Soy protein isolated extraction process
Protein extracted from soybean meal, add water, pH, temperature, extraction time yield of protein isolate has a great influence.
Soak: Many companies are first crushed and then dry soybean meal mixed with water extraction. Dry grinding is not conducive to raising the rate of protein extraction, and thermal denaturation of proteins tends to reduce the protein value of NSI. If defatted soybean meal with water to soak for some time to refining, which can effectively improve the protein extraction rate. After refining the method of the first soaking the dry method is more in line with crushed and then soaked in the dissolution mechanism of soy protein. It was determined that the first method than dry after soaking crushed and then soaked in refining protein extraction rate of 2 to 4 percentage points.
Water extraction of soy protein, add more water, the higher the rate of protein extraction, but too much water, and acid whey liquid when the increase in globulin, protein loss also increased, but the yield of finished products down; if too little water, soy protein significantly decreased the rate of dissolution, the finished product yield will fall. Follow-up will increase the difficulty of the process. While the refining stage, slurry particle size and more details of protein extraction yield higher results. In actual fact, when the slurry particle size is too small so they will yield and protein extraction effect is reduced, while increasing the difficulty of teaching the filtration and separation.
Protein solubility and extraction of PH have a great relationship, pH is too low, when, 11s protein components can be dissociated into 2s component, this dissociation effect begins to create pH3.75 PH2 reached a peak when the pH less than 2, will send the polymerization to form polymers. If the ph is too high, because of too alkaline will cause deamination decarboxylation of peptide bond cleavage, will happen "bladder Lai reaction", the amino acids into toxic compounds. Therefore, the PH protein extraction must be the appropriate control.
With the alkaline solution extracted soybean meal in protein, high and low temperature on protein NSI has a great influence. In general, with the extraction temperature, NSI decreased. When the temperature exceeds 55 ℃, the protein started denaturation temperature than 80 ℃, the protein will form a gel. Therefore, extraction temperature, protein denaturation will not only affect its functionality, and viscosity increase, separation difficulties, separation energy increase.
The choice of extraction time, mainly to see the dissolution rate of protein. In general, certain extraction conditions, the longer extraction time, protein content, the higher the rate. But when a certain period of time after extraction, protein extraction yield with the extension of time without significant changes. We have to considering energy consumption, equipment turnover, production cycle, technology costs and other factors to determine the reasonable period of time.