, 41, 44, S-Lvovskaya, and others, which differ in fermentation energy, precipitation ability, and growth energy.
Race 11 yeast is highly fermentative, with good clarification capability. Beer made with race 11 yeast tastes good. This race is widely used in breweries.
Yeast of race 41 is medium fermenting, with good sedimentation ability. When the wort is fermented with race 41, a mild beer with a clean taste is obtained.
Race 44 yeast is medium fermenting. Sedimentation ability is good. They give beer fullness of taste and give good results when used in the production of water with increased hardness.
Race S yeast is medium fermenting. Sedimentation ability is good. Give beer with a mild clean taste.
Race P yeast is medium-fermenting, well clarifies beer and determines a pleasant clean taste.
Race F yeast is characterized by a good clarification ability and imparts a pleasant aroma to the beer. The race is resistant to the action of foreign microorganisms.
Yeast of race A (isolated at the Riga brewery "Aldaris") ferments the wort in 7-8 days, clarifies beer well and is resistant to infection.
A number of strongly fermenting yeast strains (28, 48, 102) were obtained by different selection methods at the All-Russian Research Institute of the Beer and Non-Alcohol Industry (28, 48, 102), which have a significantly higher fermentative energy than the yeast of the original race 11.
Top-fermented brewer's yeast is widely used in England in the preparation of Porter. They are also used to make Berlin lager beer and other drinks. For the preparation of Velvet beer, strain 191 K is used, which intensively ferments monosaccharides and maltose, but does not ferment sucrose, raffinose and lactose.
^ Wine yeast races
In winemaking, yeasts are valued, which multiply rapidly, have the ability to suppress other types of yeast and microorganisms and give the wine an appropriate bouquet. The yeast used in winemaking belongs to a peculiar species of Saccharomyces ellipsoideus. Their cells are oblong-oval in shape. Yeast vigorously ferments glucose, fructose, sucrose and maltose. In different localities and from different young wines, several distinct varieties or races of this species have been isolated. In winemaking, almost all production cultures of yeast are of their own, local origin. These include races Magarach 7, Massandra 3, Pino 14, Kakhuri and many others. Along with these races, some foreign ones are also used, for example, the Steinberg race, isolated in Germany in 1892 and 1893, and the Champagne-Ai race.
Most wine yeast is a bottom-fermenting yeast.
For the preparation of white table wines, the races Pinot 14, Feodosia 1/19, Aligote, Riesling Anapsky are used.
Race Pinot 14 has egg-shaped cells, well ferments grape must with a sugar content of 20% with the formation of 11.57% alcohol; the optimum temperature for development and fermentation is 18: -25°C. This race is cold and acid resistant; the optimal pH value is 2.9-3.9.
Race Theodosius 1/19 - large-celled, pulverized, very energetic, quickly ferments grape must and ferments it well; has a wide temperature range of fermentation (from 9 to 35°C) and can be used as cold-resistant and heat-resistant.
There are several races of Aligote yeast, and they are all strong, with high fermentation energy. Riesling Anapsky yeast also belongs to vigorous fermenters.
For the preparation of strong wines, the Massandra 3 race is used with an ovoid cell shape, pulverized; the optimal pH value is 3.7-4.05; the optimum fermentation temperature is 18-20°C. Grape must with a sugar content of 20% is completely fermented; when fermenting concentrated grape must (30% sugar), it forms 11.8% alcohol by volume and leaves 8.7% sugar unfermented.
Race Magarach 125, named to commemorate the 125th anniversary of the first planting of grapes at the Magarach Institute, is used to produce strong and dessert wines. This race well ferments highly concentrated grape must with a sugar content of 27-30%, cold-resistant.
Race Kakhuri 2 is widely used for the preparation of champagne wine materials and wines. It ferments grape must with a sugar content of 20% with the formation of 11.4% alcohol, 0.28% sugar remains unfermented. This race is quite cold-resistant (at a temperature of 14-15 ° C, the must ferments on the 2nd day) and ferments well; the optimal pH value is 3.4-3.6.
Race Champagne 7, used for champagnization of wine in bottles, is isolated from race Kakhuri 5 and is characterized by the formation of a sediment that is difficult to stir up; intensively ferments at a temperature of 4-9°C, although the wort ferments only on the 5-6th day.
Of the wine yeasts, the Leningradskaya race is considered the most cold-resistant, and the Ashgabat 3 race is considered the most heat-resistant.
In the production of sherry, special strains of yeast are used, which are a variety of the Saccharomyces oviformis species. Sherry yeast forms a film on the surface of wine in incomplete barrels, thanks to the development of which the wine acquires a special bouquet and taste.
Through careful selection of the most important production characteristics, several races of sherry yeasts (13, 15 and 20) with high film-forming ability have been identified. Later, from the production that used the Sherry 20 race, a more effective Sherry 20-C race was selected, which was widely used in many sherry factories.
In fruit and berry winemaking, selected races of yeast isolated from various fruit and berry juices are used. Fruit and berry juices are rich in yeast, which have all the qualities necessary for production and are biologically adapted to the conditions of development in the original fruit and berry juices. Therefore, yeast strains isolated from strawberry juices are used to ferment strawberry juices, and yeast strains isolated from cherry juices are used to ferment cherry juices, etc.
The following strains have become widespread in fruit and berry winemaking: apple 46, 58, cranberry 17, currant 16, lingonberry 3, 7, 10, raspberry 7/5, 25, 28, 28/10, cherry 3, 6, strawberry 7 , 4, 9.
The named strains of yeast provide a normal course of fermentation, completeness of fermentation, fast clarification and good taste of wine; they ferment glucose, fructose, sucrose, maltose, galactose and do not ferment lactose and mannitol.
Yeast races Moscow 30, Apple 7, Cherry 33, Chernomorodinovaya 7, Raspberry 10 and Plum 21 are successfully used in fruit and berry winemaking. Pure yeast culture Moscow 30 is recommended for fermentation of cranberry must; Apple 7 and Cherry 33 - for fermenting apple must; Blackcurrant 7 and Cherry 33 - for the fermentation of blackcurrant and cherry must.
^
4 Chemistry of alcoholic fermentation. Secondary and by-products of alcoholic fermentation
Alcoholic fermentation is a chain of enzymatic processes, the end result of which is the breakdown of hexose with the formation of alcohol and CO 2 and the delivery to the yeast cell of the energy that is necessary for the formation of new substances used for life processes, including growth and reproduction. By chemical nature, alcoholic fermentation is a catalytic process that occurs under the action of biological catalysts - enzymes.
The modern theory of alcoholic fermentation is the result of the work of many scientists from around the world.
For elucidation of the processes of fermentation, the works of outstanding Russian scientists were of great importance: Lebedev, Kostychev, Favorsky, Ivanov, Engelhardt.
According to modern concepts, alcoholic fermentation is a complex continuous process of sugar breakdown, catalyzed by various enzymes with the formation of 12 intermediate products.
1 The initial stage of glucose conversion is its phosphorylation reaction with the participation of the enzyme glucosinase. A phosphate residue from the ATP molecule, which is located in yeast cells, is attached to the glucose molecule, and glucose-6-phosphate is formed, and ATP is converted to ADP:
C 6 H 12 O 6 + ATP → CH 2 O (H 2 PO 3) (CHOH) 4 CHO + ADP
Glucose Glucose-6-phosphate
As a result of the addition of a phosphate residue from the ATP molecule to glucose, the reactivity of the latter increases.
2 Glucose-6-phosphate, by isomerization under the action of the enzyme glucose phosphate isomerase, turns reversibly into the form of fructose:
CH 2 O (H 2 RO 3) (CHOH) 4 CHO → CH 2 O (H 2 RO 3) (CHOH) 3 COCH 2 OH
Glucose-6-phosphate Fructose-6-phosphate
3 Further, under the action of the enzyme phosphofructokinase, another phosphorus residue is transferred from the second ATP molecule to fructose-6-phosphate and fructose-1,6-diphosphate and a new ADP molecule are formed:
CH 2 O (H 2 RO 3) (CHOH) 3 COCH 2 OH + ATP →
Fructose 6-phosphate
→ CH 2 O (H 2 RO 3) (CHOH) 3 COCH 2 O (H 2 RO) + ADP
Fructose 1,6-diphosphate
Ethers of glucose-6-phosphate and fructose-6-phosphate form an equilibrium mixture, called the Emden ester and consisting of 70-75% Robison ester (glucose) and 25% Neuberg ester (fructose).
The formation of fructose-1,6-diphosphate ends the preparatory the stage of alcoholic fermentation with the transfer of high-energy phosphate bonds and with the transformation of hexose into a labile oxyform, which is easily subjected to further enzymatic transformations.
4 The next most important step is desmolysis - breaking the carbon chain of fructose diphosphate with the formation of two
phosphotriosis molecules. The symmetrical arrangement of phosphoric acid residues at the ends of the fructose molecule makes it easier to break its carbon chain right in the middle. Fructose diphosphate decomposes into two trioses: phosphoglyceraldehyde and phosphodioxyacetone. The reaction is catalyzed by the enzyme aldolase and is reversible:
CH 2 O (H 2 RO 3) (CHOH) 3 COCH 2 O (H 2 RO) → CH 2 O (H 2 P0 3) COCH 2 OH +
Fructose 1,6-diphosphate Phosphodioxyacetone
CH 2 0 (H 2 ROz) SUPERB (4)
3-phosphoglyceraldehyde
The main role in further transformations during alcoholic fermentation belongs to 3-phosphoglyceraldehyde, but it is found in the fermented liquid only in a small amount. This is due to the mutual transition of the ketose to aldose isomer and back under the action of the enzyme triose phosphate isomerase (5.3.1.1)
CH 2 0 (H 2 P0 3) COCH 2 OH; £ CH 2 0 (H 2 P0 3) SWEET
Phosphodioxyacetone 3-Phosphoglyceraldehyde
As the phosphoglycerol aldehyde is further converted, new amounts of it are formed during the isomerization of phosphodioxyacetone.
