Why does white foam form when brewing tea? Good tea foams when brewed
I microwave water to make tea. After it warmed up in the microwave and I dropped a tea bag (green tea) into the water, a thick white foam formed on top.
What is it and should I be concerned about drinking it?
Cascabel ♦
Without seeing it myself, I wonder: is there anything unique about your situation? Perhaps something about tea, water, or how you cleaned the cup?
fire.eagle
1, I also thought about it, although I do not get foam. However, when I pour in a Stash green tea bag, I get a flurry of white bubbles that bubble up to the surface, which doesn't happen when I use English breakfast mix, for example.
ashes999
Can you get a picture of this for us?
Answers
ElendilThe Tall
When you boil water in a cup in the microwave, it often boils without bubbles because unlike a kettle with a rough heating element or interior surface, a clean ceramic cup has little nucleation points. The nucleation points allow the formation of gas pockets, which turn into bubbles when water boils.
When you add a tea bag to hot water, you are essentially introducing thousands of nucleation points very quickly, and a lot of bubbles form very quickly - your foam. You must be careful when heating water this way before adding the tea bag, as if you heat it too long it can overheat and boil out of the mug when you add the tea bag.
Cascabel ♦
But why "thick white foam"? Bubbly/boiling water will usually form bubbles that disappear quickly, which can be described as thin and mostly clear rather than thick and white.
ElendilThe Tall
Foam in the eye of the beholder
jrounsav
When I leave the tea bag, thin transparent bubbles appear. A thick foam appears when I pour a tea bag into water. Perhaps the mixing action creates a thicker foam. Thank you Elendil!
Umbranus
For the reason Elendil points out, it is recommended to put a spoon in a cup of water when heated in the microwave. In this way, bubbles are formed in the air, preventing this overheating, also called boiling retardation. As long as the cup is non-conductive, a metal spoon will not cause harm in the microwave.
Lisa at Teasenz.com
There is nothing to worry about when you see foam appear. When hot water comes into contact with the tea, it extracts the amino acids and proteins that result in such foam.
The reason you get more foam on the surface is because when you use the microwave, the water is possibly submerging the bag in the hot water. When you first put the tea bag into the cup, some of the bubbles that appear are dissolved due to the moving water. Try to see if it matters.
Check this page for more information: https://www.teasenz.com/chinese-tea/foam-surface-tea.html
MandoMando
This may not be a direct answer to your question about what the foam is made of. But when does it form and how to avoid it.
This often happens if the water is not warm enough.
If you want to avoid this, you can try these steps:
Most tea leaves should be placed in water near the boiling point. It is 95C (or 200F) for black tea and 90C for green tea. If you're not at altitude, just make sure the water reaches the boiling point.
Pour boiling water over the tea bag already placed in the cup. Submerging a dry tea bag in hot water can lead to the problem ElendilTheTall talks about, as well as foam.
When buying food, each of us may encounter low-quality goods. Due to the negligence of the manufacturer, violation of technological standards, such a product is considered a defect and should be disposed of. But as often happens, the manufacturer does not want to lose money, and such a product ends up on store shelves. And if unscrupulous businessmen are engaged in the production of any food product, then there is no need to talk about the quality of the product. GlavRecept.Ru will help to distinguish high-quality sugar from a fake.
One of the most common food products - sugar, can also be of poor quality. Surely each of us at least once noticed that when sugar is added to tea, white foam appears on the surface of the liquid. Why this happens, we will try to figure it out.
Sugar is obtained from sugar cane or sugar beets. Moreover, cane sugar is the most ancient product. Mankind has been extracting sugar from cane for 24 centuries. Sugar from beets began to be made relatively recently, under Peter I. During the entire existence of sugar production, production technologies have not changed significantly.
Beetroot, which enters the sugar factories, is washed and poured with a solution of lime. This is done in order to disinfect beaten, cracked, rotten beets. Lime solution or lime "milk" destroys microbes and bacteria. If the manufacturer does not comply with the technology, lime residues end up in the finished product. And when such sugar is added to tea, a white foam appears on the surface of the liquid.
The next step in the production of sugar is the grinding of beets, obtaining the so-called shavings, from which sugar is extracted when water is added. Sugar is extracted from beets using special chemical compounds. They are called surfactants (surfactants). Basically, it's a cleanser. It turns out that surfactants are found in soap and washing powders. It has been observed that if surfactants similar to the surfactants of washing powder are added to a mixture of grated beets and water, the yield of sugar at the end of the process increases. Why is this happening? Roughly speaking, the beet chips were washed off. Surfactants stick together all the dirt in the sugar syrup and turn it into a precipitate. After that, the surfactants are filtered out. If this is done in violation of technology, surfactants get into the finished product. And this is definitely a marriage.
