Extraneous taste in beer, reasons. How to Avoid Beer Contamination

In this article, I intend to collect material on beer contamination, as it accumulates, and discuss relevant problems in the comments.

About films on the surface

Figure 1. Flask with "problem" wort.

This flask was sterilized with a siphon and silicone tubing in an oven (180 degrees dry heat) and a 0.2 micron sterile sanitizing filter was placed on the flask. Then, using a sterile piece of hose, the flask was connected to a CCT test tap (1200 liters, in one of the breweries in our region). In this case, a gas burner was used - all connecting fittings were burned. All these precautions have been worked out and give a 100% result in terms of sterility. A portion of the wort was poured into the flask, which was boiled with hops for more than an hour, the wort flowed through the sanitized pipelines to the sanitized CCT. Both were treated with a good deinfectant - a solution over acetic acid. The result can be seen in the next photo.

Something has grown in the flask

Figure 2. Something has grown in the flask.

After such an impressive list of antimicrobial measures, the first impression of what you see in the flask is “mold”. (Only mold spores can survive all of the above.) However, this impression may not be entirely correct, or not at all correct. The mere fact of the formation of a surface film on a liquid substrate is not yet sufficient to identify a microorganism as a mold. Earlier, in the article Microbiological aspects of home brewing in the Contaminants section, a table was given that excludes the development of mold in beer. (This table was published in a very serious scientific publication and cannot be in doubt). However, in this case we are not dealing with beer, but with wort, so it is impossible to exclude the development of mold. What is the nature of the formation shown in the photo?

It is possible that at the brewery where the wort sample was taken, some of the above antiseptic measures were either done carelessly, or some unaccounted for factors (for example, rinsing with water of dubious quality), which lead to the development of traditional contaminants long described in the microbiology of beer, such as wild yeasts. (The sterility of the flask is beyond doubt, since I have been storing wort in similarly sanitized flasks for more than a year). Indeed, it turns out that many wild yeast can form films on the surface of beer or wine.

Why do they appear? What does it look like? What does it taste like? Where does it come from and in what situations does it manifest itself? Bacteria are micro-organisms that can (and should) be present in many foods (e.g. yogurt, marinades, soy sauce, sauerkraut, etc.). When it comes to brewing, there are several types of bacteria to watch out for, as once they get into the beer, they can marinate it for up to 24 hours. Perhaps the most common of these is lactobacilli. It oxidizes beer with lactic acid. Another type of bacterium, Pediococcus, is very fond of wort and gives it bad smell and taste. A lesser-known but no less annoying acetobacterium uses acetic acid to turn alcohol into vinegar. Bacteria make beer cloudy, gassy and moldy, and also affect the taste of the drink, giving it strange, bizarre and undesirable aftertastes.

HOW TO DETECT: To quickly and accurately determine if a beer is contaminated with bacteria, take a closer look at the bottle with the conditioned drink. Look closely at the surface of the beer where it meets the walls. Do you see the ring around the neck from the inside? I've learned to identify gassy, ​​cloudy, and sour beers from this ring, as it's a sure sign of a bacterial or yeast infection. Sometimes you can see two or three rings at once, depending on the amount of beer; dirt will remain inside until the bottle is properly cleaned and sanitized. And if the dirt is in bottles, then most likely it is in the siphon tube and in the fermenter. But don't despair. It's never too late to fix things.

Find the source of the bacterial infection home beer not easy, because bacteria are everywhere: on your hands, on the surface of the table, on porous and scratched surfaces, in grain and grain dust (so do not crush grains near the boiler!). Therefore, if there was a problem of infection, it means that the beer came into contact with something poorly disinfected. Bacteria just love malt. They will most likely prefer it to anything in your home. In hospital laboratories, malt extract and gelatin are specifically used for biological research. And bacteria love warmth. And you'll get yourself in trouble if you don't take care to protect your beer in case you happen to brew it in summer heat. Keep safety in mind and you'll be fine.

SOLUTIONS: Below are a few simple tips to improve the quality of the beer.

1. Check bottles for bacterial rings on the inside of the neck. Soak the bottles and fermenters overnight in a solution of 60 ml bleach mixed with 19 liters cold water. This will help remove the rings and kill bacteria. Disinfectants sold at the homebrew store can also come to the rescue. Please consult the seller on this matter. But you can be sure of the effectiveness of ordinary household bleach. At the end of the cleaning procedures, flush the equipment hot water.

2. Under no circumstances should there be bacterial rings on the siphon tube. Disinfect it with bleach or other disinfectants. If this does not help, stop using such a tube in brewing beer.

3. Observe sanitary standards at all stages of the brewing process, especially when the temperature of the wort drops below 71°C.