5. The next step is the oxidation of two molecules of 3^phosphoglyceraldehyde. This reaction is catalyzed by triose phosphate dehydrogenase (1.2.1.12), whose coenzyme is NAD (nicotinamide adenine dinucleotide). The phosphoric acid of the medium is involved in the oxidation. The reaction proceeds according to the following equation: 2CH 2 0 (H 2 P0 3) SHORTLY + 2H 3 P0 4 + 2NAD Triose phosphate dehydrogenase ->
3-phosphoglyceraldehyde
->- 2CH 2 0 (H 2 P0 3) CHONCOO w (H 2 P0 3) + 2NAD H 2 (5)
1,3-diphosphoglyceric acid
The 3-phosphoglyceraldehyde molecule adds phosphate, and the hydrogen is transferred to the NAD coenzyme, which is reduced. The energy released as a result of the oxidation of 3-phosphoglyceraldehyde is accumulated in the macroergic bond of the resulting 1,3-diphosphoglycerol
Acids.
6. Next, the phosphate residue of 1,3-diphosphoglyceric acid
you, containing a macroergic bond, with the participation of an enzyme
phosphoglycerate kinase (2.7.2.3) is transferred to an ADP molecule.
3-phosphoglyceric acid is formed, and ADP, acquiring
additional macroergic bond, turns into ATP:
2CH 2 0 (H 2 P0 3) CHOHCOOH co (H 2 P0 3) + 2ADP-> 2CH 2 0 (H 2 P0 3) CHOHCOOH +
1,3-diphosphoglyceric acid 3-phosphoglyceric acid
7. Then, under the action of the enzyme phosphoglyceromutase
(2.7.5.3) the phosphoric acid residue moves from the third
carbon to the second, and as a result, 3-phosphoglyceric acid
lota is converted to 2-phosphoglyceric acid:
2CH 2 (H 2 P0 3) CHOHCOOH ^t 2CH 2 0HCH0 (H 2 P0 3) COOH. (7)
3-phosphoglyceric acid 2-phosphoglyceric acid
8. The next step is the dephosphorylation of 2-phospho-
foglyceric acid. At the same time, 2-phosphoglyceric acid
lot under the action of the enzyme enolase (4.2.1.11) by dehydration
tiation (loss of water) is converted into phosphoenolpyrovino-
gradic acid:
2CH 2 OHCHO (H 2 P0 3) COOH qt 2CH 3: CO co (H 2 P0 3) COOH + 2H 2 0. (8)
2-phosphoglyceric acid Sosphoenolpyruvic acid
During this transformation, the redistribution of intramolecular energy occurs and most of it is accumulated in the macroergic phosphate bond.
9. Very unstable phosphoenolpyruvic acid
easily dephosphorylated, while the phosphoric acid residue
by the action of the enzyme pyruvate kinase (2.7.1.40)
together with a macroergic bond to the ADP molecule. As a result
a more stable keto form of pyruvic acid is formed
you, and ADP is converted to ATP:
2CH 2: CO syu (H 2 P0 3) COOH + 2ADP - * 2CH 3 ^ COCOOH + 2ATP. (3)
Phosphoenol pyruvic pyruvic
acid acid
10. Pyruvic acid under the action of the enzyme pi-
ruvate decarboxylase (4.1.1.1) is decarboxylated with cleavage
nii CO 2 and the formation of acetaldehyde:
2CH 3 ^ COCOOH - * 2C0 2 + 2CH 3 CHO. (10)
pyruvic aldehyde
11. Acetic aldehyde with the participation of the enzyme alcohol dehy-
rogenase (1.1.1.1) interacts with NAD-H 2 formed
earlier, during the oxidation of phosphoglyceraldehyde to phospho-
glyceric acid [see equation (5)]. As a result, vinegar
aldehyde is reduced to ethyl alcohol, and the coenzyme
NAD-H 2 is regenerated again (oxidized to NAD):
2SN 3 CHO + 2NAD H 2 Z 2CH 3 CH 2 OH + 2OVER. (eleven)
So, the final stage of fermentation is the reduction reaction of acetaldehyde to ethyl alcohol.
From the considered cycle of alcoholic fermentation reactions, it can be seen that 2 alcohol molecules and 2 CO 2 molecules are formed from each glucose molecule.
In the process of alcoholic fermentation, four ATP molecules are formed [see. equations (6) and (9)], but two of them are spent on phosphorylation of hexoses [see. equations (1) and (3)]. Thus, only 2 g-mol of ATP is stored.
It was previously indicated that 41.9 kJ is spent on the formation of each gram-molecule of ATP from ADP, and 83.8 kJ, respectively, goes into the energy of two ATP molecules. Therefore, during the fermentation of 1 g-mol of glucose, the yeast receives an energy of about 84 kJ. This is the biological meaning of fermentation. With the complete breakdown of glucose into CO 2 and water, 2874 kJ is released, and when 1 g-mol of glucose is oxidized to CO 2 and H 2 0 during aerobic respiration, 2508 kJ is accumulated, since the resulting ethanol still retains its potential energy. Thus, from an energy point of view, fermentation is an uneconomical process.
The fermentation of individual sugars occurs in a certain sequence, determined by the rate of their diffusion into the yeast cell. Glucose and fructose are the fastest fermented by yeast. However, sucrose as such disappears into the must (is inverted) at the beginning of fermentation. It is hydrolyzed by p-fructofuranosidase (3.2.1.26) of the yeast cell membrane to form hexoses (glucose and fructose), which are easily used by the cell. When there is almost no fructose and glucose left in the wort, the yeast begins to consume maltose.
§ 5. SECONDARY AND BY-PRODUCTS OF ALCOHOLIC FERMENTATION
All substances resulting from the fermentation of sugar by yeast, with the exception of alcohol and CO 2, are secondary products of alcoholic fermentation. In addition to them, there are by-products of alcoholic fermentation, which are formed not from sugar, but from other substances in the fermented substrate. These include amyl, isoamyl, iso-butyl and other alcohols known as fusel oil.
Of the secondary products of alcoholic fermentation, glycerin, acetic aldehyde, pyruvic, acetic, succinic, citric and lactic acids, acetoin (acetylmethyl-carbinol), 2,3-butylene glycol and diacetyl are known. Under aerobic conditions, pyruvic acid is also the starting material for the tricarboxylic acid cycle (Krebs cycle), according to which acetic, citric, malic, and succinic acids are formed from it. Higher alcohols are also formed from pyruvic acid by amination to alanine, which in turn is transaminated into the corresponding keto acid. Under the conditions of alcoholic fermentation, keto acids, being reduced, form higher alcohols. Therefore, secondary and by-products of alcoholic fermentation cannot be strictly distinguished.
Acetic aldehyde can experience dismutation with the formation of acetic acid and ethyl alcohol (Cannizzaro reaction):
CH 3 CH + CH 3 CH + H 2 0 \u003d CH3COOH + CH 3 CH 2 OH.
One of the aldehyde molecules is oxidized to an acid, while the other is reduced to an alcohol. In an alkaline environment, one molecule
Acetic aldehyde enters into a redox reaction with the second molecule of acetaldehyde; in this case, ethyl alcohol, acetic acid and, at the same time, glycerin are formed, which is expressed by the following total equation:
2C 6 Hi 2 0 6 + H 2 0 \u003d 2CH 2 OHCHNOCH 2 OH + CH 3 CH 2 OH + CH 3 COOH + 2C0 2.
Glycerin is formed in a small amount during alcoholic fermentation. If the fermentation conditions change, its production can be carried out on an industrial scale.
Glycerin and acetaldehyde are intermediate products of alcoholic fermentation. At the last stage of the normally proceeding fermentation process, a significant part of acetaldehyde is restored to ethanol. But if acetaldehyde is bound with sodium sulfite, then the direction of alcoholic fermentation will change towards the formation of large amounts of glycerin.
The removal of acetaldehyde from the fermented medium with sodium sulfite is presented in the following form:
CH 3 CHO + Na 2 S0 3 + H 2 OW CH 3 CHONaHS0 2 + NaOH.
Acetic aldehyde, formed during the decarboxylation of pyruvic acid, cannot serve as a hydrogen acceptor as a result of binding with sulfite. The place of acetic aldehyde is occupied by phosphodioxyacetone, which receives hydrogen from the reduced NAD-H 2, forming a-glycerophosphate. This reaction is catalyzed by the enzyme glycerophosphate dehydrogenase. Under the action of phosphatase, α-glycerophosphate is de-phosphorylated, turning into glycerol. Thus, in the presence of Na 2 S03, glycerol-aldehyde fermentation proceeds:
C 6 H 12 0 6 \u003d CH3CHO + CH 2 OHCHNOCH 2 OH + C0 2.
Sugar Acetaldehyde Glycerin
With an increase in the amount of sodium sulfite introduced into the fermented medium, the amount of bound aldehyde increases accordingly and the formation of ethanol and CO 2 is weakened.
Formation of acids and acetoin. Succinic acid is formed by dehydrogenation and condensation of two molecules of acetic acid with one molecule of acetaldehyde (hypothesis by V. 3. Gvaladze and Genavua):
2CH 3 C00H + CH 3 CHO -* C00HCH 2 CH 2 C00H + CH 3 CH 2 OH.
