The chemical composition of beer foam is mainly protein decomposition products and glucose polymers and isohumulones, among which protein factors are the most important. Beer foam is one of the distinguishing marks from other beverages, and it is also an important quality indicator. The quality beer bubbles are white and delicate, uniform in size, lasting cups, creamy, and pleasing and refreshing. "Liquid bread" in the world. Beer foam appearance, foaming ability, persistence, adhesion is the four important aspects of beer foam performance, they are interrelated, this paper will be from its composition and improvement measures in the production process to talk about beer bubble.

First, the main constituent of beer foam

1, Protein: protein Longding distinction between the A distinction and B distinction between the protein is one of the main material of beer foam, especially in the B distinction between the nitrogen material is the formation of a good bubble of the basic material. These proteins can form a layer of adhesive, flexible and airtight protein bubble film.

Polypeptides are in the form of glycoproteins that affect the foam, they have a surface active effect, increasing the viscosity of the bubble and reducing the rate at which the vacancy is falling into the liquid. And the sugar in the glycoprotein protects the polypeptide from the precipitation loss during the brewing process. The greater the hydrophobicity of the polypeptide, the more stable the formation of the foam, and the greater the hydrophobicity of the polypeptide molecules in the same range, the greater the stability of the foam.

2, Isohumulone: it is the hops in the humplings in the wort when the formation of isomerization, it can improve the foam of the cup. Studies have shown that with a certain negative charge of isohumulones can be positively charged with peptide binding to the ion bond, the complex is the main body of beer foam.

3, CO2: beer foam is actually its own contained in the release of CO2 gas containing protein and other colloidal solution formed in the dispersion. Subtle bubbles make the beer have a certain thick, delicate and soft, improve the dispersion and flavor. CO2 content not only affects the release rate of surface gases, but also affects the size of the foam and the foam density. It is generally considered that the foam with a diameter of 0.2 mm is optimal.

Second, the formation of beer foam elements

1, Surface active substances: protein, hops resin and other surface active substances, so that the beer has a low surface tension, promote the formation of the bubble. And a flexible protective layer is formed between the bubbles to prevent the aggregation of the bubbles from being conducive to the durability of the foam.

2, Metal ions: nickel and other metal ions with beer can be combined with α-acid into insoluble substances, thereby enhancing the foam stability and adhesion. But the metal ions on the beer colloid and flavor stability of the impact of the production process need to pay attention to control.

3, Alcohol: alcohol can dissolve many water-soluble substances and non-polar solvent dissolved substances, such as hops resin. Alcohol can also be combined with CO2, peptides, etc., and weaken the surface tension. Therefore, the amount of alcohol is conducive to enhance the beer surface viscosity.

4, Beer viscosity: protein and wheat gel material with high viscosity, easy to form a greater strength of the boundaries of the film so that the formation of the bubble is not easy to disappear, conducive to the bubble lasting.

5, Temperature and PH: These are related to the release of CO2 and the isoelectric point of the protein, when the temperature and pH are low, the foam is more durable.

Third, the role of beer in the foam resistance

1, Fatty acids: beer in the fatty acids are mainly derived from raw materials and fermentation and storage of yeast yeast secretions. In the absence of bubble protein, their impact is greater, but also makes the foam rough. Among them, unsaturated fatty acids have a great influence on the performance of beer foam. So when drinking beer, if the cup is unclean with grease, even after the high-quality beer into the bubble is very poor.

2, Yeast autolytic material: yeast autolysis will release a large number of free fatty acids, the release of proteolytic enzymes will be hydrolysis of beer in the bubble protein. But also the precipitation of alkaline amino acids, these substances into the beer, the bubble will have a negative impact.

3, Higher alcohols: fermentation will produce a certain amount of higher alcohols, higher alcohols have a strong defoaming effect, so need to control the higher alcohol content.

Fourth, to improve and improve the performance of beer foam measures

1, Raw and auxiliary materials

1) Malt: the use of protein content of 9 to 12% of the malt is better, because of its high molecular protein decomposition products conducive to foaming characteristics, but also to increase the probability of beer turbidity. The use of the library value of 39 to 42% of the malt, to ensure that the distinction between the wort in the A, B distinction were about 20%, 15 to 20%.

2) Yeast: choose to secrete honey disaccharidase and proteolytic enzymes less, good cohesion, metabolic byproducts constitute a reasonable species. Production as far as possible the use of short storage time fresh, fermentation capacity and vitality, algebra low yeast.

3) Brewing water: the higher the residual alkalinity of the water, the greater the impact of carbonate hardness, PH value is higher, is not conducive to access to polymer protein, a greater impact on the bubble. In addition, the metal ion content in the water also requires control, such as iron, nickel and other ions.

4) Hops: Use fresh, high-quality hops to provide certain molybdenum, the best α-acid composition and the lowest content of fatty acids. Hops must be stored under low temperature and oxygen conditions to prevent α-acid oxidation and free fatty acid increase.