4. Bacteria can accumulate in cracks on the surface of the plastic bucket. Discard old, stained and scratched fermenters and siphon tubes.

5. The wort should not come into contact with anything other than disinfected glass containers, spoons made of of stainless steel or enamelware. Wooden spoons, plastic stirrers and especially hands are strictly prohibited!

6. Before starting the transfusion, fill the siphon tube with water. But if you're a traditionalist, swish the pipe with brandy or malt scotch before putting it in your mouth.

7. Wash the secondary fermenter immediately after use.

8. Remove stains and sediment from bottles with a bottle brush and a small amount of bleach.

9. Use the water seal correctly. Fill it with water 2.5 cm.

10. Don't ferment your beer too long at 16°C. Two to four weeks in this mode is usually enough, then the drink must be poured into a second fermenter and continue to ferment it at room temperature.

11. Rinse bottles as soon as they are empty.

12. Boil the primer with a small amount water.

13. Boil beer caps or disinfect them with vodka.

14. Cool the wort and add yeast to it as quickly as possible.

15. Shake chilled wort to promote good fermentation.

16. Pour beer carefully. DO NOT SPRAY OR SPLASH IT ON THE SIDES WHEN FERMENTATION BEGINS.

17. Never add ice to the wort if you want to cool it down.

18. Avoid using for secondary fermentation low quality plastic containers. They are difficult to disinfect, in addition, they let air through.

LATEST RECOMMENDATIONS
If you're already making great beer, then you're good. Beginners usually don't have problems with contamination, as there is simply no chance for bacteria to get into the beer. But sooner or later you may miss something. The recommendations above are intended for those who have encountered this problem, but for beginners, the information can be an excellent recommendation for the future.

On the varieties of lactic acid bacteria and their effect on beer.

Photo: Agencia ID

Pediococcus (Pediococcus) is a genus of lactic acid bacteria belonging to the Lactobacillacea family. They are facultative anaerobes and therefore use aerobic respiration for energy when oxygen is present, but switch to fermentation when oxygen is scarce or absent.

Pediococci use glucose to produce lactic acid, however, metabolic end products vary depending on conditions, and typically pediococci in beer produce diacetyl as a major by-product. The genus Pediococcus consists of the following types: P. acidilactici, P. pentosaceus, P. damnosus, P. parvulus, P. inopinatus, P. halophilus, P. dextrinicus and P. urinaeequi.

Pediococci, like several other lactic acid bacteria, have been used as a probiotic for many years, as a preservative for food products, such as sauerkraut, kefir, soy and smoked sausages, and also as a flavor enhancer in some cheeses and yoghurts. They are used in the production of oil, as well as to improve the taste of wines (eg Chardonnay) and cider. Pediococci are also the main ingredient in lambics and can be used either as the sole modifier or mixed in sour beers along with other lactobacilli.

In addition to their acid-producing properties, lactic acid bacteria also produce antibacterial proteins known as bacteriocins, which act as affective preservatives, and since the safety of chemical preservatives has been questioned, as healthy alternative he considers the use of lactic acid bacteria and their metabolites.

Photo: Ryan Opaz

There are about 20 types of lactic acid bacteria that harm beer, of which Lactobacillius brevis is the most common, but Pediococcus species and especially P. damnosus can also be a serious problem. Pediococcus damnosus was originally called Pediococcus cerevisiae. Another species of pediococcus, claussenii, has recently been described as a beer pest, along with Pediococcus inopinatus.

About 60–90% of beer contamination cases are associated with lactic acid bacteria, among the most common of which is Pediococcus damnosus, which accounted for about 3–31% of infections per year from 1992 to 2002.

Beer contamination with P. damnosus is often characterized by the formation of diacetyl along with lactic acid, and the amount of diacetyl is often very high and detectable even at low bacterial levels. Because of its ability to grow even with low temperatures, infection can occur during the fermentation and maturation stages, as well as in bottles. Pediococcal contamination is also a problem when adding yeast because the bacteria bind to the yeast cells and are difficult to remove.

Pedicocci are difficult to detect using traditional methods, often requires the use of specialized media, due to their tendency to grow at low temperatures, optimum temperature culture is 22–25 degrees. Therefore, at present, new types of liquid media are widely used for their detection. This type of chromogenic media changes color depending on the bacteria's ability to produce lactic acid, making detection easier and faster. Other methods for detecting lactic acid bacteria include detection of the gas produced by the bacteria (SpeedyBreedy) and detection of Pediococcus DNA (BrewTek). Like other lactic acid bacteria pests, pediococci are perfectly adapted to the brewing environment, and certain elements of the brewing process actually promote the growth of these bacteria.

