5. Selection and degradation of yeast species
It is very important to choose a kind of yeast which is suitable for the production needs of each brewery. For example, if the current mainstream 16 ° P beer is brewed, the main fermentation temperature is above 13 °C, and a yeast suitable for high temperature and high density brewing must be selected; At this time, if you also choose to ferment with yeast suitable for medium temperature and middle density, then the turbidity of the fermentation liquid is likely to be high; And vice versa.
In addition, after selecting a suitable strain, it should also prevent the degradation of yeast strains after long-term use. The causes of yeast degradation are roughly divided into:(1) Yeast's own variation, and the more yeast is preserved and transferred, the more likely it is to mutate and produce degradation. (2) The addition of yeast is inappropriate. When yeast is inoculated with yeast, excessive yeast is likely to cause relatively few new cells of yeast, and there is a lack of nutrition in the later period. As the use of yeast algebra increases, yeast degrades and ages; The addition of yeast is too small, which is detrimental to the suppression of miscellaneous bacteria. It also prolongs the main fermentation time and causes yeast premature aging. (3) Contamination of miscellaneous bacteria.
(1) First, a yeast strain suitable for fermentation needs to be selected.
(2) Prevention of yeast degradation: 1 Strengthen yeast management, select suitable species preservation conditions, strengthen microbial monitoring during the transfer process to prevent contamination of bacteria. 2 Control the method of using yeast mud, choose the best recycling time of yeast mud, calculate the best addition amount, control the use of algebra yeast.
(3) Strengthening the "nutrition" of yeast growth: The ingredients of wort are unreasonable. For example, too little α-amino nitrogen in wort can lead to poor yeast development. Zinc is a Cofactor of alcohol dehydrogenase, and zinc deficiency in wort can also cause yeast degradation. (Note: This article refers to the first item I proposed. The quality of malt is poor, so beer brewing is an "art of the middle" and every link needs to find the best balance.)
6. Length of storage period and discharge of yeast
After the main fermentation is over, the beer cools down to about -1 °C and enters the wine storage period. It takes a certain period of time to precipitate the yeast and form a beer flavor substance. However, the excessive storage period will have a negative impact on the turbidity of the wine body. Some yeasts suspended in the wine body will self-dissolve, and the protein content of the wine body increases, resulting in a vulcanization taste, which will make the turbidity of the fermented liquid increase. Even if it is serious, thermal turbidity occurs. At this time, yeast emissions during the storage of wine are quite important, and they can begin to discharge more frequently and discharge once every two days. By the end of the storage period, yeast deposition can be appropriately relaxed when the emission frequency, can be discharged once every three days.
(1) Develop a rational discharge mechanism for yeast.
(2) To properly control the drinking age, the production department must timely arrange and adjust the production according to the marketing plan of the sales department to ensure a suitable drinking age.
7. Process control of wine filters
The suspension in the fermentation liquid brings difficulties to the subsequent wine filtration, increases the amount of soil consumption, and reduces the production efficiency. When the fermentation liquid with poor raw materials is filtered, it often appears that even if the number of fermentation liquid canning cells is not high, the pressure difference rises faster when filtering, because the β-glucan residue in the fermentation liquid is high. However, even if the quality of the fermentation liquid is even better, as long as there is a problem with the filtration process, the turbidity of the finished product will be high. Therefore, no matter whether the quality of the fermentation liquid is good or bad, it is necessary to strengthen the inspection during the process of filtering wine, find out the problems and solve them in time. Taking candle-type filters as an example, the following points must be done to reduce the turbidity of the finished product:
(1) Ensure the pre-coating time and quality, because the quality of the pre-coating soil layer will directly affect the turbidity of the finished product.
(2) The proportion of yeast cells in the wine body based on the quality of the wine body and the number of yeast cells in the wine body.
(3) The gas of the pre-coating filter must be discharged, otherwise it will affect the pre-coating effect; The relevant pipeline gas must be drained before filtration, otherwise the gas will impact and destroy the precoating.
(4) Fermentation tanks are stable for pressure and avoid the impact of pressure difference on the soil layer caused by high and low.
In short, when the turbidity of beer is high in production, it must be comprehensively analyzed and the cause gradually eliminated. Brewing low turbidity and high quality beer. High quality malt, excellent yeast strain, good health guarantee, stable saccharification, fermentation, filtration process, perfect sales plan and other factors are indispensable. This is not only a test for brewing workers, but also a test of the management level of an excellent beer company.