In the process of alcoholic fermentation, succinic acid is also formed by deamination of glutamic acid. The hydrogen acceptor in this reaction is trioseglycerol aldehyde, so the deamination reaction is accompanied by the simultaneous accumulation of glycerol:
C 6 Hi 2 0 6 + COOHCH2CH2CHNH2COOH + 2H 2 0 \u003d CO0HCH 2 CH 2 COOH -b
Glucose Glutamic acid Succinic acid
2CH 2 OHCHNOCH 2 OH 3 + NH 3 + CO 2.
Glycerol
Ammonia is consumed by yeast for protein synthesis, while glycerin and succinic acid are released into the medium.
The formation of citric acid, according to Lafon, comes from. nine molecules of acetaldehyde:
9CH 3 COOH + 4H 2 0 \u003d (CH 2 COOH) 2 C (OH) COOH + 6CH 3 CH 2 OH.
Lemon acid
The formation of lactic acid is explained by the reduction of pyruvic acid:
CH3SOCOOH + H 2 -> CH 3 CH (OH) COOH.
Pyruvic Lactic Acid
However, its formation is considered more likely as a result of hydrolysis of the intermediate product of alcoholic fermentation - phosphoglyceraldehyde:
SNOSNONSN 2 OP0 3 H 2 + H 2 0 - * CH 3 CH (OH) COOH + H 3 P0 4.
Phosphoglycerol Lactic Acid
Aldehyde
The condensation of acetic acid with acetaldehyde explains the formation of acetoin:
1) CH3COOH + CH 3 CHO->-CH3COCOCH3 + H 2 0;
Diacetyl
2) CH3COCOCH3 + CH3CHO -4 CH3COCHNOCH3 + CH3COOH.
First, diacetyl is formed; then, by dismutation of the conjugated redox with diacetyl water, acetoin is formed.
When acetoin is reduced, 2,3-butylene glycol is formed:
CH 3 SOSNONSNz + OVER ■ H 2 *± CH 3 CHONSNONCH 3 + OVER.
The mechanism of formation of some secondary products of alcoholic fermentation is not yet entirely clear, but there is no doubt that acetaldehyde is the main starting material for the synthesis of secondary fermentation products.
Acetic and succinic acids predominate among the secondary products, as well as 2,3-butylene glycol and acetaldehyde. Acetoin and citric acid are found in very small quantities.
^ Formation of higher alcohols. Higher alcohols are a peculiar by-product of alcoholic fermentation. The studies of I. Ya-Veselov established that higher alcohols during fermentation occur mainly during the breeding season
Yeast. During this period, the intensity of metabolism is associated with the formation of keto acids from the products of the transformation of carbohydrates with their transamination. Transamination consists in the exchange of CH (NH) 2 and CO radicals between the amino acid And ke-to-acid. So, the formation of alanine from leucine and pyruvic acid is presented in this form:
(CH 3) 2CHCH 2 CHNH 2 COOH -f CH3COCOOH -> CH 3 CHCH 3 CH 2 COCOOH +
Leucine Pyrovinograd- Isonronylgrape
Acid acid
CH 3 CHNH 2 COOH.
Isopropyl tartaric acid, undergoing (similar to
Pyruvic acid in the scheme of alcoholic fermentation) decar-
Boxylation, turns into isovaleraldehyde,
Which is reduced to isoamyl alcohol:
CH 3 CHCH 3 CH 2 COCOOH -> (CH 3) 2 CHCH 2 CHO -*- CH 3 CHCH 3 CH 2 CH.
Isopropyl Grape Isovaleric Isoamyl
Acid aldehyde alcohol
In a similar way, amyl alcohol is formed from isoleucine, and isobutyl alcohol from valine.
Thus, the synthesis of new amino acids occurs with the participation of pyruvic acid, which plays the role of the main bridge between carbohydrate and nitrogen metabolism in the yeast cell.
A number of factors influence the formation of higher alcohols. As the normal fermentation temperature increases or decreases, the amount of higher alcohols decreases. When using the pH of the fermented medium from 3 to 5, the accumulation of higher alcohols increases, and with a further increase in pH, it decreases. Aeration of the medium favors the synthesis of higher alcohols: in the aerated medium, the content of isobutyl and iso-amyl alcohols increases. The introduction of amino acids into a fermentation medium containing sucrose also stimulates the accumulation of higher alcohols. The formation of fusel oil in the culture medium increases with the accumulation of yeast biomass. The content of higher alcohols in the fermentation medium can be reduced by inhibiting the reproduction of yeast.
^ Ether formation. With the participation of yeast esterases, esterification reactions occur, in which alcohol and acids participate. In general, the esterification reaction is represented as follows: RCH 2 OH + RiCOOH -> RCOOCH 2 R! + H 2 0.
So, when ethanol reacts with acetic acid, acetic ethyl ester (ethyl acetate) is formed:
C 2 H 5 OH + CH3COOH 5s CH 3 C0 2 C 2 H s + H 2 0.
The formation of esters proceeds more easily when the components of this reaction are aldehydes. Aldehydes easily undergo redox transformations and give rise to the formation of acids, alcohols, and esters. In this case, all transformations of aldehydes can be carried out as independent reactions without energy consumption.
So, the formation of esters can occur due to aldehydes:
RCHO + HOCRi ->- RCOOCHjRj.
Aldehydes can undergo aldol condensation: CH 3 CHO + C "HzCHO \u003d CH 3 CHOHCH 2 CHO.
The resulting substance contains both aldehyde and hydroxyl (alcohol) groups.
When interacting with alcohol, acetaldehyde turns into diethyl acetal:
CH 3 CHO + 2C 2 H 5 OH - * CH3CH (OS, H 5) 2 + H 2 0.
As a result of the fermentation of sugars and all related processes, the must in brewing and winemaking turns into a finished product (beer, wine). All the substances in it determine its aroma and taste. Thus, higher alcohols (propyl, amyl, isoamyl, tyrosol, tryptopol) have a characteristic odor and give esters that already have more pleasant, softened odors. 2,3-Butylene glycol. and glycerin have a sweet taste.
In alcohol production, the fermented medium is called a mature mash, from which alcohol is obtained by distillation in distillation apparatuses. Ethyl alcohol and CO2 formed during fermentation leave the cells outside into the fermented medium. Alcohol dissolves well in the fermented wort, in any ratio and is evenly distributed in it. COG! it first dissolves in the wort, and as it becomes saturated, it is released in the form of gas bubbles. An adsorption layer of surfactants (proteins, pectin) appears on the surface of the gas bubbles. When individual bubbles stick together, foam cells are obtained. Gradually, the surface of the fermented wort is covered with foam.
The industry produces food and technical ethyl alcohol. Food is obtained by fermentation during the processing of grain, potatoes, sugar beets, molasses; technical - fermentation of wood hydrolysates (hydrolytic alcohol), sulfite liquors or by synthesis from gases containing ethylene.
Alcohol factories produce: raw ethyl alcohol with an alcohol content of at least 88%; the content of impurities is 0.4 - 0.5%; rectified ethyl alcohol of various degrees of purification.
Microorganisms used in production. In the production of alcohol by a biochemical method, the following microorganisms are used:
Yeast. Alcohol production uses baker's yeast Saccharomyces cerevisia ( top-fermenting) or hybrid races of brewer's yeast Saccharomyces carlsbergensis and races of baker's yeast.
Yeast ferment glucose, sucrose, maltose, galactose, raffinose, accumulate alcohol up to 13% vol. The optimum temperature is 30 - 33 ° C. They tolerate the increased acidity of the medium when acidified with sulfuric acid during the purification of yeast in production.
Evaluation of the production properties of pure yeast cultures. The following requirements are imposed on the races of alcohol yeast:
high fermentation activity;
the ability to quickly and completely ferment the sugars of the environment, i.e. the ability to produce low offal;
resistance to high concentrations of alcohol;
resistance to acidification of the environment and to metabolic products of foreign microorganisms.
Mature production yeast entering the fermenters must have the following characteristics:
The number of budding cells is 10–15%;
The number of dead cells is not more than 2 - 4% (an increase in the number of dead cells indicates the presence of factors in the environment that inhibit the vital activity of yeast);
The number of cells containing glycogen must be at least 70%, a decrease in the number of such cells indicates that the yeast is poorly nourished and weakened;
The number of yeast cells in 1 ml of the medium should be at least 120-140 million;
microscopy should not reveal mobile forms of bacteria, and immobile - no more than 4 - 6;
· Races of yeast used for fermentation of molasses solutions must ferment sucrose, glucose, raffinose by 1/3 or completely.
The main factors affecting the vital activity of yeast in alcohol production are temperature, pH of the medium, wort concentration, content of organic and inorganic acids.
Temperature. The optimal growth rate of alcoholic yeast is 30–32 °C, however, yeast grown at a temperature below the optimum has a higher fermentation activity, so the fermentation process starts at a temperature of 18–22 °C, and during fermentation it is maintained at a level of 29–30 °C . A higher temperature causes a decrease in fermentation activity and promotes the development of lactic acid bacteria and wild yeasts.
pH of the environment. Hydrogen ions change the electrical charge of the colloids of the plasma membrane of the cell and, depending on the concentration, can increase or decrease the permeability of the cell membrane for individual substances and ions. The rate of nutrient entry into the cell, the activity of enzymes, and the formation of vitamins depend on the pH value.