Several factors are critical for the inhibition of pediococci in beer, of which pH and hop acids are some of the best known: low pH promotes antibacterial effects on hop acids, but it has also been found that a small increase in pH (0.2) can reduce the effectiveness hop acids by as much as 50%, and therefore careful monitoring of pH can help reduce the chances of beer contamination.

Allagash Brewing Pick Your Own is a sour ale fermented with lactobacilli and pediococci. Photo: Allagash Brewing

Level carbon dioxide is also critical in reducing the likelihood of pediococcal infection: beers with low CO2 levels have been found to be particularly susceptible to infection, such as in the case of nitrogen carbonated cask ales. However, such beer can be consumed even before the infection becomes apparent.

Because beer-contaminating bacteria can be difficult to breed, and beer contamination can often be caused by mixed bacterial cultures, often only bacteria that are easier to grow can be identified. In addition to this, some bacteria that will be obtained in a laboratory environment may not lead to contamination of the beer, and the brewer must rely not only on the opinion of the microbiologist, but also on his own experience.

Either way, the detection of contaminants means that even if the type of lactic acid bacteria in the beer is not known, the brewer will at least know whether the bacteria found are pests or not. The advent of DNA technology means that species carrying the genetic signature of an infestation can be quickly and accurately identified, even if they have not yet been described in the literature. These genes, called horA and horC, provide protection against the antibacterial effects of hop acids and are therefore critical for the survival of bacteria.

Breweries are high in sugar, protein and carbohydrates, as well as vitamins and minerals. It is humid and warm here, it is an ideal habitat for bacteria. However, in addition to this, there are antibacterial hop acids, alcohol and low pH levels. Therefore, bacteria in a relatively short period of evolution (about 100 years) were forced to develop resistance and maintain it in the form of hop-resistant genes.

If your wort gets infected, then the beer will turn sour. At the same time, souring may not happen quickly. This process can drag on for a month, or even two ... To prevent this from happening, you need to take some steps that will help prevent contamination of beer. We'll talk about this.

Why does infection occur?

How to avoid infection when mashing.

This is perhaps the easiest part. During mashing, you gradually raise the temperature of the mash, and after 65 degrees, all the infection in the mash is already dying, so even if something got there, and it’s definitely something that got there with malt and water, nothing terrible will happen. A surprise can await you if, after mashing, you let the wort cool down. in a cold must, and especially at a temperature of 37 degrees, the infection can get there and breed there with great pleasure. Of course, when boiled, all this rubbish will die, but what it has managed to work out will remain in your beer ... It turns out that you put already sour beer on fermentation.

In order to avoid such situations, try to switch to boiling as soon as possible after mashing.

There are times when you need to let go. And the wort has time to cool down. How to be then? It's not all that scary either. Cover the wort with a lid while it is still hot. - it would be enough. In a hot wort, all the infection will die, and the lid will not allow a new one to enter. Such simple steps help you avoid contamination of the wort during the mashing and boiling stages.

How to avoid contamination of the wort during cooling.

From the moment you take the wort off the stove and set it to cool, the most risky period of time comes. During this period, any contagion, be it bacteria or wild yeast, can successfully spoil the taste of your beer. Avoiding contamination of the wort at this stage is not so difficult. The first thing to understand is that you need to prevent contact of the wort that has cooled below 60 degrees with open air. Dust that you simply cannot get rid of at home can carry a source of infection.

Which exit?

I just cool in a bath of water, someone uses a chiller. If you use, then just dip it into the pot with the wort 10-15 minutes before the end of the boil - let it boil. If you, like me, cool the wort in a bath of water, then cool it to 65 degrees, and then pour it into a fermenter.

By pouring still hot wort into the fermenter, you minimize the risk of infection during overflow. Plus, the hot wort will also kill bacteria and fungi that may be in the fermenter. Of course, you need to wash it. Plastic bottles normally survive this temperature .. although it all depends on the plastic.

How to prevent contamination of beer during fermentation.

Avoid spills. The more often green beer comes into contact with anything other than the fermentation tank, the more likely it is to become contaminated.

Wash the walker thoroughly with a brush and disinfectant (only non-chlorine)

Do not open the walker once again

How to avoid contamination of beer during bottling.

It's even easier here. Alcohol and hops in beer - will resist most infections, however, you should follow only 2 rules.

Decided to take another step forward home brewer. After all, as you know, the coolest home brewers are those who sternly brew beer only from self-grown barley malted on the balcony 🙂 . Well, jokes aside, I decided to try out a new (relatively) set for home brewing courtesy of the store pivovarnya.ru. The set is called Inpinto Craft Octoberfest Vienna. Includes: a jar of unhopped concentrate, two bags of pre-ground malt (Caramel and Vienna), a special bag for malt, two bags of hops (Select and Halertau), a Neodischer tablet for disinfecting equipment, S-33 yeast and instructions.

