Influence Of Soybean Protein Composition On Yield Of Soybean Protein Isolate

Soybeans contain around40%of high quality protein and20%of oil, have become themajor source of edible oil, and the meal provides an important source of protein and otherminor active components. The major soybean seed protein composition can be classified into2S,7S,11S, and15S components. However, recent research found that should involve theoleosin which covered much of the oil body surface. The most refined forms of soybeanprotein product by industry are the soybean protein isolates, which contain90%or moreprotein. Soybean protein isolates has two main fractions: β-conglycinin (7S) and glycinin(11S). This thesis was mainly devoted to improvement of industrial processing of soybeanprotein isolates and targeted protein compositions which selected factors as they relate to theyield of soybean protein isolates.The extracted2S、7S and11S fraction from meals were surveyed and the proteincomposition of the two meals were compared. The content of7S and11S in high-proteinmeal B is higher than low-protein meal A, while the content of2S in high-protein meal wassignificantly lower than the low-protein meal. The result reflected that the macromolecularprotein in high-protein meal was a little higher than the low-protein meal. Therefore, we canconclude that the main reasons of the low extraction rate from high-protein meal were thetraditional process can not extract the protein adequately.The TEM and SDS-PAGE were applied to observe oil body and characterize oleosinsfrom four soybean cultivars. The results showed that oleosin contents are independent of theoil contents but consistent with the protein contents entirety, the size and shape of the oilbodies are dictated by the ratio of lipids in seeds to oleosins. The solubility of soybeanoleosins were poor entirely, especially,34kDa and17kDa were lowest. The low yield of SPIfrom high protein soybean meal may be duo to the low alkaline solubility of the bands.The roles of lipophilic protein-PL in soybean meals were examined. The proteins may berecovered as lipophilic proteins associated with phospholipids in the acid precipitated proteins,which include β-conglycinin and glycinin. Comparative results showed that the high-proteinmeal contained less lipophilic proteins than the low-protein meal. This was also one of thereasons which ultimately affected the extraction rate soybean protein isolates.The effects of different extracting conditions on yield and quality of protein fromsoybean meals were studied. The two meals protein contents were different, and theextraction rate of protein isolates were different in the same process. Optimum second extraction conditions determined by orthogonal test analysis were as follows: temperature45℃, time25min, adding water by1:10, pH8.4. Pilot plant testing showed that the residueprotein of high-protein meal was23.22%while19.35%for low-protein meal, the reductionrate were4%and2%, respectively. For the case of residue protein of high-protein mealremains high, the laboratory has developed a new process which made it fell to19.68%,effectively improved the extraction rate, and the products got high quality in protein content,color, and the functionality. Profit calculations show that the process improvements canimprove the plant’s economic benefits effectively.This paper obtained the influencing factors of soybean protein components on itsextraction rate, including not only the storage protein fractions, as well as oleosin in soybeanseeds and lipophilic protein-PL in soybean meal.The results and the process improvement ofthis paper may be conducive to the industrial process of high-protein soybean meal.