When the pH of the medium changes, the nature of fermentation changes: if the pH shifts to the alkaline zone, then the content of glycerol and side substances in the mash increases. The optimal pH for yeast development is 4.8 - 5.0, but in alcohol production they try to maintain it at a level of 3.8 - 4.0 in order to suppress the development of lactic acid bacteria. The required pH is created by adding sulfuric, hydrochloric or lactic acid.
Sugar content in wort. Very high concentrations of sugar increase the osmotic pressure in the yeast cells, while low concentrations are economically unprofitable, therefore, the wort is fermented with a dry matter content, which corresponds to a content of 13-15% sugar in it. Depending on the initial concentration of sugar and production losses, the alcohol content in a mature brew is 8 - 9.5 vol. %.
Lactic acid bacteria. Sometimes lactic acid bacteria of the species are used to acidify the must in the production of alcohol from potatoes and grains. Lactobacillus delbrueckii. The cultivation of lactic acid sticks is carried out at a temperature of 50°C. In the wort, acidified with lactic acid bacteria, the content of soluble nitrogenous substances increases, which favorably affects the reproduction of yeast.
Mold mushrooms. To obtain sugar preparations that are cheaper and more active than malt, specially selected active strains are used. Aspergilus batatae, Asp. Nigeria, Asp. orizae and others. Such fungi are good producers of amylolytic enzymes.
The production of ethyl alcohol by biochemical means is based on the vital activity of yeast fungi Saccharomyces cerevisiae, converting the sugars of the nutrient medium into alcohol, carbon dioxide and a small amount of by-products, some of the sugars are used for synthesis processes during the growth of yeast cells.
The alcohol accumulated in the medium is isolated by distillation; carbon dioxide is captured by special apparatus and converted into liquid and solid carbon dioxide. By-products of fermentation, as well as yeast, are separated and used in technology and bakery.
Raw material preparation . The most commonly used raw materials are:
Depending on the processed raw materials, the technological process has its own characteristics.
Starch-containing raw materials. Starch is a complex polysaccharide. Yeasts do not ferment it due to their lack of amylase. Therefore, starch-containing raw materials must first be subjected to saccharification. However, the starch contained in the cells of a grain or potato is not accessible to amylase. To destroy or weaken the cell walls, the raw material is subjected to high temperature and pressure, resulting in boiling, gelatinization and liquefaction of starch. The next step is saccharification. This is the process of converting gluten starch raw materials into sugars under the influence of saccharifying enzymes. Sources of saccharifying enzymes are malt or mold fungi.
Seed preparation. Yeast is propagated in the yeast department of the plant in compliance with all necessary conditions to obtain pure and physiologically active industrial yeast. Pure culture of yeast is accumulated gradually, in several stages. For yeast propagation, optimal nutrition and temperature conditions are created.
Upon receipt of the inoculum of yeast, a laboratory pure culture is first obtained using sterile malt wort as a nutrient medium with a solids content of 8–10%.
The production stages of breeding a pure culture are carried out on a nutrient medium containing the raw materials that are processed at this plant: grain, potato or molasses. At the end of the production stage, the yeast is transferred to the yeast apparatus or yeast generator. In 1 ml of the medium, the yeast generator should contain at least 150-200 million yeast cells of a pure culture, since with such a quantity, the yeast is more resistant to infection by foreign microorganisms.
Basic fermentation. Yeast from the yeast generator enters the fermentation section of the plant, where the main fermentation process takes place.
There are several methods of fermentation of raw materials: batch, semi-continuous and continuous.
Flow culture methods are more productive. With the continuous method of fermentation, more favorable conditions are created for the vital activity of yeast - constant renewal of the environment, removal of harmful metabolic products and the possibility of maintaining all favorable parameters at the same level. In addition, the advantage of a continuous process is the possibility of its mechanization and automation.
Fermentation takes place in a battery of fermenters, connected in series by communications, through which the brew flows from one apparatus to another. The main fermentation takes place in the first apparatuses, in the subsequent ones, after-fermentation takes place.
Distillation of alcohol and its rectification. The fermented mature mash enters the mash tank, from where it is pumped to the mash distillation apparatus. In these devices, ethyl alcohol and all volatile impurities are separated from the mash. The resulting product is called raw alcohol, and the remainder is called stillage. Raw alcohol is used for technical purposes or subjected to purification from impurities - rectification. Fusel oils, aldehydes and esters contained in raw alcohol are selected during rectification and rectified alcohol of various degrees of purification is obtained.
Extraneous microorganisms of alcohol production.
Microorganisms dangerous for alcohol production, which reduce the yield of alcohol due to the inhibition of the vital activity of yeast by the products of their metabolism, include:
spore-forming bacteria both aerobic and anaerobic, most often it is butyric. When the grain is boiled, the spores do not die, and in the future they can multiply in the saccharified mass and cause its souring. In addition, these bacteria reduce the nitrates contained in molasses to nitrites, which inhibit the vital activity of yeast cells;
yeast Saccharomyces exiguus, Saccharomyces intermedius, yeast-like fungi genera Torulopsis And Candida
heterofermentative lactic acid bacteria. The metabolic products of these microorganisms - acetic and formic acids, esters and aldehydes - have a depressing effect on the fermentation ability of yeast, as a result of which the alcohol yield is sharply reduced.
Beer production
Beer is a low-alcohol drink made mainly from barley malt and hops by fermenting the wort with brewer's yeast.
Characteristics of races of yeast used in brewing. Yeasts used in brewing are of the species Saccharomyces cerevisiae And Saccharomyces carlsbergensis.
Yeast Saccharomyces cerevisiae related to yeast top fermentation and are rarely used, mainly for dark and specialty beers.
Yeast Saccharomyces carlsbergensis carry out bottom fermentation beer wort - settling to the bottom of the fermentation tanks. This yeast ferments well at 5-10°C and is widely used to make standard and varietal beers.
To produce high-quality beer, yeast must have the following properties:
· high fermentation activity. Fermentation activity is determined by the degree of fermentation of the wort (an indicator characterizing the ratio of the mass of the fermented extract to the mass of dry matter in the initial wort).
· flocculation ability- slowly and completely settle to the bottom of the fermenters at the end of the main fermentation. Differences in flocculation properties underlie the division of yeast into flaky And pulverized. Flaky yeast at the end of the main fermentation stick together into lumps - floccules and during the bottom fermentation they settle, forming a dense sediment, and during the top fermentation they rise to the surface. Pulverized yeast remains suspended throughout the entire process.
· moderate ability to reproduce. Very active reproduction of yeast is undesirable, because. at the same time, the extractive substances of the wort are consumed and a large amount of by-products is formed (on average, during the fermentation process, the yeast biomass increases by 3–4 times);
· stability of morphological and physiological properties; The morphological state of yeast reflects their physiological status. The presence of a large number of morphologically altered cells , especially in combination with reduced fermentation properties, is a sign of degeneration of the culture. A large number of cells with granular protoplasm, large vacuoles, and the absence of budding cells characterize the old culture. A high content of dead cells (more than 10%) indicates possible violations of the technological process: slow main fermentation, the development of certain types of foreign microorganisms. Fatness of yeast is determined by the content of glycogen in the cells, and its presence gives an idea of the ability of yeast to ferment. In normally nourished yeast, 70-75% of the cells contain glycogen. A lower number of cells with glycogen in industrial yeast indicates the old age of the yeast cells or their insufficient nutrition.
The main stages of the technological process.
Cultivation of pure cultures of yeast in the brewing industry.
The task of breeding a pure culture is to increase the yeast biomass from the volume of the test tube to the volume introduced into the fermenter.
Breeding a pure culture of yeast is carried out on sterile hopped wort with a solids concentration of 11 - 13%, gradually adapting the yeast to the wort and low temperature. The breeding process consists of two stages: laboratory and workshop.
Preparation of beer wort. Malt and other grain products required by the recipe are crushed to ensure and accelerate the physical and biochemical processes during mashing. Crushed malt is poured into the mash apparatus, into which heated water is first poured. Congestion heated at the required rate with maintaining pauses at certain temperatures. The completeness of saccharification is determined by the iodine test. Then the mash is pumped for filtration into the filtration apparatus. filtered wort and wash water is pumped into the wort brewer and subjected to boiling with hops.
The transformation of barley substances during malting and malt substances during mashing and boiling of the wort occurs under the action of malt enzymes without the participation of microorganisms. Under the action of malt enzymes during mashing and boiling in the wort, the content of fermentable sugars increases, the wort proteins are split first into peptides, and then into amino acids. The biochemical composition of the wort has a significant impact on the vital activity of yeast and the quality of the finished product:
carbohydrate composition determined by the presence of fermentable and non-fermentable sugars in the wort. The content of fermentable sugars in the wort is 70-80% dry matter. These are maltose (60 - 70%), maltotriose (15 - 20%), glucose (10 - 15%). Monosaccharides ferment the fastest, maltose slower, and maltotriose the worst.
nitrogen composition. Nitrogenous substances are necessary for cells to synthesize components that ensure their growth and reproduction. The most valuable and important sources of nitrogen are amino acids, purine and pyrimidine bases. The formation of aromatic substances depends on the biosynthesis and breakdown of amino acids. The amino acids formed during the biosynthesis of yeast give the beer a velvety texture. Under unfavorable cultivation conditions, they can cause yeasty flavors and haze in the beer.
Fermentation of beer wort with yeast. The clarified and cooled wort is fed into the fermentation tank.
The transformation of wort substances during fermentation is a biochemical process caused by microorganisms - brewer's yeast.
Microbiological processes in fermenting beer wort. For fermentation, seed yeast is given at the rate of 0.5 liters per 100 liters of must. The process of reproduction of yeast cells occurs in five stages. In the process of fermentation, the amount of yeast increases by 3-4 times.
