Characteristics of Wort
The rate of fermentation depends primarily on the level of separation between cold and hot coagulants in the wort, oxygen supply to the wort, and the composition of the wort. The cold coagulum forms when the wort is boiled due to protein denaturation and aggregation, as well as the continuous oxidation and polymerization of polyphenols in the wort. Cold coagulum refers to the agglomerated protein and polyphenolic substances produced during the cooling process of the wort.
The rate of alcoholic fermentation increases significantly with higher temperatures, while fermentation slows down at lower temperatures. Proper temperature adjustment and control during the main fermentation process is crucial for effective fermentation management. Accurate temperature adjustment can determine the fermentation degree. Improper temperature adjustment can lead to abnormal fermentation, especially if there are high fluctuations in temperature. This can result in premature yeast precipitation, weakened fermentation power, no sugar reduction at the end of fermentation, low fermentation degree, weak bubble formation, or insignificant bubbling during the high bubble period. Once the main fermentation begins, the yeast gradually propagates, and the fermentation temperature gradually increases. The natural heating method is used to raise the temperature from the initial temperature to the high fermentation temperature. When the maximum fermentation temperature is reached, the cooling pipe is employed to control the temperature and facilitate further temperature increase through the use of cooling water. The cooling process should be gradual to avoid yeast precipitation and to ensure proper fermentation.
The contact area between yeast cells and wort is crucial for the transformation of materials. The contact area expands with increasing yeast cell concentration. Less yeast is required when fermentation starts earlier. The actual dosage should be determined based on the freshness and consistency of the yeast, as well as the number of yeast generations used. If the inoculation temperature is low, a slightly larger inoculation amount is recommended, and vice versa. The total amount of yeast added depends on the start time of fermentation. It is generally recommended to add yeast shortly after the start of fermentation to inhibit the growth of other bacteria.
Mechanical movements in beer equipment, such as circulation and stirring, enhance the contact between yeast cells and wort, resulting in vigorous fermentation. Mechanical action increases wort circulation, allowing yeast to come into full contact with sugar and oxygen, thereby promoting initial fermentation. Traditional one-tank or two-tank methods for beer production typically employ static fermentation without stirring in the main fermentation equipment. Circulation is primarily achieved through differences in carbon dioxide concentration.
The change in sugar content is reflected in the final parameters of beer fermentation: true fermentation degree and apparent fermentation degree. True fermentation degree is determined by adding water to the original volume after evaporating the ethanol in the wine, measuring its concentration, and calculating the true degree of fermentation.