Requirements for stirring in saccharification-related process

Stirring is an important operation in the saccharification process, and different saccharification stages have different stirring requirements. What are the requirements for stirring operations in the processes of feeding, protein rest, gelatinization, and saccharification:

The mixer of each pot of the saccharification system should have at least two stirring speeds, the fast speed is 30~40r/min, the slow speed is 10~15r/min, but the stirring line speed is generally 2.6~3.0m/s, this is to adapt It is designed according to the process requirements of different time periods.

When feeding materials, relatively fast stirring is generally used, so that the dry materials can be fully mixed with water, continuously dispersed and absorbed in the mash, and the materials will not be deposited on the bottom of the pot or "clumped"; however, in the mash In less cases, consider using a slightly slower stirring speed, because fast stirring tends to throw the mash against the surrounding pot walls.

Usually in the process of protein rest, it is often not stirred, and this process is very similar to the general soaking method. Theoretically speaking, stirring should be carried out during the protein resting process, because this is conducive to the dispersion and dissolution of materials, and is conducive to the dissociation and action of enzymes. However, due to factors such as the material-water ratio of malt mash during protein resting, the stirring is not uniform. Moreover, in actual effect, the difference between whether stirring or not is not too big, so in consideration of energy saving, stirring may not be carried out.

Stirring during gelatinization and liquefaction is very important, because the gelatinization process of materials has a change process such as suspension → colloidization → liquefaction → resuspension. When the mash is thick, the heat can be transferred evenly, and it must be stirred continuously at a faster speed; but after the mash boils, considering the auxiliary stirring effect of the boiling mash, and the mash has been liquefied , the viscosity has decreased, and a slower stirring speed can be used at this time.

Another point of view is that protein rest and stirring during saccharification may affect the effect of enzymatic hydrolysis, increase the oxygen absorption of the mash, reduce the antioxidant performance of the wine, deepen the color of the wine, and affect the flavor performance of the wine. If the speed is too slow If the purpose of uniform stirring is not achieved, power will be wasted; if it is too fast, it is easy to form shearing force, which will increase the water-insoluble substances and affect the filtration performance and abiotic stability of wort and beer.

It should be pointed out that different operating practices have different views on whether the protein rest and saccharification process should be stirred or not.