The reproduction of yeast begins earlier than the process of alcoholic fermentation caused by them. However, reproduction occurs quickly and ends mainly in 3-4 days, while fermentation occurs during almost the entire stage of the main fermentation (7-10 days) and continues during the after-fermentation period.
The increase in yeast weight during fermentation depends on the amount of yeast given, the amount of extract in the must, the content of dissolved oxygen and temperature. With a small amount of seed yeast, the fermentation process is slower, but the growth will be large. Conversely, a large amount of given yeast provides a higher fermentation rate and a lower biomass gain. For production, the second way is the most beneficial, since it reduces the loss of the extract for the formation of yeast. In addition, reducing the growth of yeast during fermentation can be achieved by removing dissolved oxygen from the wort, since the presence of it accelerates the reproduction of yeast. Under aerobic conditions, the extract is consumed, but alcohol is not formed, and oxidized products accumulate in the medium, complicating and lengthening the last period of beer maturation.
The rate of yeast reproduction depends on temperature: At low temperatures, yeast reproduction slows down, but they grow larger with a large supply of reserve substances and high fermentation activity. As the temperature rises, the need for nutrients in yeast increases, the size of the cells decreases, they do not contain reserve substances and grow weaker.
Many substances inhibit the reproduction of yeast. So, when the content of ethyl alcohol in the medium is more than 1.5%, their reproduction slows down, and at a concentration of more than 3%, the fermentation of wort sugars by yeast slows down.
Mineral and organic acids are also inhibitors: 0.5% sulfuric acid in the medium kills yeast in 1-2 hours; acetic acid also acts when it is contained in the medium in an amount of 1%. However, the content of 1% lactic acid in the medium is tolerated relatively easily by yeast.
Yeast, consuming the nutrients of the wort, increase their biomass. By the end of the main fermentation, due to a 3-4-fold increase in the biomass, the cellular specific surface of the yeast increases, which leads to their sticking (flocculation). When cells stick together, flakes (flocculi) are formed, which is why the ability of yeast to clarify beer is called flocculation or flocculation. In bottom fermentation, the flocculation of the yeast can be controlled to get the right attenuation and leave enough dispersed yeast to finish the beer.
Thus, the end of fermentation is determined by the flocculation of the yeast. The main fermentation is carried out for 5-10 days.
At the end of the main fermentation, a dense sediment consisting of three layers forms at the bottom of the vat. The bottom layer of yeast is formed by old weakly fermenting yeast cells that settle faster than others. The middle layer of yeast consists of the most actively fermenting yeast and large protein flakes, the top layer is formed by small yeast cells with reduced flocculation ability, as well as protein residue and hop resins. To obtain seed yeast, only the middle layer is used.
After the main fermentation, the yeast is separated, washed with cold water and used for industrial purposes, considering them to be the first generation. Production yeast, provided that it has good fermentation properties and is free of microorganisms harmful to beer, can be used up to 10 generations.
Biochemical processes in fermenting beer wort. The wort is fermented to obtain a certain amount of alcohol, corresponding to the type of beer. Most of the sugars in the wort are fermented to form alcohol and carbon dioxide. This is an exothermic process, which is accompanied by the release of heat.
As a result of fermentation, alcoholic fermentation products accumulate in the wort (in % mass): carbon dioxide 0.3 - 0.5 and ethanol 3 - 6, depending on the type of beer. A large role in fermentation belongs to nitrogenous compounds.
The nitrogen composition of the wort during fermentation changes significantly, since about 40% of amine and 60-80% of ammonium nitrogen are used to build the proteins of the multiplying yeast. After the cessation of yeast reproduction, the amount of amine nitrogen in beer may slightly increase due to the release of about 15% of assimilated nitrogen from them, as well as the formation of new amino acids from wort proteins under the action of yeast proteolytic enzymes; the total amount of protein nitrogen in the beer decreases.
During the fermentation process, by-products are formed in beer. Thus, aldehydes accumulate in beer at the beginning of fermentation, then under the influence of anaerobic conditions they are restored and their number decreases. Higher alcohols and esters are formed, which determine the aroma and taste of the finished product, and organic acids, the concentration of volatile substances in beer is very small - about 0.5%, but they participate in the formation of the bouquet - the taste and aroma of the finished product.
By-products of fermentation are four-carbon compounds such as diacetyl, acetoin and 2,3-butylene glycol. Four-carbon compounds, especially diacetyl, have a specific odor (domestic beers contain diacetyl 0.4–1.0 mg/l). By increasing the amount of diacetyl in the beer, a honey flavor appears, which was previously attributed only to a bacterial infection (the "sarcinic disease" of beer).
As a result of biochemical processes occurring in the wort during fermentation, the titratable acidity increases. The concentration of hydrogen ions (pH) in the medium also changes. Changes in pH and titratable acidity lead to a decrease in the solubility of proteins and hop substances. At the same time, part of the proteins precipitates, forming flakes, and hop substances and lighter particles of proteins rise to the surface, forming a “tire”, or deck. A change in the content of nitrogenous substances, phosphates and organic acids in beer leads to a change in the buffering capacity of the medium.
Fermentation and maturation of beer. Young beer is pumped to the after-fermentation apparatus located in a specially cooled room with a temperature of 2 - 3 o C, where it matures at a given temperature and pressure. The duration of fermentation is from 6 to 100 days, depending on the type of beer. The fermentation process is carried out by dusty yeast.
The product obtained at the end of the process is ready for consumption and bottling.
Microorganisms that infect wort and beer. Microorganisms introduced into wort and beer cause various "diseases", expressed in the appearance of a smell and taste that are not characteristic of beer, and a decrease in its quality.
Various microorganisms are found in wort and beer. Some of them come from the air, with malt dust or with grain (epiphytic microflora). Microbes can also be introduced with water, where they enter from the soil with feces. At the same time, pathogenic microorganisms that cause human disease can also enter the wort and beer.
Microorganisms that develop in wort and beer belong to different groups - bacteria, molds and yeasts. They can be harmless, "comorbid" or pests of production.
bacteria. In terms of the number of representatives, as well as the damage they cause and damage to products, the first place belongs to bacteria. Once in production, they gradually adapt to the conditions of the technological process, change and adapt in such a way that the fight against them presents certain difficulties. The harm caused by them is expressed not only in the deterioration of the quality (persistence) of beer, but also in the deterioration of its taste up to complete unsuitability.
Lactobacillus. Lactic acid bacteria are potential pests that cause haze and almost always sour beer. The group includes microorganisms that, during the fermentation of carbohydrates, mainly form lactic acid (homofermentative bacteria). Lactobacillus resistant to high acidity and antiseptic action of hops.
lactococcus. In hopped wort and beer, they form haze, sediment, lactic acid or diacetyl, and sometimes mucus. Cause "sarcine" beer disease distorting its taste and smell. Beer acquires an unpleasant taste and a characteristic honey smell, which is caused by diacetyl formed by pediococci.
Acetobacterium- acid-resistant and develop in a wide range of pH - from 4.5 to 3.2. Since acetic acid bacteria use alcohol and sugars as carbon sources, they find ideal conditions for development in the brewery. May form in beer slime even with a limited amount of air, such as in bottled beer. When they grow in beer, a polysaccharide gelatinous substance dextran is formed. Intensive formation of mucus in beer depends on the content of dextrins in it. At the same time, sugar does not have any effect on the process of mucus formation.
Flavobacterium use glucose and fructose wort. Appears in infected beer silky haze, slight smell of hydrogen sulfide and apples.
Escherichia coli. E. coli is an indicator of the sanitary condition of the enterprise.
Zymomonas. Bacteria are resistant to hop substances and low temperatures. They form ethanol, acetaldehyde and CO 2 . When developing in beer, bacteria give it an unpleasant foreign smell and taste and cause turbidity.
Yeast. In the brewing industry, there are yeasts that can spoil the taste and impair the quality of the beer. With the development of wild yeast in the wort and beer, an extraneous smell, strong turbidity, unpleasant bitterness and taste, and sediment may appear. Wild yeast settles less well than cultured brewer's yeast, making beer clarification and yeast coagulation more difficult. Extraneous smell and taste to beer are imparted by higher alcohols, esters of volatile acids and bitter substances, which are formed by wild yeast.
Saccharomyces pastorianus ferment carbohydrates, give beer a bitter taste, an unpleasant odor, cause cloudiness.
Saccharomysec ellipsoidus. WITH ferment carbohydrates, cause spoilage of taste and turbidity.
Pichia. Volatile acids and other substances are formed in beer, due to which the beer acquires a fruity-ethereal and medicinal aftertaste.
Candida. They develop on the surface of wort and beer in the form of a white or grayish film. Give beer an unpleasant taste and smell.
Candida mycoderma does not ferment sugar. They have a high rate of reproduction and in case of infection are able to accumulate in large quantities.
Torulopsis. May cause haze in beer and impair its taste. The main danger is that dead cells serve as nutrient material for other microorganisms.
In brewing, representatives of several types are found. mold fungi.
Aspergillus- found on damaged grain, on hops, in damp factory premises, in containers and containers, on beer residues.
Oidium- milk mold, found on green malt, in grains, on wet walls of containers in contact with mash or wort.
Rhizopus- black mold. Products affected by mold are covered with white spider-like mycelium. Rhizopus is the most dangerous pest of the malt shop and causes the same harm to malt as Penicillium.
Wine production
Wine is a product of alcoholic fermentation of grape or fruit juice.
The technological process of wine production is based on the biochemical transformations of substances in grape or fruit juice (must) under the influence of yeast, the metabolism of which is regulated by the enzyme complex of the cell.