By themselves, surfactants in small doses are harmless. They pose a danger to the environment. Getting into sewage, and then into reservoirs, they accumulate. This slows down the growth of microflora.
How to distinguish high-quality sugar from a fake? The packaging must necessarily indicate the manufacturer, the date of manufacture or packaging, as well as the batch number. Even if you purchased a low-quality product, you are required to replace the product according to these details.
Sometimes in stores you can find sugar marked "sweet". Know. This is not natural sugar. And it's named sweet because it's sugar that has sweeteners added to it to triple the sweetness of the sugar.
Sugar quickly absorbs moisture. To make sure that the sugar has not become damp, twist the package in your hands. If it spills easily, it is dry. If the grains of sand stick to each other, the sugar was stored in a humid room. This is usually done by sellers who sell sugar by weight to give it weight.
Sugar is great at absorbing odors. Therefore, it must be stored separately from other products. To determine the sugar that has been saturated with foreign odors, you should hold a pinch of sugar in your hand and hold for a couple of minutes. After that, you need to smell the sugar. An unpleasant odor is a sign that the sugar has had time to smell.
To be sure of the quality of sugar, it must be dissolved in hot water. If it becomes cloudy and smells bad, there are impurities in the sugar.
Many nutritionists advise limiting sugar intake and replacing it with natural honey and natural fruits. Only in this case, your body will receive the necessary minerals and trace elements.
Writes Denis Shumakov, 2012-03-25
Yame Fukamushi Sencha Tokujo. Dry brew. Pictures for distribution.
Responsible Denis Shumakov, 2012-03-25
Yame Fukamushi Sencha Tokujo. Foam of the first infusion.
Responsible Denis Shumakov, 2012-03-25
Yame Fukamushi Sencha Tokujo. Foam of the second infusion.
Responsible Denis Shumakov, 2012-03-25
Yame Fukamushi Sencha Tokujo. Foam of the third infusion.
Responsible Denis Shumakov, 2012-03-25
Yame Fukamushi Sencha Tokujo. Infusion
Responsible Denis Shumakov, 2012-03-25
Yame Fukamushi Sencha Tokujo. Infusion in different dishes.
Responsible Denis Shumakov, 2012-03-25
Yame Fukamushi Sencha Tokujo. Sleepy and slippery sheet
Responsible listupal, 2012-03-25
I have long wanted to ask if tea foams is an indicator of what?
Surprisingly, he also paid attention to this. When a few years ago I was just starting to get acquainted with tea and studied Denis's mailing list, this phenomenon was noted there as a good sign - i.e. everything is done correctly, the water is soft, the temperature is right, etc. And I couldn't do it. Then he somehow raised the kettle higher so that the water fell, and bubbles climbed - as many as you like :) I also noticed that the shape of the kettle spout (which is filled with water) affects. You don’t pour out of a wide one so that it foams. But with a small hole, no effort is needed.
Responsible Xell, 2012-03-27
In fact, for the first time I hear about foam as a good sign. Maybe the methods are different, but at least in the southern part of Japan, water is poured carefully, no foam appears. Due to the way they are processed, even the best grades will have quite a large number of small particles, Japanese teapots make just counting on this, a fine mesh or a ceramic filter with a large number of small holes. And of course suitable sizes and shapes, 250-300ml for 2-3 people and 100-150ml for one.
Responsible Denis Shumakov, 2012-03-27
My tea foams almost always, Japanese tea is especially strong, and its foam is clearly different from pure bubbling.
I really like it - but this is, of course, a subjective criterion.
Is there some kind of physics? There is a lot of oxygen in the water or the particles are small. Bubbles form around something.
Responsible fggreg, 2012-03-28
Kst. there are studies on the study of tea foam. If I find it I'll post it. In short, froth formation is influenced by carbonates, and mainly calcium carbonates. And so does oxygen. Under nitrogen, tea foam does not form, and no foam is formed if the carbonates are quenched with acid (eg, add a few drops of lemon juice).
And the contained saponins in tea are also capable of foaming in an aqueous solution (“soaping”).