5) Auxiliary raw materials: common accessories are rice, corn, barley, wheat, which wheat glycoprotein content is high, so add some wheat or wheat flour as an auxiliary material is conducive to enhancing the beer foam performance. Rice and corn starch contains a certain amount of fat, destruction of beer foam.

2, Saccharification process

1) Temperature has a great effect on protein decomposition. On the well-dissolved malt, saccharification pot can be 52 ~ 55 ℃ under the material, and 30 to 40 minutes to stop, to improve the high molecular weight, the formation of foam protein, gelatin andviscous substances. But must ensure that the amount of α-N, especially for the poor malt.

2) High concentration of saccharification mash, low PH conditions, the enzyme activity is stable, is conducive to the decomposition of protein, and get a relatively high polymer nitrogen.

3) Saccharification process, but also to maintain the right amount of β-glucan, it is also a material that constitutes a bubble.

4) Filter tank filter wort must be clear, control the water temperature is 75 ~ 76 ℃, pH 5.8 ~ 6.0, is strictly prohibited to wash too much, otherwise it will make a lot of polyphenols, fatty acids into wort, is not conducive to Beer bubble.

5) When the wort is boiled, add a certain amount of granule hops or hops to extract about 20ppm of isohumulone by boiling to directly improve the foam properties. The amount of hops added is reasonable because the concentration of isohumulones is slightly reduced as it is added. The longer the boiling time, the higher the yield of the isohumulone, but the slower the rate of agglomerate nitrogen, the increase in the volatilization of the sesame oil, and the poor nature of the melanin stabilized foam. But against the bubble, energy consumption is also high

6) Wort cooling in the rotary sedimentation tank before there should be sufficient clarification time, to facilitate the full removal of hot coagulation, so that condensate fatty acids dispersed in the fermentation broth, or even into the beer, resulting in poor beer bubble.

7) The use of the bottom of the pump mash, adjust the mixer speed, etc., to avoid mash and wort oxidation, to retain a certain amount of polyphenols, is conducive to beer foam.

3, Fermentation process: the fermentation stage of the formation of beer foam is very important, different fermentation conditions must form a different quality of the bubble, we must control the yeast factor and fermentation process.

1) Cold wort oxygen content of 8 ~ 10ppm, to reduce the loss of foam in the pipeline.

2) fermentation temperature is too high, is not conducive to the bubble. Because the fermentation temperature is high, fermented fermentation, will lead to higher alcohols and other fermentation byproducts and CO2 release quickly increase the loss of foam material. Fermentation can maintain a certain pressure of the fermentation tank, while trying to avoid the process of oxygen, which will help control the amount of by-products.

3) Late fermentation should not be too radical, otherwise it will stimulate the yeast secretion of protease.

4) The content of α-N in cold wort was sufficient, the inoculation amount of yeast was 12 ~ 15 × 106 / ml, the inoculation temperature should not be high, and the settling yeast was separated as soon as possible.

5) To develop condensate, yeast emissions system, the provisions of time and emissions.

6) The end of the fermentation at -1 ~ 0 ℃ for about a week, not too long, while maintaining a constant pressure of about 0.08MPa, making CO2 fully saturated and with some of the ingredients of beer, beer foam and colloidal stability are favorable.

4, Sake filter process

1) Strict control of diatomaceous earth, silica gel and other treatment agent dosage and filtration accuracy, otherwise it will make part of the foam material loss.

2) The use of CO2 tanker pressure, to ensure that the amount of water CO2.

3) Add the appropriate amount of foam stabilizer and tetrahydro isomer hops extract and other hops products, easy to improve the foam performance, to prevent the production of sunny material.

4) The end of the wine at 0 ~ 4℃ storage 6 to 8 hours, conducive to water, alcohol and CO2, such as the combination and full dissolution.

5, Filling process

1) Glass bottles in the production of raw materials can not have alkali and defoamers and other substances free.

2) The end of the bottle can not have cleaning agents and oil residues, especially in the cleaning agent in the surfactant and defoamer.

3) Filling machine wine valve, wine tube, wine tank and other parts can not be cleaned after oil and other residues.

4) Filling, keep the sake of constant low temperature filling, pressure appropriate and stable, especially for the sake of wine cans or varieties, should try to avoid the loss of CO2, foam material and froth.

6, Other

1) The production process, wort, fermentation broth and sake transport to be smooth, to avoid the vortex and blister, to prevent the stability of the material loss of foam.

2) All equipment, pipes and other seals intact, in strict accordance with the provisions of health management and cleaning, to prevent oil and other substances into the gas and wine.

In short, the beer's foam performance is only one aspect of the quality of beer, it with beer colloidal stability, flavor stability may have a contradictory relationship. Therefore, beer producers, only take into account all aspects of the use of high-quality raw materials and advanced technical measures to develop a reasonable process, in order to produce high-quality beer.