The method of brewer s yeast propagation, the beer fermentation process

1. Purpose of the experiment:

Learn about yeast.

Expanded culture method to prepare strains for laboratory beer fermentation.

Second, the experimental principle:

Before beer fermentation, a sufficient amount of fermentation culture must be prepared. In beer fermentation, the inoculum amount should generally be 10% of the wort amount (so that the amount of yeast in the fermentation broth reaches 1 107 yeast ml), so for large-scale fermentation, it is first necessary to expand the yeast culture. The purpose of expanding the culture is to obtain a sufficient amount of yeast on the one hand, and to gradually adapt the yeast from the optimal growth temperature (28) to the fermentation temperature (10) on the other hand.

3. Experimental equipment:

Constant temperature incubators, biochemical incubators, microscopes, etc.

4. Experimental Procedure:

In this experiment, 60 liters of wort were used, so 6000 ml of yeast containing 1 108 ml of yeast should be prepared, and about 600 ml of culture should be prepared for each group based on 10 groups per shift. The recommended process is as follows:

Expansion of culture: Wort bevel.

Strain Wort plate - 28, 2 days Microscopic examination, pick 3 single colonies, inoculation 50ml wort test tube (or triangular bottle) - 20, 2 days (shake 3 times a day) 550ml wort triangle flask - 15, 2 days (shake 3 times a day) Count and set aside.

1.Preparation of culture medium.

Take the wort filtrate (about 400 ml) prepared by the agreement method, add water to about 600 ml, take 50 ml and put it into a 250 ml triangular bottle, and another 550 ml to 1000 ml triangular bottle, wrap the bottle cloth, and sterilize the MPA for 30 minutes.

2.Expanded culture of culture.

According to the above process, the expanded culture of the strains was carried out (the inclined activated strains were provided by the teacher). Pay attention to aseptic procedures.

5. Precautions: There will be a lot of precipitation in the sterilized medium, which will not affect the reproduction of yeast. To reduce precipitation, the medium can be boiled well and filtered prior to sterilization.

6. Reflection question: Why should the strain expand slowly during the expansion process, and why should the culture temperature decrease step by step?

Supplement: The following yeast fermentation technology is basically used in China; Now the fermentation temperature and fermentation time have changed greatly. It is mainly determined according to the characteristics of different yeasts, and the main fermentation temperature is usually 10 15 degrees, and at the same time, it is slightly adjusted according to the market taste feedback, which is generally a deviation of 1 degree.

The first volume of the high school biology book, the process of anaerobic respiration, is roughly like this.