Some plants with a high content of saponins seem to be even used for washing, if I'm not mistaken =)
Responsible listupal, 2012-03-28
Usually the Wishans indulge in foaming) It was the case that the bubble remained at the bottom of the bowl, somewhere there is a photo. I'll post it if I find it, but how do the flower-fruit bowls smell after brewing)). So I'm thinking of getting a special teapot and "tarring" it with oolongs.
Max, thanks for the link. The author asked a question there, but he himself does not know the exact answer. He says that once at a time it doesn’t have to - even the same tea on different days sometimes foams, then it doesn’t foam. He googled, and this is what he found (among the alleged causes of foaming):
- remaining detergent on the dishes;
- the ingress of oxygen into the water during the spill shakes up (or excites) tannic acid (?);
- mixing cold and hot water;
- dissolved solids in water;
- boiling water scalds the leaves;
- very small particles on tea leaves and other impurities float on the surface and collect foam;
- water heated in a microwave oven causes foam;
- foam is denatured proteins separated from the leaves;
according to prof. Ermolaeva - bubbles are gases and it is not necessary that these gases come out of the water when boiling, because it is they who are involved in "fishing out" all sorts of tasty things from the leaf. That is why boiled water from a coffee machine kills every taste and aroma.
Responsible Xell, 2012-03-28
At least foam is not a direct indicator of quality, i. if there is no foam, this does not mean that the tea is bad :) The main thing is to drink the tea that you like and drink as you like.
I heard different opinions about boiling water, mostly they say that it is better to immediately remove from heat as soon as bubbles begin to appear. According to my personal experience, bringing to a boil is not necessary and it can slightly improve the taste of tea. Previously, there were no accurate measuring instruments, so boiling water was the starting point, how many times and where to pour. Tea masters achieve accurate temperature without thermometers. They also boiled water to kill dangerous animals. Nowadays, there are thermometers and accurate scales, water is safe in most places (especially if you use bottled water), in general, brewing tea has become extremely simple.
Responsible fggreg, 2012-03-28
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Victor Ermolaev
bubbles are gases and it is not necessary that these gases come out of the water when boiling
\
In any case, all gases will come out when boiling (to boiling) water, if you do not use an autoclave. And given the incredibly low concentration of oxygen, nitrogen, and other gases in water, when boiling, it is still mostly water vapor in the bubbles. At 100°C, O2 is almost absent in water, and at 80°C, only ~3 mg per 1 liter (need to be rechecked). This is very little. Inert gases do not count. As the water cools, it re-saturates with O2.
Polyphenols are also able to more or less easily absorb O2 from the air in an aqueous solution (or rather, quickly bind the newly absorbed O2 with water), while oxidizing themselves, and complementing the taste. Those. it turns out that the presence of the most dissolved O2 in water does not matter. (?)
Article on the study of "tea foam":
Kinetics and equilibria of tea infusion.Part 11 The kinetics of the formation of tea scum
M. Spiro; D. Jaganyi, Food Chemistry, 1994, 49 (4), pp. 359–365
http://rghost.ru/...
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Ronnie
Is there some kind of physics? There is a lot of oxygen in the water or the particles are small. Bubbles form around something.
\
Work on the composition and structure of "tea foam":
Kinetics and equilibria of tea infusion. Part 10. The composition and structure of tea scum.
Michael Spiro & Deogratius Jaganyi, Food Chemistry 1994, 49 (4), pp. 351-357
http://rghost.ru/...
this foam is not so simple =) In general, Michael Spiro has a lot of work on tea.
Responsible Xell, 2012-03-28
M. Spiro writes about the film that appears in black tea over time, as far as I understand. And not the foam that we see here in the photographs. True, I just flipped through, as I wake up I read. Such texts are somehow not read at night :)
Responsible fggreg, 2012-03-29
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Xell
And not the foam that we see here in the photographs.
\
Abundant foam that in the pictures above is quite possibly additional due to the presence of a large amount of saponins. The truth of the work on the effect of tea saponins on the formation of foam has not yet been found. But "all" saponins in an aqueous solution more or less foam (like soap).
Responsible Denis Shumakov, 2012-03-29
By the way, sleeping Japanese tea is very soapy to the touch. Could it be saponins too?
Responsible Veta, 2012-03-29
Dear forum users, I want to draw your attention to the material published on the Puer.ru forum.
http://www.puer.ru/...
Theme: Art of tea No5. Overview of gelatin in tea
Geng Jianxing and Zhang Yanren
Overview of Gelatin Characteristics of Tea
Quotes:
"...if a certain tea contains a high amount of gelatinous substance, then it is most likely to give a sensation of viscosity.
