Why sugar content cannot be lowered in fermentation

During the main fermentation process, the sugar content does not fall or falls very slowly. We analyze some possible main reasons from the three aspects of yeast performance, wort fermentability and fermentation process, such as:

* The number of yeast cells added is too small. If the number of yeast cells added by Lager is less than 10 million/mL, it can be seen that the fermentation hypoglycemic is obviously slowed down. Poor oxygenation and low oxygenation will also result in a decrease in the number of yeast cells and a lower number of yeast cells. If the yeast coagulation performance changes or is affected by the external agglutination factor, the yeast will coagulate and settle prematurely, so that the total number of yeast cells in the fermentation process will decrease rapidly, and the rate of hypoglycemic will slow down or even not reduce the sugar in the later stage. That is to say, the slower rate of glucose reduction in the early stage is mostly caused by too little yeast added and the yeast reproduction rate is too low. In the later stage, the slower sugar lowering is caused by the premature aggregation and sedimentation of the yeast, which causes the yeast cells to decrease sharply.

* The ability of different yeast species to utilize maltotriose is different. If the ability of yeast to use maltotriose is poor or the ability to utilize maltotriose is changed, not only will the slowing rate of sugar reduction be slowed down, but also the amount of residual extract. Increasing, and yeasts with poor maltotriose capacity are prone to premature coagulation and sedimentation, which also affects the rate of hypoglycemia.

* The fermentability of wort is poor. The amount of fermentable monosaccharides, disaccharides and trisaccharides is insufficient, which can not meet the need of reducing the concentration of the extract. The measured value of residual extract is too high or the measured value of fermentability cannot be determined. fulfil requirements.

* The wort cooling temperature is low, which causes the yeast to start at a slower temperature. The lower the fermentation temperature will also lower the yeast metabolic rate and slow the fermentation rate. However, this situation may lead to the comparison of pre-fermentation and hypoglycemic. Slow, but later will gradually become normal.

* The abnormality of the fermentation tank cooling system, the low temperature of the refrigerant, causing the local fermentation liquid to chill, the yeast is stimulated by cold and the metabolic activity is reduced or rapidly settled, which may also affect the rate of post-fermentation hypoglycemic.

* The malt raw material used has microbial contamination or malt agglutination factor, that is, there is abnormal PYF factor, which causes the yeast to coagulate prematurely. The number of yeast cells in the late fermentation is drastically decreased, the fermentation speed is slowed down, and the hypoglycemic sugar is incomplete in the later stage.

* The amount of fine particulate matter (including dextran particles, protein particles and cold coagulum) in the fermentation broth is too large, and a large amount is adsorbed by the yeast, which not only affects the fermentation of the yeast, but also easily causes the aggregation of the yeast to be suspended in the fermentation broth. The number of yeast cells is too small, affecting the speed of the whole fermentation hypoglycemic process.

* The cooling control of the fermenter is improper. For example, the cooling control of the segmented temperature zone is improper. The convection of the fermentation broth inside the fermenter is poor, which affects the suspension performance and material exchange of the yeast, and directly affects the rate of hypoglycemia. Or the high temperature of the refrigerant, the poor cooling effect and the partial refrigerant flow interruption, etc., may cause the local temperature of the fermenter to be higher or lower, the flow state of the fermenter changes, and the fermentation hypoglycemic is not normal.

* Yeast is too aging, fermentation performance is reduced, or reproductive capacity is reduced, and the number of new yeast cells is too small, which reduces the overall fermentation performance of yeast.

* The selected yeast species are strongly cohesive (most of the yeasts used in domestic breweries are moderately cohesive), and as long as the pH conditions or a certain proportion of metabolites change, it is easy to coagulate and sediment, resulting in abnormal hypoglycemia in the later stage.

* The pre-fermentation rate is too fast, so that the parameters of the fermentation broth change drastically, such as changes in pH, acidity, alcohol content and osmotic pressure conditions, which can change the metabolic properties and cohesive properties of the yeast, and cause premature coagulation and sedimentation. Late sugar reduction speed.

There are many factors affecting the fermentation of hypoglycemic sugar in large tanks. It is necessary to analyze the actual conditions of the production site one by one. Several main reasons are determined by the exclusion method, and then the tests are carried out separately. The raw materials, processes, equipment and should be determined according to the test results. Process measures. For example, after measuring (measuring the sugar spectrum, measuring the limit fermentation degree of wort or measuring the ratio of sugar to non-sugar), the fermentable sugar content in the wort is low, and the proportion of the auxiliary material can be appropriately reduced, the liquefaction is enhanced, and the saccharification is carried out by two. Segmental saccharification saccharification method to increase the proportion of fermentable sugar in wort; for example, after testing, it is found that there are obvious PYF factors, then the varieties of malt and excipients should be replaced, and the same malt should be used for yeast expansion, etc.