What is the relationship between protein rest and beer?

The control of the protein resting process is very important, so what does this have to do with the beer production process? What impact will the control of beer quality have?

What is Protein Rest Process?

In the saccharification process, the first stage after the malt feeding is the protein resting process. The time of this process can vary between 0 and 90 minutes. It decomposes the macromolecular proteins present in the malt to meet the needs of beer brewing and beer quality for medium and low molecular nitrogen content.

Impact on beer production process and quality

(1) Some brewers like to use a larger proportion of auxiliary materials, but the use of auxiliary materials reduces the level of total nitrogen and low molecular nitrogen in the wort. Therefore, in order to ensure the normal fermentation of the wort, protein rest must be carried out to obtain adequate nitrogen source.

(2) Since the protein decomposition level of barley raw materials can generally only reach 40% to 45% in the process of malting, and some malts are still lower than this level, in order to obtain enough different relatives that can meet the needs of fermentation. Molecular mass, nitrogen content of different levels, protein rest is required.

(3) Due to the needs of beer quality control, the content of high, medium and low molecular nitrogen should have a proportional level, which is different from the situation that malt simply requires the overall protein decomposition level to reach more than 40%. to meet this requirement.

(4) In the whole saccharification cycle, the length of protein rest time can vary greatly, because it is related to the quality of malt, the proportion of auxiliary materials, the concentration of wort and the variety of beer, etc. It is often adjusted, including pH, temperature and time, which is directly related to the control of the wort production process and the change of cycle time.

Relation to beer production process and quality control

(1) The quality of the control of the protein resting process is closely related to the proliferation of yeast and the prosperity of fermentation. If through effective control, the level of α-amino nitrogen in wort can meet the requirements of yeast reproduction, not only Good fermentation can be guaranteed, and the control of diacetyl is also extremely beneficial.

(2) Since the protein resting process is a low-temperature enzymatic decomposition process, low-temperature enzymes including glucanase, phosphatase, and phytase can also function effectively. Wort filtration and wort boiling play an important role. It can be said that, except for the case where no auxiliary materials are used and the quality of malt is very good, the protein resting process is an indispensable process in the wort manufacturing process. In this way, Its process control is also crucial.

(3) The effect of protein rest is closely related to the quality of beer, because the effective control of this process can adjust the ratio of high, medium and low relative molecular mass nitrogen in the wort, and this ratio should meet the 1:2.5:6.5 as much as possible. The basic requirements, that is to say, the content of high molecular nitrogen should be 10%~15%, the content of medium molecular nitrogen should be 20%~25%, and the content of low molecular nitrogen should be 60%~65%. Because high and medium molecular nitrogen plays an important role in the foam persistence and mellowness of beer, but macromolecular nitrogen has a certain influence on the abiotic stability of beer, so the amount of macromolecular nitrogen should not be too much; Low molecular nitrogen plays an extremely important role in the reproduction of yeast, and is an indispensable source of chlorine for the growth of yeast, but its quantity should not be too much, otherwise it will affect the taste and foam. This requirement can be met by controlling the temperature, pH, time, water ratio, raw material ratio and other aspects of the protein resting process.

(4) The protein resting process is also closely related to the flavor of beer, because low molecular nitrogen, that is, amino acids, is not only involved in anabolism in the metabolic process of yeast, but also like the carbon source in wort, that is, sugar compounds. Catabolism, through deamination, transamination, decarboxylation, etc., further participate in other metabolisms, such as tricarboxylic acid cycle, form fat and fatty acid, form keto acid and sugar, etc., through complex metabolic process, play a role in flavor composition. important influence. The number and composition of amino acids are closely related to the control of the protein resting process. In addition, some components in the decomposition products of protein also have a direct impact on the flavor of beer, such as sulfhydryl-containing proteins or amino acids.

(5) The process of protein rest is closely related to the abiotic stability of beer, because the main components of beer turbid particulate matter and turbid parent material are proteins with a certain relative molecular mass. By means of protein removal, including strengthening the precipitation of coagulable nitrogen, removal of hot and cold coagulants, and later adsorption of protein, the abiotic stability of beer can be effectively improved, and the control of protein resting process has very important role.

(6) The protein resting process is also related to the color of beer, the removal of polyphenols, and the formation of bubble caps in the production process. Amino acids generated by protein decomposition can react with monosaccharides to form pigment substances in melanoid reactions. , the condensation of polyphenols can polymerize with proteins to form cold coagulates, and the foam caps produced by fermentation are mainly composed of hop resin and protein. The material conditions for these reactions.

The control of the protein resting process should be a key process in the wort manufacturing process, and it plays an important role in the subsequent beer production process and beer quality control.