This gelatinous content visually resembles a sticky, gelatinous substance...."
"...This substance can be more accurately recognized through the manifestation of saponin in the tea solution. Saponin refers to the subtle pure white foam-like substance that occurs as soon as water is poured onto the tea leaves...."
"...To make it easier to see the saponin, we raise the teapot when pouring from it into the tea cup. The elongated jet of water agitates a large amount of saponin. When pouring is completed, you can notice the distribution of saponin on the surface of the tea. Based on repeated observations, we came to the following conclusions: the adhesive component is relatively liquid, such a saponin foam will be relatively fluid and easily dissolve (disappear). It will also easily flow from the edge If the glutinous content is high, the foam created by the saponin will be thick and may remain fixed on the surface of the tea in the center of the cup.
...."
Translation: Alexey Churakov
Editing: Denis Shumakov
Ahhh, so Denis knew something! Back in 2010!
Move away from the bubbles a little... Question to the leader: how did the Japanese teas arrive? Long gone? Were there any claims at customs? Is radioactivity normal? :)
Responsible Denis Shumakov, 2012-03-29
The teas went, according to my estimates, two or three weeks. I was in a frenzy, the parcel went to the address of my parents, so I didn’t cut off the exact dates. There were no problems with customs. But the parcel was small.
Quote
I knew but forgot. It happens to me all the time now.
End quotes
And I, Denis Aleksandrovich, even forgot what I was translating. Only when I saw the word saponin did the thought flash that I had already seen it somewhere.
Conclusion: I propose to tie: you - with the site "Sit, eat, drink", and we (in the sense of both) - with visits to the wine-growing regions of Europe.
Responsible Xell, 2012-03-29
There was an interesting question, now it has become more or less clear how the foam appears in tea.
Parcels reach Russia without problems, but with terms in different ways, EMS is about two weeks, Air Mail and SAL are lucky, from 2-3 weeks to 4-5. But lately it seems to be getting faster. There are no problems with radiation, because. plantations in Uji (Kyoto) and everything to the south did not hurt at all. There is still something left in Shizuoka, the infection rate has dropped ten times since last year. The Japanese also tightened the maximum content of radioactive particles in food to 100bq/kg that is allowed for consumption, which is 10 times lower than the international norm.
Responsible Denis Shumakov, 2012-03-29
I would quit. But I really like sherry. And I want to make a tea and sherry festival in Jerez. In ten years, when I become fat and famous.
Responsible Veta, 2012-03-29
Quote:
"Some plants with a high content of saponins, they even seem to be used for washing, if I'm not mistaken =)"
(c) fggreg, 2012-03-28
Some information about saponin.
(apparently, sleeping Japanese tea can wash things;))
From here: http://www.himiinet.ru/...
The following plants containing saponin are known: soap root, horse chestnut (fruit), soapwort, .... The soap root (the most common) contains about 30% saponin.
Saponins do not change the color of fabrics, do not cause shrinkage of wool, do not weaken fabrics, and silk does not lose its luster when washed with saponins. This is the advantage of saponin.
From here: http://www.treeland.ru/...
The powerful washing effect of the soap nut is achieved due to the substance - saponin, contained up to 38% in the shell.
Studies show that the saponin found in soap nuts inhibits the growth of tumor cells. Soap nut seeds are used in China in dentistry to prevent tooth decay.
From here: http://cellec.ru/...
The toxic effect of saponins on the human body depends on their nature. The most active (and at the same time the most poisonous) saponins are called sapotoxins. They are found in snake venom.
Saponins contained in plants are practically safe for humans - only their intravenous administration can affect health. In the form of dust, saponins act irritatingly on the mucous membranes of the respiratory organs, causing severe sneezing and a sensation of scratching in the throat. Saponins have a pungent, often pungent, bitter taste that lingers for a long time.
Responsible Veta, 2012-03-29
Quote
"The Japanese also tightened the maximum content of radioactive particles in food ..."
(c) Xell, 2012-03-28
I heard in the fall that, on the contrary, they increased the allowable rate of food radioactivity.
Responsible Xell
2 listupal, 2012-03-28
Usually the Wishans indulge in foaming) It was the case that the bubble remained at the bottom of the bowl, somewhere there is a photo. I'll post it if I find it, but how do the flower-fruit bowls smell after brewing)). So I'm thinking of getting a special teapot and "tarring" it with oolongs.