Classification of grape wines. The classification of wines is made taking into account the grape variety, color, production technology, alcohol and sugar content, aging period.
by color wines can be white, rosé and red.: White Grape wines are obtained by fermenting must from light grapes. Red Wines are made from red grapes by fermenting the must along with the skins and pips. During the fermentation period, the coloring tannins from the seeds and skins pass into the must, so these wines have a red color, astringent, astringent taste. Pink wines are made from white and red grape varieties or obtained by blending (mixing) white and red wines.
Depending on the type of raw material grape wines are produced varietal, obtained from a single grape variety, and blending, made from several varieties of grapes.
Quality and maturity grape wines are divided into ordinary, ordinary aged, vintage and collection. Ordinary wines are released for sale without aging, not earlier than 3 months from the date of grape processing. Ordinary aged The wines are aged for over a year. vintage wines- high-quality, obtained from certain grape varieties. These wines retain their properties regardless of the length of exposure. Duration of exposure - at least 1.5 years. Collection wines- Vintage wines of very high quality, aged for at least 6 years. After aging in barrels, they are additionally aged for 3 years in bottles.
Depending on production technology, alcohol and sugar content grape wines are divided into table, fortified, flavored and carbonated.
Table wines. They are obtained by fermenting grape juice without the addition of alcohol. The alcohol content in them is from 9 to 14%; According to their sugar content, they are classified into dry table wines with a residual sugar content of up to 1%, table semi-dry and semi-sweet wines, sherry. IN dry wines, the fermentation process goes to the end, all the sugar is fermented. They contain up to 0.3% sugar and have a pleasantly refreshing sour taste. Table semi-dry and semi-sweet wines obtained by incomplete fermentation of sugar wort. The fermentation process is suspended by cooling or pasting. After bottling, semi-dry and semi-sweet wines are pasteurized. Semi-dry wines contain 9 - 14% alcohol and 0.5 - 3% sugar; semi-sweet -9 - 13 vol.% alcohol, sugar from 3 to 8%. They have a pleasant sweet and sour taste. Table sherry obtained by aging wine in incomplete barrels under a yeast film (solera). The color of the wine is golden, it has a special taste and a bouquet with a mushroom tone. Sherry is produced with a strength of no more than 14%, not sweet.
Fortified wines usually made with the addition of alcohol . According to the content of alcohol and sugar, they are divided into dessert and strong. Dessert wines obtained as a result of incomplete fermentation of grape must. Fermentation is stopped by adding alcohol to the fermenting must. The alcohol content in dessert wines is moderate, 12 - 17 vol.%. The group of dessert wines includes Cahors, Malaga, Pinot Gris, Muscat, sweet white, red, rosé, etc., which are made from dried or raisined and therefore very sweet grapes. Wines containing more than 20% sugar are called liquor. The higher the sugar content of wines, the less alcohol is required to ensure their biological stability. Fortified wines are different from desserts with a higher alcohol content - from 17 to 20 vol.% and less sugar. The sugar content of strong wines is low - up to 14%. This category includes dry and semi-sweet madeiras, ports, dry, semi-dry and semi-sweet sherries.
A separate group are flavored wines to which vermouths belong. Vermouth- grape wine infused with various odorous materials of plant origin. They include wormwood, from where the name came from (German. Vermuth- wormwood), vanilla, cinnamon, cinchona peel, cardamom, centaury, thyme, yarrow, mint, birch buds, lime blossom, bison, etc.
Special group - carbonated wines: sparkling or champagne and sparkling wines. In France, the name "champagne", according to the law, have the right to wear sparkling wines produced only in the province of Champagne from local grapes and only bottled. Initially, champagne "vino secco" was a sweet wine made from berries that dried up when ripe.
Wine champagne is produced by bottle and tank methods. In the first method, the bottles are aged for 3 years. In this case, the bottles are kept upside down, in connection with which the precipitate forms on the cork, it is removed together with the cork after freezing. Bottled champagne is marked "aged" on the label.
With the tank method, champagne wine takes place in large containers, after which it is bottled, where fermentation continues for another one or two years. Champagne is made in this way in Abrau-Dyurso, at Rostov, Moscow and other factories.
distillation of grape wine cognacs. The birthplace of cognac is the French department of Charente (the center is the city of Cognac), so only the one made in Charente should be called real cognac. This is a strong alcoholic drink made from cognac spirit, obtained from dry white grape wines by distillation. Cognac alcohol with a strength of 65 - 70% is aged in oak barrels or tanks loaded with oak staves. Depending on the aging, ordinary cognacs (aged 3-5 years) and vintage cognacs are produced. The years of aging of ordinary cognacs are indicated by asterisks.
Characteristics of yeast races used in winemaking. The main role in the fermentation of grape and fruit must belongs to yeast. Under the influence of yeast, always present on the surface of ripe berries and fruits (epiphytic microflora), juice fermentation can occur spontaneously (spontaneously).
Grape juice is an excellent nutrient medium. The introduction of wild yeasts and yeast-like organisms into the wort can change the taste and cause spoilage of the finished product. To suppress unwanted microflora and to obtain a finished product in wine production, cultural yeast is used as the main fermentation agent.
Wine yeast belongs to the family Saccharomycetaceae, types Saccharomyces vini And Saccharomyces oviformis. The cell structure of wine yeast does not differ from that of other Saccharomyces cells. The shape and size of cells in S. oviformis And. S. vini are the same.
Yeast Saccharomyces vini ferment glucose, fructose, mannose, maltose, sucrose, galactose and a third of raffinose; do not ferment lactose, pentoses, dextrin and inulin.
Saccharomyces oviformis - also reproduces well in grape juice and yields about 18% alcohol. On the surface of dry grape wine, they form a film. They are used in winemaking for the production of sherry. Yeast can ferment glucose, fructose, mannose, sucrose, maltose and a third
Alcoholic fermentation- the foundation and the beginning of all drinks containing alcohol, whether it be wine, whiskey or beer. The basis of this very foundation is raw materials, water and yeast. In this article, we will cover the different types of wine yeast used in home and industrial winemaking. Let's consider what kind of yeast are - friendly, helping to develop the richness and diversity of wines, and hostile to the winemaker, oppressing and spoiling not only the wine itself, but also infecting entire wineries along with the equipment.
Alcoholic fermentation (aka “fermentation”) is a biochemical process carried out by yeast, the ideal result of which is the conversion of saccharides (mainly sucrose, glucose and fructose) into ethyl alcohol (the main product), carbon dioxide and many chemical trace elements (necessary and not useful, harmful, and beneficial by-products).
Yeast- microscopic unicellular fungi. Modern microbiology divides them into more than one and a half thousand species and another thousand subspecies, and they, in turn, can reproduce many variations - depending on the results of controlled and uncontrolled mutations and rebirths (you must have come across this yourself if you used one and the same yeast several times, propagating them independently).
Since ancient times, man has adopted alcoholic fermentation, but the food industry and science are still discovering more and more new possibilities and features of using yeast to produce ethyl alcohol. A lot of efforts are concentrated precisely in the development of the winemaking market and the microbiology associated with it, this is a whole industry - oenology. Oenology is engaged in the study and breeding of bacteria, the development of enzymes, the research and reproduction of yeasts that have the qualities necessary for winemakers, allowing the production of many wines and wine drinks, discovering new facets and tastes, as well as preserving old and rare ones that have become the historical heritage of mankind.
The main types of yeast (saccharomyces - they are the friends of all alcovars - winemakers, brewers and moonshiners) used in the production of alcoholic beverages (including at home).
Table for clarity. Here are some races of yeast, variations of which (different strains of the same species) are popular in industrial (and some in home) winemaking. Please note that the choice of a particular race is determined, among other things, by the conditions of fermentation. Some races of wine yeast recommended for winemaking are shown in the table (some of their foreign analogues are available for purchase in our store).
"Saccharomyces cerevisiae"(Saccharomyces cerevisia) is the most common, diverse and "tamed" type of yeast currently in the world. It is the various races of this type of Saccharomyces that are leaders in the field of bakery, wine, beer and alcohol yeast. They are so diverse, and their scope is wide, that they deserve a separate article. Unfortunately, they are not always encountered in wild winemaking, and considering that among Saccharomycetes cerevisia there are hundreds of subspecies negatively (to one degree or another) affecting wine, the probability of "successful infection" becomes even lower, but not absent;
"Saccharomyces vini"(Saccharomyces blame) - they mainly live on ripe (and especially on damaged) grapes and in juices (uncovered from external influences). Often they can be found in the soil, in the digestive system of insects (especially fruit flies, wasps and bees), as well as inside the wine industry (including home wineries) - on walls, utensils and equipment. However, in home winemaking they are used very limitedly, they can have many undesirable effects - for example, clouding of the wine and the formation of suspension;
"Saccharomyces oviformis"(Saccharomyces oviformis) - most often the use of this race in winemaking can be beneficial. They are used to ferment musts with a high sugar content and are well suited for the production of dry wines. Modern representatives of this yeast race are popular in the production of champagnes.
There are also domestic races: “Leningrad”, “Kiev”. The disadvantages of using these strains may include re-fermentation in the finished wine (most often semi-sweet, but not exclusively), as well as turbidity and the formation of late sediment. The most productive use of these strains for the production of sherry - fortified wine. Representatives sharpened for this (a variety called “ Oviformis Cheresiensis”) - “Jerez 96-K” and “Jerez-20-S” - however, they very quickly generate a film on strong wine (16-17% vol.).
