About beer through the eyes of a chemist. Part 2

About beer through the eyes of a chemist. Part 2




Hi% username%.

If you have a question right now: “Hey, what does Part 2 mean - and where is the first ?!” - go urgently here .

Well, for those who are already familiar with the first part - go directly to the case.

Yes, and I know that for many people, Friday has just begun - well, that’s the reason to prepare for the evening.

Let's go.

At the very beginning I will tell you all the same about the difficult path of beer in Iceland.

Prohibition in Iceland came even earlier than in the United States - in 1915. However, the situation did not last long, because in response went hard, as they say, counter-sanctions: Spain, having lost the Icelandic market for wine, stopped in response to buy fish from Iceland. They managed to tolerate it for only six years, and since 1921 wine has been excluded from the list of prohibited foods in Iceland. Beer, however, no.

Another 14 years from persistent Icelanders took it to regain the right to drink spirits: in 1935 you could drink wine, rum, whiskey and everything else, but you could not drink beer any stronger than 2.25%. The leadership of the country then believed that normal beer contributes to the prosperity of depravity, because it is more accessible than strong alcohol (yes, of course).

The solution was found by the Icelanders quite simple and obvious, which even made me more attractive than after the European Championship in 2016: people just diluted the allowed beer with strong alcohol. Of course, the government always goes to meet its citizens, and that’s why in 1985 a convinced sober and ulcer the Minister of Human Rights (ironically!) Achieved a ban on this simple way.

The final use of beer in Iceland was allowed only on March 1, 1989, 74 years after the ban. And it is clear that ever since March 1 in Iceland is Beer Day: taverns work until the morning, and local people remember how three quarters of a century waited for the return of their favorite drink. You can, by the way, also add this date to your calendar when it’s right to miss a cup of foam.

In the next part, as an interesting story, I think I will write something about Guinness ...

But back to where you left off, namely the beer ingredients.

Malt


Malt is the second major component of beer after water. And not only beer - malt serves as the basis for the production of many fermented beverages - including kvass, kulagi, makhsim, and also whiskey. It is malt that is food for yeast, and therefore determines the strength, and some taste. Honey, granular, biscuit, nut, chocolate, coffee, caramel, bread - all these tastes do not appear due to chemistry (fortunately or unhappiness) - but due to malt. Moreover: no sane brewer will add anything extra that can be obtained that way. You'll see later that it's not just about the flavors you can get from malt.

Malt is a slightly germinated grass: barley, rye, wheat or oats. Barley malt is used always , if you drink wheat beer, then know that wheat malt in it is only an admixture to barley. Similarly, oat malt is an admixture of barley, it is used less often than wheat, but is used in the production of some stouts.

Malt is of two types: basic - gives the wort a lot of sugar for further fermentation, but does not affect the taste too much, and special - for the fermented sugar is poor, but it gives the beer a distinct taste. Much of the mass beers are produced using several basic malts.

Grain raw materials intended for brewing require pretreatment, which consists of turning it into brewing malt.The process involves the germination of cereal grains, drying and cleaning from sprouts. Extra malt processing can be done both at the brewery and at a separate enterprise (malting plant).

The process of obtaining malt is divided into soaking and germination of seeds. During germination, chemical reactions take place, new chemicals are formed. And the main role in this is played by various enzymes, which are numerous in germinating malt. Some we will now disassemble. Prepare yourself,% username%, now there will be a blow to the brain.

So, we have ready sprouted malt. Getting to mashing is the preparation of wort from malt. Malt is crushed, mixed with hot water, the mash (mixture of crushed grain products) gradually heats up. A gradual increase in temperature is necessary, because malt enzymes act differently at different temperatures. Temperature pauses affect the taste, strength, foaminess and density of a beer. And at different stages different enzymes are included.

Starch hydrolysis (amylolysis) during mashing catalyzes the amylose of the malt. In addition to these, malt contains several enzymes from the groups of amyloglucosidases and transferases, which attack some starch degradation products, however, in their quantitative ratio, they are only of secondary importance in mashing.

When mashing the natural substrate is starch contained in malt. Just like any natural starch, it is not a single chemical substance, but a mixture containing, depending on the origin, from 20 to 25% amylose and 75-80% amylopectin.

The amylose molecule forms long, unbranched, spiral-wound chains consisting of α-glucose molecules that are interconnected by glucosidic bonds at the α-1,4 position. The amount of glucose molecules varies and ranges from 60 to 600. Amylose is soluble in water and is fully hydrolyzed to maltose by the action of β-amylase of malt.