Why such half-hearted measures? Why not cook whole grains right away?

For many beginner homebrewers, the so-called “algrain” (malt-only brew, no concentrate) is a bit of a dread. What if it doesn't work?! How are you supposed to take any pauses? Oh, how difficult! Probably, such sets are produced to overcome such complexes. Even if you mess up something with malt brewing, you will always straighten it out with concentrate. Well, to show that there is nothing prohibitively complicated in "algraine". And so, let's go ...!

First, it's a saucepan. For concentrate brews, I quite managed a small home saucepan for 4 liters. More is needed here. Ten liters. I couldn’t find one in my kitchen, so I stole it from Zhenya Roshchin, the leader of home brewers and, fortunately, a neighbor in the district.

For those who intend to buy something like this, I’ll tell you right away - you don’t need to spend money on branded pans like Rondell, etc.. Leave this for the culinary specialists. Go to Ikea and buy an inexpensive Ikea. Here she is.

As you can see, I hung an electronic thermometer on it. Very comfortably. I set the desired temperature and when it was reached, the thermometer signaled. I don’t know where these are sold, this one came with an oven, but there is probably something similar, and even more so, you can get by with a simple electronic thermometer.

The instructions recommended mashing the malt at a temperature of 65-75 ° C for thirty minutes. I decided to keep the temperature at 65-66 ° C, in the last 10 minutes raise it to 73-74 ° C and cook not thirty, but forty minutes. This is the only change I made to the recipe.

He poured the malt into a bag and lowered it into heated water.

Maintaining a given range was not difficult. Having caught up with the temperature to 66, from time to time I either increased or decreased the temperature. On my stove, it was on notches 2-3. At the same time, the wort was stirred for uniform heating. If this is not done, then the temperature in different parts differed by almost ten degrees.

While the malt was mashing, I spread the yeast. Probably you can not do it, and as the manufacturers write, pour the dry ones directly into the chilled wort. But I prefer to breed. So at least you can see when the yeast is dead and avoid using them.

All. The mashing is over and you need to get the magic bag. There is still a lot of liquid in it and there is absolutely no need to lose the wort. The instruction recommends letting it drain. In the kitchen arsenal, a special pizza pan with holes was found. I used it (of course, you can take any colander), plus I rolled a rolling pin over the bag for better wringing.

The end result is a light brown wort.

We add concentrate to it, preheating the jar under hot water, for ease of extraction from the container.

The wort acquires a more saturated color.

We bring it to 100 ºС and, in accordance with the brewing map (included in the instructions), we add hops. First one - boil for forty minutes, then the other - boil for twenty minutes.

Thus, total time boiling was an hour. During boiling, not only are the aromatic and bitter components of the hops extracted, but the proteins contained in the wort coagulate, floating to the surface in the form of foam (as when boiling meat broth).

After boiling, I removed it with a regular slotted spoon.

As a result, we get somewhere around three or four liters of wort (part of it has boiled away).

Dilute with hot water (not only beer giants use highgravity 🙂) to the required volume.

Then the hot wort must be cooled and the sooner the better. The shorter the cooling time, the less likely it is that some rubbish will get into the warm wort, which can hide and cause us a lot of trouble in the future. Ideally, it would be nice to have a coil from copper tube immersed in a saucepan and connected to a faucet with cold water. Alas, I do not have such a device. I do it easier. I pour the hot wort into a barrel and put it on the balcony. Thus, it is guaranteed that there will be no extraneous microflora in the barrel (the wort is hot).

Alas, it's not winter anymore and wait for cooling until desired temperature(25-26 ºC) took a long time (three hours). Yeast was able to bring in only at two in the morning.

Measurement of the original density. Important point. To measure with a hydrometer, the temperature of the wort must be 20 ºC (if more, you can use conversion tables or special programs), and 200 milliliters are required, which is a bit much for a total volume of 9 liters. To avoid this trouble, on the advice of friends, I bought a refractometer. Some say that it does not determine the value very correctly, but I do not think that it is lying much and that this is critical for homebrew.

According to my measurements, exactly 16% density was obtained.

That's it, now we set the yeast and put the keg in the corner for at least a week.

General impressions - there is nothing complicated in grain cooking. Maintaining the set temperature within +/- 1-2 ºC is not difficult. In the future, I plan to use these nylon bags for brewing whole grain beers. For such a volume, it is more convenient than fooling around with filtration.

Thanks to Pivovarna.ru for the provided kits. There is still a set of Craft Imperial Stout left in the stash.