"Saccharomyces bayanus (uvarum)"(Saccharomyces bayanus uvarum) - most often they can be found in fruit wines and juices. This is a very leisurely yeast - it develops slowly, the mutation is difficult to control due to the microbiological processes that are difficult to distinguish for the current level of control in home winemaking. They are not yeasts with a high degree of attenuation (alcohol formation), but they have a rare feature - increased stability and resistance to cold. As for the products of fermentation, they are almost identical to what the aforementioned yeast strain produces. S. Vini. Features - many (but not all) races of this variety are able to form the densest (not amenable to resuspension) yeast sediment, the foam is almost completely absent, they give an increased content of glycerin. Of the most popular races - "Novotsimlyanskaya 3", while it is almost inaccessible for home winemaking, but has proven itself well for the production of semi-sweet wines.
But not all yeasts are the same. Next, consider a few dangerous and vile enemies of winemakers - yeast, which has completely unfriendly properties.
"Pichia"/"Hansenula"/"Candida" and other filmy are serious enemies, pests and culprits of failed wines (especially when using wild yeasts). Their main feature is the formation of a film on the surface of the wine, especially under aerobic conditions ( water seal (water seal) to help). The cells of these harmful yeasts have an unstable shape - there are elliptical, oval, sausage-shaped and club-shaped forms and disproportionately elongated. Some of them (Pichia and Hansenula) form spores, while others reproduce by budding. These races are capable of fermenting wine must at high speed, oxidizing it. Some of them cannot produce enough alcohol for modern wine, for example, Hansenula - gives only up to 5% ethanol.
In a properly prepared wort, they are usually not dangerous, because. are contained in small quantities. If you comply with the technological conditions for the preparation and storage of wine materials (tightness, sterility of the material and the surrounding atmosphere), from which the wine will be made, there is nothing to fear. But with poor preparation (beginner/ignorant winemakers like not to wash the grapes (not knowing its microflora), use unprepared water and containers) - the strain quickly begins to multiply on the surface. This leads to the creation already for 2-3 days (sometimes later) of a glossy, and then a folded (pimply) film, which can be in a wide color range - from white and dull-transparent to gray.
If the wine is suddenly infected, then the film is not the worst. Film formation signifies a new stage of fermentation - fermentation with sugar oxidation. In the process, not only ethyl, but amyl and butyl alcohols, as well as acetic, butyric, succinic acids and various ester compounds of these acids are necessarily formed. As a result, the wort gets a characteristic very unpleasant odor. The probability is especially high if you use pulp - then the most favorable conditions come for races like Pichia / Hansenula (therefore, we recommend using stronger fruit and alcohol yeast for the production of chacha, which can level this process).
Some filmy yeasts (often found in wild fermentation - can be conversely very alcohol-resistant (and also sulfite-resistant), which some unlucky winemakers like at first. They can feel comfortable even at an alcohol content of 14% vol. and 400-500 mg / l SO2. For the same reason, in table wines (to which there is access to oxygen) they will feel very comfortable, gradually forming various impurities that lead to deterioration of wine (especially homemade and unfinished wine without preservative). They restore very quickly sulfates and sulfites, while generating a high content of hydrogen sulfide and various sulfur compounds, this is the cause of an unpleasant rotten smell.
Blossom is one of the most common wine diseases that gives an unpleasant appearance (precipitation, suspension, islets, haze) and an unpleasant smell, often due to the presence of active yeast of the aforementioned races and breeds in the must. In addition, they are the worst enemies of the production of dry wines, champagne and sherry - be careful!
The development and reproduction of malignant yeast in wine can be prevented by limiting the access of oxygen to it (again, a water seal) and by setting the right conditions for storing wine material - low temperatures, and the containers themselves must be completely filled - without leaving a lot of free space. Sometimes timely topping up may be required - do not neglect this.
"Zygosaccharomyces"- another representative of the harmful (for the winemaker) microflora. This race of yeast is very osmophilic - they feel great in extremetea-sweet wort, develop even with a sugar content of 60 and even 80 grams per 100 ml. (vacuum fermentation of the wort, various homemade preparations - honey, jams, preserves). They cause the fermentation process in such extreme conditions (imagine what an incredible hydromodule it is) and thereby drastically spoil the product. Paradoxically, this strain is not very alcohol-resistant - they form on average no more than 10-11% alcohol, while they ferment for an extremely long time, but during this time they manage to completely spoil the once suitable material / product. However, modern science has also found their use, though limited - "Race Vierul, Maikopskaya, Krasnodarskaya 40" - can be used to reduce acidity in very sour wort, because. process the material mainly by fermentation, not oxidation (like other harmful ones).
"Saccharomy codes"- regular pests of ancient and modern winemaking. These are complex yeasts that have a large form and an unstable type of reproduction - they can both divide and bud. They have an alcohol resistance of up to 12% (and according to some reports up to 14%), and the wort itself is enriched with ethyl acetate, which has a detrimental effect on the survival of pure yeast cultures and can cause various side effects (for example, a sudden resumption of fermentation).
Saccharomycodes ludwigii- can cause the resumption of fermentation even highly sulphated wort (not all preservatives are a panacea). They also withstand very high SO2 content in finished wines and musts.
"Hanseniaspora"(apiculatus) - an extremely common yeast that can be represented as both sporogens (Hanseniaspora apiculata) and asporogenic fungi (Klocker apiculata). If the fruit is damaged, it is very likely that they are already there, do not disdain juices and large fruits (and small ones too, just a little less often). Fun fact: when grapes ripen, they can reach up to 99% of all the yeast that is there (another reason to be clean - wash the grapes and all wine material!). The fermenting ability is low - only about 4-7% vol. alcohol, however, volatile compounds, ethyl acetate, butyric, propionic and other acids accumulate a lot. Often they are the reason that the must or wine (especially homemade) is not fermented. They have explosive growth and multiply very quickly in the must, several times faster than the growth of other yeasts - especially noble ones. They give the wine bitterness, a lot of extraneous and at the same time strong odors, as well as acetic shades. Did you make homemade champagne or sherry and got “sticky” leftovers? This is also their work. Sulfitation (sometimes increased) and long-term settling can help.
"Torulopsis"- a common race harmful to winemaking, especially when it comes to grapes. They actively stand out in the already fermented grape juice, which began with wild yeast (the so-called noble rot). They can be divided into two main species (T. bacillaris and T. candida). In recent years, there has been information that they form spores, but at the moment it is generally accepted that they reproduce by budding. They do not often appear in wine, but a frequent guest in grape juice. Capable of fermenting wort up to 12.5% ethanol turnover. In terms of biochemistry, they are not as harmful and destructive as other yeasts that manifest themselves during wild fermentation, they form much less harmful chemical elements, but they form - mucus. Agree, few people will be pleased to drink wine, in which in some places there are islands resembling jelly or something even more slippery. They are also osmophiles (they feel good even if the sugar content is 60-80 grams per 100 ml) and love high temperatures, and the increase in SO2 is not at all noticeable for them.
Rhodotorula- this is the so-called "pink yeast", they are so called because of the characteristic color. They do not ferment sugars, but oxidize them, thus creating a dense pink film. They contribute to the oxidation of juices, the formation of turbidity and the precipitation of dessert and semi-sweet (well, sweet) wines. An interesting feature is that they can feed on alcohol vapors in the air, for this reason they often find themselves “red-handed” on the walls of wineries and even cellars in the form of pink slime.
Instead of output:
Under industrial conditions, spontaneous fermentation can cause undesirable consequences. To avoid this and obtain good quality wine, fermentation is carried out on pure cultures of specially selected yeast races, introducing them into the must for a directed process. In modern winemaking, it is still quite common to stumble upon neutral and suitable yeast for winemaking, they may not be true (ideal, like pure yeast cultures), but they will not spoil the wine. For this reason, it cannot be unequivocally assumed that spontaneous fermentation will necessarily lead to spoilage of wine, but this possibility always exists and sometimes this probability can categorically increase. For example, if harmful killer yeast is found on one bunch of grapes, during fermentation they are able to destroy sensitive ones with great speed (1 killer cell can kill an average of 20 noble cells). In addition, there are evilly neutral (not participating in intraspecific struggle) races that can saturate the wine with unnecessary chemical compounds, usually smelling bad.
The use of wild yeast is often fraught with unkindness - suddenly the wort stops "boiling" or a "different fermentation" (filmy) begins. Therefore, if you categorically use wild yeast - add sulfur dioxide , noble strains are usually resistant to sulfitation, and harmful yeasts are usually not (but, unfortunately, not all)
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Mentioned products in our .
1. ale, that is, top, warm fermentation;
2. lager, that is, grassroots, cold fermentation.
Such names have been assigned to brewer's yeast due to the fact that during the fermentation process, yeast behave differently and, accordingly, are divided into powdered and flaky. Pulverized yeast particles are always isolated from each other, and therefore, at the end of the fermentation process, they remain on the surface of the fermentation vessel. Particles of yeast of the second type have a flaky appearance. The shells of their cells in the process of fermentation stick together with each other, settling at the same time on the bottom of the vessel in which fermentation takes place.
Both types of yeast are composed of microscopic single-celled fungi. The former contains a fungus that scientists have named Saccharomycetaceae cerevisiae and is used in Berlin lager beers and many dark beers, particularly porter. Since dark beers are most characteristic of the UK, the yeast was called ale, using the name of the beer in the country. This type of yeast, in the process of fermentation at a temperature of about 14-25 degrees, first forms a white tender foam on the surface, which darkens for some time, becomes denser and forms, as it were, curls of brown color. Then the foam turns yellow, and the curls fall apart. Some of the yeast cells precipitate, and those that remain on the surface are removed along with the foam. The second type of yeast contains a fungus called Saccharomycetaceae carlsbergensis and works best at temperatures of around 6-10 degrees and below. This type of yeast ferments more slowly than ale, but they can be easily removed, as they precipitate during the fermentation process, which is why they are called grassroots or lager by the name of the beer for which they are used. Sales statistics show that beer brewed with bottom-fermenting yeast occupies approximately 90% of the world market.