Amylopectin molecule consists of short branched chains. Along with bonds in the α-1,4 position, α-1.6 bonds are also found in branched places. Glucose units in the molecule, there are about 3,000 - amylopectin is much larger than amylose. Amylopectin without heating is insoluble in water, forms a paste when heated.

Malt contains two amylases. One of them catalyzes a reaction in which starch is rapidly broken down to dextrins, however, maltose forms relatively little — this amylase is called dextrinating or α-amylase (α-1,4-glucan-4-glucan hydrolase). Under the action of the second amylase, a large amount of maltose is formed - this is amylase saccharifying or β-amylase (β-1,4-glucan maltohydrolase).

Dextrin α-amylase is a typical malt component. α-Amylase is activated by malting. It catalyzes the cleavage of α-1,4 glucosidic bonds of the molecules of both components of starch, i.e. amylose and amylopectin, while only the final bonds are unevenly broken inside. There is a dilution and dextrinization, manifested in a rapid decrease in the viscosity of the solution (dilution of the mash). In natural environments, i.e., in malt extracts and congestion, α-amylase has a temperature optimum of 70 ° C and is inactivated at 80 ° C. The optimum pH zone is from 5 to 6 with a clear maximum on the pH curve. α-Amylase is very sensitive to hyperacidity (it is acid-resistant): it is inactivated by oxidation at pH 3 at 0 ° C or at pH 4.2-4.3 at 20 ° C.

Saccharifying β-amylase is contained in barley and its volume increases greatly during malting (germination). β-Amylase has a high ability to catalyze the breakdown of starch to maltose. It does not thin the insoluble native starch and even the starch paste. From the unbranched amylase chains, β-amylase cleaves the secondary α-1,4 glucosidic bonds, namely from the non-reducing (non-aldehyde) ends of the chains. Maltose gradually cleaves from individual chains of one molecule.The cleavage of amylopectin is the same, but the enzyme attacks the branched amylopectin molecule simultaneously in several spatial chains, namely in the branching sites where α-1.6 bonds are located, before which the splitting stops. The temperature optimum of β-amylase in malt extracts and congestion is at 60-65 ° C; it is inactivated at 75 ° C. The optimum pH zone is 4.5-5, according to other data - 4.65 at 40-50 ° C with a non-sharp maximum on the pH curve.

Totally, amylases are often called diastase, these enzymes are found in common malt types and in special diastatic malt, a natural mixture of α- and β-amylase, in which β-amylase quantitatively predominates over α-amylase. With the simultaneous action of both amylases, the hydrolysis of starch is much deeper than with the individual action of each one by one, and 75-80% is obtained from maltose.

The difference between the temperature optimum of α- and β-amylase in practice is used to adjust the interaction of both enzymes by supporting the activity of one enzyme to the detriment of the other by selecting the right temperature.

In addition to starch cleavage, protein cleavage is also extremely important. This process — proteolysis — catalyzes by mashing enzymes from the group of peptidases or proteinases (peptide hydrolases) that hydrolyze peptide bonds -CO-NH-. They are divided into endopeptidase, or proteinase (peptide peptidolidase) and exopeptidase or peptidase (dipeptide hydrolase). In jams, the substrates are residues of the proteinaceous matter of barley, i.e. leucosin, edestin, hordein and glutelin, partially altered during malting (for example, coagulated during drying) and their cleavage products, i.e. albumoses, peptones and polypeptides.

Barley and malt contain one enzyme from the group of endopeptidases (proteinases) and at least two exopeptidases (peptidases). Their hydrolyzing effect is complementary. By their properties, barley and malt proteinases belong to papain-type enzymes that are very common in plants. Their optimum temperature is between 50-60 ° C, the optimum pH ranges from 4.6 to 4.9, depending on the substrate. Protease is relatively stable at high temperatures and is thus different from peptidases. It is most stable in the isoelectric region, i.e., at a pH of 4.4 to 4.6. The activity of the enzyme in an aqueous medium decreases already after 1 h at 30 ° C; at 70 ° C after 1 h, it is completely destroyed.

The hydrolysis catalyzed by malt proteinase proceeds gradually. Several intermediate products were isolated between proteins and polypeptides, of which the most important are peptide fragments - peptones, also called proteoses, albuminosis, etc. These are the highest colloidal cleavage products that have typical protein properties. When boiling peptones do not coagulate. The solutions have an active surface, they are viscous and, when shaken, easily form a foam - this is extremely important in brewing!

The last degree of cleavage of proteins catalyzed by malt proteinase, are polypeptides. They are only partly high-molecular substances with colloidal properties. Normally, polypeptides form molecular solutions that diffuse easily. As a rule, they do not react as proteins and are not precipitated by tannin. Polypeptides are a peptidase substrate that complements the action of the protease.

