After the wort completes the saccharification process, it needs to be clarified by the filtering effect of the lees layer, and then enters the boiling process, and is cooled to a temperature suitable for fermentation by plate heat exchange to carry out the fermentation process of the beer. Therefore, the wort boiling process is wheat The important steps of juice preparation are essential for the production of beer. During the continuous boiling of the wort, the substances in the hot wort will usually undergo a series of very complex physical and chemical reactions. The combined results of these complex physical and chemical reactions will lead to varying degrees of changes in beer stability. The relationship between the stability of the substances in the beer and the quality of the final beer is very closely related. The main functions of wort boiling operation in beer production are as follows:
1. Inactivation of enzymes
Enzymes are proteinaceous substances, and each enzyme has its own inactivation temperature. High temperature is a way to lose enzyme activity. During the boiling process, the high temperature environment causes the activity of various enzymes to be lost. This effect is the most direct and the most important in the wort boiling operation. Due to the high temperature, various saccharification hydrolases such as starch hydrolase and proteolytic enzymes are denatured and lose their activity, so the stability of the carbohydrate substances that can be used for fermentation in the wort is ensured, and the resistance to the saccharification is further maintained. The balance of the various substances in the wort.
2. The leaching and isomerization reaction of substances in hops
The main components of hops include hop resin and essential oil. According to the requirements of different types of beer with different characteristics, different types of hops can be added twice or three times during boiling. To ensure that the main components of hops, such as α-acids, are more easily dissolved in the wort, bitter hop products are usually put into the wort at the beginning of boiling, which can also make the α-acid, the main bitterness provider in the bitter hops, easier to isomerize The reaction forms iso-α-acids. According to data, the pH value of wort has a great influence on the leaching degree of hop components in the wort, that is, the pH value is positively correlated with the leaching degree and isomerization of the α-acid in the hops. Therefore, controlling the pH value of wort has important guiding significance for boiling. The effect of adding fragrant hops in the late boiling stage is to give the beer the hop aroma. Hop oil is easily lost due to high temperature evaporation. Therefore, adding fragrant flowers in the later stage is equivalent to shortening the evaporation time and avoiding more hop oil components. Lost as water evaporates. Of course, the production of different types of beer has different requirements for the amount and use of hops in the boiling process. The hop addition technology should be formulated according to the characteristics of the beer, and cannot be generalized.
3. Evaporate excess water
The process of evaporating excess water is also called the concentration process of wort, which is also the most direct effect of wort boiling. The purpose of concentrated wort is obvious, that is, to increase the proportion of fermentable sugars in the wort by evaporating excess water. The more water evaporated, the greater the proportion of final sugars. According to the different requirements for the sugar content of the brewed beer type, the evaporation time can be adjusted to achieve the ideal sugar content for the beer fermentation process.
When the wort is boiled, the temperature can reach 95℃ or more, and the time generally lasts for at least 60 minutes. Therefore, the general types of harmful microorganisms will be killed due to the high temperature in this process. We usually think that the wort is the wort after the wort boiling process. It can be used as a sterile fermentation broth to enter the fermentation tank through a heat exchange device to wait for inoculation.
5. The volatilization of discordant flavor substances
There is a kind of corn-like substance in the flavor of beer-dimethyl sulfide, which is formed by the reaction of S-methylmethionine formed in the sprouting period of barley during the boiling process. The results show that with the boiling time The longer the dimethyl sulfide, the lower the content of dimethyl sulfide. According to the above theory, we can use the method of increasing the boiling intensity and time to make as much dimethyl sulfide volatilize from the wort.
6. Denaturation and aggregation of protein components in wort
Although protein can give beer a more mellow taste, some proteins have a negative effect on the flavor of beer. Studies have shown that the pH value of wort plays an important role in protein aggregation. Generally speaking, the pH value is in the range of 5.2-5.6, which is most beneficial to protein aggregation. High temperature will cause protein denaturation reaction, the solubility of the denatured protein in the wort will decrease, and the wort will be precipitated in the form of flocculent precipitation. These flocculent precipitates are then discharged after precipitation by whirling action. Based on the above theory, finding an appropriate degree to selectively remove unwanted proteins while retaining the required proteins is the key to serious research.
7. Color and taste
The influence of beer color and taste is related to Maillard reaction, which is a special reaction between sugars and amino acids. The product of Maillard reaction, like melanin, is the producer of wort color. At the same time, different sugars and different amino acids are produced. The different melanin-like products produced by the reaction have different tastes. Aldehydes are formed during the Maillard reaction. In addition, the color and flavor of the wort are also related to the pH value of the wort, which all contribute to the color and taste of beer. Important factor.