The fermentation activity of yeast is characterized by the degree of fermentation of the wort, which is calculated by determining the numerical value of the ratio of the amount of fermented extract to the amount of solids present in the initial wort. Professionals classify yeast according to the degree of fermentation as follows:
Highly attenuating with a degree of fermentation ranging from 90 to 100%;
Medium fermentation - from 80 to 90%;
Low fermentation - less than 80%.
Different types of yeast obtained from a single cell are called strains or races. In practice, a great many races are used, each of which has its own name or designation. Thus, yeasts of the following modifications belong to highly fermenting races:
Race 11, very undemanding to the quality of the raw materials used for the preparation of beer, settles well and allows the beer to acquire a full taste. This is the only strain that immediately starts to decompose maltose, while other strains decompose glucose first;
Races 34 and 308 are known for high fermentation activity, but are extremely capricious regarding the raw materials used for making beer;
Race F (Czech) is characterized by the ability to clarify beer well, give it a pleasant taste and is resistant to infections and autolysis;
Race 8aM is distinguished by high fermentative activity, increased multiplication factor, and good settling rate;
Race F-2 can ferment low molecular weight dextrins and maltothetrose, thereby deeply fermenting the wort;
Races 4, 70, 129 should also be mentioned in this series.
The following strains of yeast are classified as medium-fermenting races:
Race A (Riga) perfectly clarifies beer and is resistant to infections;
Races 41, P (Czech) and S (Lviv) settle well and give the beer a mild taste;
Race 44 is most often used when using hard water;
Race 776 is applied when unmalted materials are used;
Race 131-K cannot ferment lactose, sucrose and raffinose, and therefore it is used only in the production of dark beers with a sweet taste.
Some beers are made using a mixture of different yeast strains. Each individual strain is stored in a sterile tube with some hopped wort-agar, that is, a solution created from a liter of beer wort and 18-20 grams of agar, at a temperature of +4 degrees. It has been established by practice that about half a liter of bottom-fermenting yeast is required to ferment 100 liters of wort. But when using top-fermenting yeast, they will need half as much for the same amount of wort.
The chemical composition of various strains is also very diverse and is characterized by the content of potassium (about 2400 mg per 100 g of dry matter), phosphorus and calcium (about 200 mg), as well as relatively small amounts of magnesium, manganese and zinc. The liquid content of yeast is approximately 75% by weight. Microorganisms that make up the yeast, scientists refer to anaerobes, that is, viable with very small amounts of oxygen in their habitat. When placed in an oxygen-containing environment, their active reproduction begins. If they are placed in an environment with a low oxygen content, then the microorganisms contribute to fermentation, as a result of which alcohol is released. This property of yeast is the basis of the beer brewing process. Thus, by understanding the role of yeast and taking into account the peculiarities of using different strains, it is possible to brew beer of different varieties, colors and, most importantly, tastes.
In the manufacture of any modern wine, wine yeast is necessarily used. They go through the following stages in their development:
- Lag stage. It begins from the moment when the yeast grains enter the wort - into the nutrient medium. Cells begin to adapt to the substrate. They increase in size, but at the same time there is no reproduction process yet;
- The second stage is called logarithmic. During it, the cell population increases, and the biomass becomes larger. Cells endure all negative environmental factors. Alcohol fermentation begins;
- The third stage is called stationary. Yeast cells stop growing, and alcoholic fermentation occurs with intense force;
- The fourth stage is the attenuation of the growth of yeast mass cells. The mass begins to decrease in size due to intensive autolysis and the use of reserve substances by yeast.
Having passed all four stages, the yeast mass will make any wine tasty and aromatic.
All about wine yeast
In nature, yeast forms on the surface of berries, such as grapes. They can be easily seen, as they have a light coating on the peel of the berries. Plaque is formed due to the work of a yeast fungus.
Baking, alcohol, beer and wine yeast grains are classified as industrial yeast. Given the place of origin, the grape variety and the location of the vineyards, each type of yeast is assigned its own name. Yeast races, in turn, can be divided into groups. As a result, the races of wine yeast are:
- High fermentation;
- Heat-resistant or cold-resistant;
- Alcohol resistant;
- Sherry.
Alcohol-resistant yeast races are used to make champagne, and sherry to give wines a unique aroma and taste.
Wine is usually made from the juice of grapes or other types of fruits and berries.
If artisanal winemaking takes place, the must (squeezed juice) begins to ferment without the help of yeast, as yeast fungi that are present on the surface of the berries themselves begin to multiply intensively. At the same time, lactic acid, acetic acid bacteria, yeast-like fungi come into force, which can lead to spoilage of the product, or to the production of wine vinegar instead of wine.
For this reason, during the industrial production of wine, in order to avoid spoilage of wine materials, an activated mixture of wine yeast is added to the grape juice.
The type of wine depends on how the fermentation takes place. Thanks to wine yeast, sugar, which is part of the grapes, begins to ferment. Fermentation continues until all the sugar has been converted.
With a lack of oxygen, due to the influence of yeast, alcohol is obtained. If oxygen is constantly supplied, sugar is completely oxidized and water with carbon dioxide is obtained.
During the initial stages of yeast development, fermentation occurs intensively, because of this, the carbon dioxide that is released does not allow atmospheric oxygen to penetrate to the surface of the wort. When fermentation is over, it is important to seal the barrel of wine well. If this is not done, the acetic acid bacteria will convert the alcohol into acetic acid. Instead of wine, you will become the owner of wine or apple cider vinegar.
In the industrial production of wines, grape juice with a sugar content of 25 percent is used.
To obtain white wines, the grapes are peeled and pitted. For red wines, the skins and pits are not removed. Yeast for wine, along with sugar during fermentation, juice is processed into alcohol. Yeast substances give the wine aroma and pleasant taste. After fermentation, lactic acid bacteria play an important role in giving the drink a smell.
Different varieties of wines have their own characteristics of production. For example, to get champagne, fermented wine must be fermented again. The fermentation of the drink must end in a closed container, as carbon dioxide must accumulate inside.
To get a strong wine (sherry), you need to use special sherry yeast, which is resistant to a high concentration of alcohol in the wine material.
Varieties of wines
Wines are dry, sweet and fortified. To get a dry wine, it is important to stop fermentation immediately after the end of the supply of sugar in the squeezed grape juice.
Sweet wines are made by partially fermenting sugar when a toxic alcohol level for wine yeast is reached.
Fortified wines are additionally filled with alcohol.
From the above, we can conclude that the type of wine directly depends on how it is produced, as well as what type of wine yeast is used to ferment the juice.
What are yeast
There are many different types of wine yeast. For example, wine yeast Lalvin KV-1118, Lalvin EC-1118 and others. Let's take a closer look at the instructions for using each type of yeast.
First view
Wine yeast Lalvin KV-1118 is a pure, highly active yeast concentrate, which is used to make light white wines, red wines and champagnes. Also, with the help of such yeast, fermentation can be restored.
Yeast mass is usually used at low concentration, low temperatures, low content of fatty acids. They do an excellent job with their mission in a temperature regime of 10 - 35 degrees. If water is added to the wine material at a temperature below 16 degrees, esters will begin to be produced, which will give the drink a rich aroma. Due to the pronounced killer effect, yeast grains well suppress the "wild" microflora.
Instructions for use of such a product says the following:
- KV-stamped yeast is used to express grape aroma in white, rosé and deep red wines;
- Given the type and purity of raw materials, the conditions and duration of fermentation, the required dosage is determined. Usually it is from 1 to 4 g/dal;
- They do not contain any additives. They have a moisture content of 6 percent;
- Wine yeast (5 grams) is diluted in water (50 milliliters) 34 - 39 degrees. In order for them to work properly, it is important that the water temperature is no more than 40 degrees. Then the mixture must be mixed well to break up the lumps and withstand no more than twenty minutes. After a while, mix again, and slowly pour into the wort. Slow introduction helps the yeast to gradually acclimatize and not die when combined with cool wort;
- Wine yeast can be stored in a dark, dry place for up to a couple of years. Storage temperature should be between five and fifteen degrees. If you open the package, it has a shelf life of no more than six months.
Second view
Wine yeast mass Lalvin EC gives red and white wines a refreshing taste and purity. They ferment well even at the lowest temperatures, forming a sediment in one place. Thanks to this type of raw material, fermentation can be restarted. It is recommended to use it for, as well as from viburnum, hawthorn and cherries. An EC-labeled product has low foaming, clarifies wine well and collects sediment compactly. The instructions for use of EC stamped yeast say the following:
- 300 grams of the contents of the bag should be poured into five liters of forty-degree water. Stir thoroughly until smooth;
- When the temperature of the mixture reaches 35 degrees, carefully pour 250 grams of yeast onto the surface. Let stand 20 minutes and mix well. Then pour the resulting mass into the wort, so that the temperature difference is not higher than ten degrees;
- You can store them in a closed package at a temperature of no more than eight degrees Celsius.
Making wine from grapes is not very difficult. It is only important to purchase the right yeast and carefully study what the instructions say. It usually has everything written on it.
Now you know what wine yeast is. What types are they. How can you get different types of wines using different types of production. Wine lovers are always proud of their creations, especially if people around them like them.
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