The peptidase complex is represented in malt by two enzymes, but the presence of others is allowed. Peptidases catalyze the cleavage of terminal amino acid residues from peptides, with first forming dipeptides and, finally, amino acids. Peptidases are characterized by substrate specificity. Among them are both dipeptidases, hydrolyzing only dipeptides, and polypeptidases, which hydrolyze higher peptides containing at least three amino acids in a molecule. In the group of peptidases, aminopolypeptidases, whose activity causes the presence of a free amino group, and carboxypeptidases, which require the presence of a free carboxyl group, differ.All malt peptidases have an optimum pH in the weak alkaline region between pH 7 and 8 and an optimum temperature of about 40 ° C. At pH 6, at which proteolysis occurs in germinating barley, peptidase activity is pronounced, while at pH 4.5-5.0 (optimum proteinases) the peptidases are inactivated. In aqueous solutions, peptidase activity decreases already at 50 ° C, at 60 ° C peptidases are rapidly inactivated.

When mashing, great importance is attached to enzymes catalyzing the hydrolysis of phosphoric acid esters, as well as phospholipids of cell membranes. The removal of phosphoric acid is technically very important because of its direct effect on the acidity and the buffer system of brewing intermediates and beer, and fatty acids formed from phospholipids form esters during fermentation, causing various flavors. The natural substrate of malt phosphoesterases are esters of phosphoric acid, of which phytin predominates in malt. It is a mixture of calcium and magnesium salts of phytic acid, which is an inositol hexaphosphoric ester. In phosphatides, phosphorus is bound as an ester with glycerol, while nucleotides contain ribose phosphorus ester associated with a pyrimidine or purine base.

The most important malt phosphoesterase is phytase (mesoinose hexaphosphate phosphohydrolase). She is very active. Phytase gradually removes phosphoric acid from phytin. In doing so, various phosphorus esters of inositol are formed, which ultimately produce inositol and inorganic phosphate. Along with phytase, saccharophosphorylase, nucleotide pyrophosphatase, glycerophosphatase and pyrophosphatase have also been described. The optimum pH of malt phosphatases is in a relatively narrow range - from 5 to 5.5. They are sensitive to high temperatures in different ways. The optimal temperature range of 40-50 ° C is very close to the temperature range of peptidases (proteinases).

The formation of enzymes is strongly influenced by oxygen — when it is deficient, the grain simply does not germinate, and the light — it destroys some enzymes, in particular diastase, and therefore the malting rooms — they are arranged with a small amount of light.
Until the 19th century, it was believed that only such malt was suitable, the germination of which did not take place before the leaflet appeared. In the XIX century, it was proved that malt, in which the leaf reached a relatively large size (long malt, German Langmalz), contains significantly larger quantities of diastasis, if only the condition was at a possible low temperature.

Among other things, malt is also used for the preparation of the so-called malt extract. Malt extract is a wort condensed or evaporated by boiling from crushed barley grains, rye, corn, wheat, and other cereals. The wort is evaporated in a gentle manner under vacuum at a temperature of from 45 to 60 ° C until the consistency of the syrup is clarified, freed from astringent compounds by the method of separation and centrifugation. In the production of beer, malt extract is used quite rarely because it does not allow experimenting with a variety of taste and color.

A variety is very simple. Depending on the degree of drying, you can get malt of different types - light, dark, black. For dark and especially caramel varieties, the malt is roasted. The more malt is fried, the more sugars are caramelized in it. The caramel flavor gives the beer malt with actually the most real caramel inside: after steaming and drying, the starch contained in the malt turns into a caramelized hard mass. It is she who will bring the characteristic notes to the beer - and in the same way you can add a “burned taste” with the help of actually burnt burnt malt. And the Germans also have a “smoky beer” - rauhbir, in the preparation of which green malt smoked over the fire is used: the heat and smoke from burning fuel is dried and at the same time smoked sprouted grain.And the taste and aroma of the future beer is directly dependent on the fuel used to smoke the malt. In the Schlenkerla brewery (which, by the way, is already more than 600 years old), aged beech wood is used for these purposes, thanks to which this variety acquires a specific smoked profile - well, the attempts of these Bavarian brewers are clear: you need to look for some original options in a narrow framework German law on the purity of beer, however, we will talk about these and not only these “frameworks” after we have discussed all the ingredients of beer.

I must also say that it is impossible to brew beer from only dark varieties: during frying, the enzymes necessary for saccharification of the wort are lost. therefore, even the darkest rauchbir will contain light malt as well.