_____
By the way, sometimes luck smiles and good tea comes across, the teapot spout is next to the top of the cup, and half a centimeter foam around the circumference of the cup in diameter in the form of really intertwined pearls, as in the article, despite the fact that it remains at the bottom of the cup. There is a suspicion that this is an indicator of zheng yancha.
Experts advise paying attention to the appearance of the film. The uniform color of the plaque or the smallest inclusions in it indicate that the cause of the formation of the film was too hard tap water. The high content of calcium carbonate in water, when combined with organic substances contained in tea, causes the appearance of a film. If you add a slice of lemon or a drop of lemon juice to the drink, it will disappear.
There is also an opinion that the reason for the formation of the film is the oxidation of the iron contained in the water.
rainbow in a cup
A thin iridescent film, homogeneous and easily broken when the drink is stirred, is formed by essential oils and tannins contained in tea and giving it a unique aroma and tart taste. If the brewed tea stands untouched for some time, the oils and tannins are oxidized - the result of this oxidation is an iridescent film on the surface of the liquid. The stronger the tea, the more noticeable it will be.
Another appearance of a brownish film, according to experts, is the oxidation of mineral and organic compounds, including caffeine and catechins contained in tea, under the influence of oxygen in the air. The composition of this film is very complex - it includes compounds, purines, tannins, iron, calcium, and other substances and compounds.
Harmful or helpful?
Opinions of experts about the effect of tea with a film on differ. On the one hand, it is evidence of a high content of useful essential oils, on the other hand, it forms an insoluble plaque, which, with the constant use of strongly brewed tea, can settle on the mucous membrane of the stomach and intestines, preventing the absorption of nutrients.
It has been established that drinking tea that has stood for a long time has the worst effect on human health - after brewing, black tea should be drunk for several hours, in no case leaving the tea leaves overnight. After that, the drink loses its beneficial properties, it increases the content of harmful substances, including toxic guanidine, which is formed during the oxidation of non-hazardous guanine contained in tea.
High concentrations of guanidine are extremely dangerous, and for the onset of symptoms of poisoning, it is enough to drink a few cups of yesterday's strong brew.
Due to the film, a poorly washed off coating forms on the walls of the cups, which sometimes even washing in the dishwasher does not help to get rid of. If the tap water in your area contains a lot of calcium, magnesium and iron salts, it is better to get a special filter or use purified drinking water to make tea. Do not forget that distilled water, like too hard, does not bring any benefit to the body.
As the ancient Chinese proverb says, "Every cup of tea drunk ruins the pharmacist." The wisdom of the Chinese is echoed by the Russian proverb that, they say, "you drink tea - you will live up to a hundred years." And in fact, so much has already been written about the beneficial properties of both black and green teas. But as you know, any even the most super healthy and delicious food or drink, under certain conditions, can not only cease to be beneficial, but even harm.
Sometimes, having brewed a cup of fragrant hot tea, we notice with bewilderment a thin mother-of-pearl film on its surface. Most people immediately pour out such tea without even thinking about why the film forms on the tea. But aren't they making a mistake by acting so radically with the drink?
In fact, science cannot yet give an unambiguous answer to this question. There are at least two almost opposite opinions about the film on tea. In the first variant, the version is considered that the film on tea is formed due to the fault of low-quality hard water. This means that it is worth taking a more thoughtful approach to the choice of water for tea drinking - either install filters on the tap, or use additionally purified bottled water.
In an alternative version, we are talking about the fact that the film on tea is formed due to the components of the tea itself. Tea contains up to 300 different components, which, when mixed with water, form various compounds. But even in this version, opinions are divided. Some researchers say that such compounds of caffeine and catechins are very harmful, because they clog blood vessels and harm the liver, automatically turning healthy tea into a harmful liquid. Other researchers are of the opinion that this film is formed by essential oils contained in tea. Moreover, the higher the grade of tea and the better the processing of the tea leaf, the more essential oils it contains, and, therefore, such a film indicates that the tea you are brewing is of good grade.
But, despite such a lack of unity in the answers to the question “why does a film form on tea”, everyone agrees on one thing - it is useful to drink tea freshly brewed and you should not subject it to prolonged stagnation in a cup or teapot.
How to get rid of film on tea
Since the film on the tea is formed when it cools, you can simply add a little hot water. It also contributes to the destruction of the film, it is worth adding a slice of lemon if the iridescent overflows on the cooling tea confuse your aesthetic perception. And for lovers of cold tea, we can recommend its rapid cooling with ice cubes - this method allows you to get a cold drink and avoid the appearance of an embarrassing film.
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