Beer foam, commonly known as beer flower, is an important sensory indicator for evaluating beer. White, delicate, rich and stable beer foam can bring consumers fresh and refreshing visual enjoyment and tactile enjoyment for lips and mouth, arousing consumers' desire to taste. With the continuous understanding of consumers' knowledge of beer, higher requirements are put forward for the quality of beer. As an important quality index of beer, foam has participated in the market competition, and at the same time, it has been paid more and more attention by consumers. The quality of foam plays an important role in beer production.
1. Composition of beer
Beer is composed of protein and its decomposition products, minerals, vitamins, etc. These substances form the body of beer and form the unique flavor of beer, and protein plays an important role in the foam performance of beer. The main components of foam come from the "foaming protein" in malt and isohumulone in hops. It is a compound formed by combining the amino group of lysine and the hydroxyl group of isohumulone in "foaming protein". It has the hydrophilicity of protein and the hydrophobicity of isohumulones, thus forming good foam performance, durability and adhesion. The good foam performance of beer can only be guaranteed by perfect production technology.
2. The foam properties of beer include foaming ability, foaming appearance, foam persistence and foam endurance, etc.
1. The foaming performance of beer refers to the ability to form foam and the height of foam. When the beer is poured into the glass, there should be 1/3-1/2 foam in the upper part of the wine liquid, and the foam should be white and delicate at this time.
2. Foam persistence refers to the foam stability, which refers to the duration from the time the foam is formed to the time when the foam disappears. Good beer foam does not disappear completely after drinking beer.
3. The adhesion of foam is also called beer glass hanging property. For excellent beer, after drinking, the inner wall of the empty wine glass should be evenly covered with residual foam. The more residual foam, the better the foam adhesion.
3. Composition of beer foam
Beer foam is mainly a complex composed of carbon dioxide, foaming protein and isohumulone. It is composed of protein decomposition products, hop bitter substances, a small amount of lipids, metal ions and charged polysaccharides, among which the most important is foam protein.
4. Factors Affecting Beer Foam
1. The C02 content is insufficient, generally lower than 0.2%, or the foaming performance is poor because the gland is not tight and air leakage results.
2. An oil-lubricated air compressor is used, and the necessary air filtration and gas-liquid (oil) separation are not performed.
3. The proportion of protein composition in beer is not good, low viscosity, high surface tension and other reasons are not conducive to the formation and persistence of foam.
5. Measures to improve the performance of beer foam
1. The solubility of malt should be appropriate. Excessively dissolved malt will cause excessive protein decomposition, and the relative reduction of high and medium molecular nitrogen will reduce the role of protein as a natural foam stabilizer.
2. Use some cereal auxiliary materials, especially wheat as auxiliary raw materials, to increase foam performance. Because the glycoprotein contained in wheat is relatively high, it is particularly significant for improving foam performance.
3. Properly control the decomposition temperature of protein during saccharification according to the degree of malt decomposition. For well-dissolved malt, the protein decomposition temperature should be controlled at about 55°C, or even cancel the protein decomposition stage, so as to increase the protein content of high and medium molecules, which is beneficial to foam.
4. Properly adjust the pH value of wheat mash and wort. The pH value of wheat mash is controlled at about 5.6, and the pH value of wort is controlled at about 5.2, which is beneficial to foam.
5. The wort filtration should be clear, and the washing of the grains should be done properly, so as not to bring a lot of fatty acids into the wort, which will affect the foam performance.
6. Boiling wort with hops can improve the beer's foam retention and endow the foam with glass-hanging properties, which is mainly due to the effect of iso-a-acid. Although the wine without hops can form a good bubble retention, it does not hang the glass. High hop dosage and moderate wort boil time (1.5-2.0 hours) are good for foam.
7. The maturation time of beer should not be too long, otherwise the yeast will secrete too much protein, which will also affect the foam performance. Yeast autolysis should be prevented to prevent a large amount of protein from being released into the beer and affecting the foam.
8. Maintain proper wine storage time to saturate the carbon dioxide in the wine.
9. In every link of the brewing process, oily substances should be prevented from mixing into wort or beer.
10. The temperature of the fermented liquor should not be over-cooled, so as not to stimulate the yeast to secrete a large amount of protein and affect the foam.
In short, on the basis of not affecting the quality of beer taste, shelf life and other important quality indicators, certain technological measures should be taken. Improve the composition of beer related to foam performance, including increasing peptides, glycoproteins, and components related to increasing viscosity to reduce the surface tension of beer and increase the amount of foam stabilizing substances, the foam retention of beer can be improved.