So, when using different types of malt, before the fermentation process, a whole range of different substances comes into the beer, the most important of which are:
  • Sugar (sucrose, glucose, maltose)
  • Amino acids and peptones
  • Fatty acids
  • Phosphoric acid ( Always Coca-Cola! Chur me, chur!)
  • Incomplete oxidation products when drying all of the above richness with a complex composition

With sugars everything is clear - this is future food for yeast, as well as the sweetish taste of beer (it was balanced before with herbs, and later with hops, adding bitterness), everything is clear and with products of incomplete burning it is a darker color, smoked and caramelized and smell. I said about the importance of peptones and foam - but I’m not tired of repeating it. We’ll come back to fatty acids when we talk about yeast and the appearance of fruit flavors.

By the way, speaking of peptones, proteins and cell death - I remembered something from one story, which I read on one of the thematic publics. She's under the spoiler for some reason.

Children, women and the faint of heart do not look!
For almost 10 years, one interesting Scottish brewery BrewDog has released an incredibly strong beer - as much 55%, which for a long time was the strongest beer in the world. So, a very small part of the batch of this drink was packed in protein (namely, bilocate, but not white) and other fur-bearing animals. A bottle of such a beer called The End of History (“The End of History”), in which the stuffed mammals were used in the design (they say carcasses were simply found on the roads), cost about $ 750.



We will end on this malt, mentioning only that domestic malt is not even very bad - and therefore it is actively used along with imported one.

Yeast


Another absolutely essential component of beer is, in fact, yeast. Well, where without them, right?

Brewer's yeast is a fermenting microorganism. Fermentation, in turn, is a biochemical process based on the redox transformations of organic compounds under anaerobic conditions, that is, without oxygen. During fermentation, the substrate - and in our case, sugar - is not fully oxidized, so fermentation is energy-inefficient. With different types of fermentation, the fermentation of one glucose molecule yields from 0.3 to 3.5 ATP molecules (adenosine triphosphate), while aerobic (i.e. oxygen consumption) respiration with complete oxidation of the substrate has an output of 38 ATP molecules. Due to the low energy yield, fermenting microorganisms are forced to recycle a huge amount of substrate.And this of course is good for us!

In addition to alcoholic fermentation, in which mono- and disaccharides are converted into ethanol and carbon dioxide, there is also lactic fermentation (the main result is lactic acid), propionic acid fermentation (result is lactic and acetic acid), formic fermentation (formic acid with variants), butyric acid fermentation (butyric and acetic acid) and homoacetate fermentation (only acetic acid). I must say that it is unlikely that a beer lover would want something other than a racially faithful alcoholic fermentation to occur - I don’t think anyone would want to drink a sour, smelling of rancid butter or missing cheese. That is why the share of “extraneous fermentation” is strongly controlled, in particular, by the purity of the yeast.

Yeast production is a huge industry: entire laboratories, independent or created at the brewery, are working on breeding strains of brewer's yeast with certain characteristics. The yeast recipe is often a secret, carefully guarded by the brewer. It is said that the peoples of northern Europe had a tradition to pass a special brewing stick from generation to generation. Without stirring the brew, this piece of beer did not work, so they considered the stick almost magic and kept it especially carefully. Of course, they did not know about yeast then and did not understand the true role of the stick, but already then they understood the value of this sacrament.

But on any rule there are exceptions. For example:

  • In Belgium Lambicas are brewed - this is a beer that starts to ferment on its own, thanks to microorganisms that get into the wort from the air. It is believed that real lambics can be obtained only in certain regions of Belgium, and it is clear that the fermentation there is so mixed and complex that the devil himself can break his leg. However, frankly: lambics - for an amateur, and certainly not suitable for those who believe that beer should not sour.
  • The American brewery Rogue Ales brewed ale at the base of the yeast, which the main brewer carefully grew in his own beard.
  • His Australian colleague from the 7 Cent brewery went even further and raised wild yeasts in his navel, and then released a beer based on them.
  • Polish brewery The Order of Yoni a few years ago brewed beer from women. Well, both from women ... from yeast from women. Women did not suffer at all ... Well, in short, you understand ...

In the process of fermentation, brewer's yeast not only eats sugar and produces what it should be, but also performs a large number of other chemical processes. In particular, the processes of esterification occur - the formation of esters: and what, alcohol, fatty acids (remember the malt?) - also, you can make a lot of interesting things from them! It can be a green apple (some American lagers have it), and a banana (typical of German wheat beer), and pear, and butter. But in reality, ethyl acetate, which is the most common (ethanol + acetic acid) would be in a high concentration, resembling the smell of nail polish, and in the concentration that is usually present in beer, it appears as a fruity aroma. Isoamyl acetate gives the drink a banana flavor. Ethylbutyrate - pineapple, ethylhexanoate - malic and anise notes. Here I recall a school and various ethers that smelled so that yum-yum-yum. But not all. Whether a drink with a fruit aroma or a subtle aroma of a mixture of sivukha and a solvent is obtained depends on the concentration of esters, which in turn depends on various factors: fermentation temperature, wort extractability, yeast strain, the amount of oxygen that has entered the wort. We will talk about this when we come to the consideration of brewing technology.

By the way, the yeast also affects the taste - we will remember this when we start talking about hops.

And now, since we met with yeast, we can report the only true way to divide beer.And no,% username%, it is not “light” and “dark”, because neither light nor dark does not exist, as 100% of blondes and 100% of brunettes do not exist. This is the division into ales and lagers.

Strictly speaking, fermentation in the eyes of the brewers is of two types: riding (yeast rises to the top of the wort) - this is how ale turns out, and grass roots (yeast goes to the bottom) - this is how lager is prepared. Easy to remember:

  • El - & gt; yeast roam high - & gt; fermentation temperature is high (approximately from +15 to +24 ° C) - & gt; consumption temperature is high (from +7 to +16 ° C).
  • Lager - & gt; yeast works low - & gt; fermentation temperature is low (approximately from +7 to +10 ° C) - & gt; consumption temperature is low (from +1 to +7 ° C).

El is the most ancient type of beer; it was the very first brewers who brewed it hundreds of years ago. Now most of the ales are characterized by: higher density, more complex taste, often fruit flavor and mostly darker (compared to lagers) color. An important advantage of ales is a relatively simple and cheap production that does not require additional refrigeration equipment, as is the case with lagers, and therefore all craft breweries can offer one or another ale.

Lager appeared later: its production began to be mastered more or less only in the 15th century, and only in the second half of the 19th century did it begin to gain serious momentum. Modern lagers are distinguished by a more comprehensible and often more hop flavor and aroma, as well as, as a rule, by a light color (although black lagers exist) and a lower strength value. The principal difference from ales: at the last stage of production, lagers are poured into special containers and matured there for several weeks or even months at temperatures close to zero — this process is called lagarization. Camp varieties are stored longer. Due to the ease of maintaining stable quality and long shelf life, lager is the most popular type of beer in the world: almost all large breweries produce lagers. However, since the production requires the complication of technology (remember the conversion), as well as the presence of special frost-resistant yeast - and therefore the presence of the original (namely, the original, and not re-branded) lagers in the list of the proposed varieties in any craft brewery is a sign of its status and experience. Brewers.

Many (including myself) believe that ales are a more “correct” beer compared to lagers. Ely are more complex in terms of flavors and tastes, they are often richer and more diverse. But lagers are easier to understand, they are often more refreshing and, on average, less strong. Lager differs from ale, including the fact that it lacks the obvious taste and aroma of yeast, which are important and sometimes obligatory for ales.

Well, that's figured out. Right? No, wrong - there are options when beer is a hybrid of lager and ale. For example, German Kölše is a top-fermented beer (i.e. ale) that ripens at low temperatures (like lager). As a result of such a hybrid production scheme, the drink has the characteristics of both types of beer: clarity, lightness and freshness side by side with barely noticeable fruit notes in the taste and short but pleasant sweetness. Well, a drop of hops in the end.

By the way, live for a century - learn: here’s a respected artoym told about Brett . Well, strictly speaking, these are not brewer's yeasts, but rather related microorganisms, as in Belgian lambics - but the information is interesting anyway.

In general, if you,% username%, suddenly felt that you began to understand the classification of beer, then here is your last:



To summarize the results of the yeast: the total is that the longer the yeast labors, the more the taste and character of the beer can change. This is especially true of ales, in which the concentration of substances affecting taste and aroma is higher. For this reason, some varieties of ales imply fermentation in the bottle: the beer is already poured into glass containers and stands on the shelf of the store, but fermentation is still taking place inside. Having bought a couple of bottles of such beer and having drunk them at different times, you can feel a significant difference. At the same time, pasteurization deprives the beer of certain taste characteristics, since it excludes the presence of live yeast in the drink. Actually, this is why many people value unfiltered beer: even after pasteurization, leftover yeast culture can make the drink tastier. The sediment that is visible on the bottom of the tank with unfiltered beer is what remains of yeast.

But all this will be after, but now we have to list a few more optional components of beer.

This is already in the next part.

Source text: About beer through the eyes of a chemist. Part 2