Preparation Of Soybean Protein Isolate For Sausage And Its Application

Soybean protein isolate (SPI) severing as a functional ingredient, has been widely usedin processed meat products. Gelling, water holding capacity (WHC) and other properties ofcommercial SPI are inferior to myofibrillar proteins. The addition of SPI alternative to meatscould lead to the reduction of myofibrils-based product quality. As for sausage, its texturalproperties (e.g.: hardness) and water hydration property possibly loss during storage. In thispaper, the objective of current research was to use SPI applied in a sausage with high level ofcontent to evaluate the possible mechanism(s) and appropriate approaches for SPImodifications, and ultimate goal was to meet the requirement of sausages contained rich SPIand promote the scope of SPI applications.In the sausage system, the effects of amount of low-denatured SPI and commercial SPI(10-70%of lean protein, w/w) on the sausage were, respectively, systematically investigated.The cooking loss of sausage increased and hardness, chewiness, and the adhesive of sausageall decreased significantly with the increased of SPI addition level. The cooking loss ofcommercial SPI treatment was significantly lower than that of low-denatured SPI treatment,and the higher hardness, chewiness, gumminess values were obtained for the commercial SPItreatments. Moreover, the gel properties and emulsifying property of commercial SPI weresuperior to those of low-denatured SPI. The results suggested that reducing the temperature ofgel point and enhancing the gel properties of SPI could improve the quality of sausagecontaining SPI.Accordingly, the effect of manufacture processes of SPI on the temperature of gel pointand gel properties of SPI was also studied. The temperature of alkali soluble stage and acidsinking affected gel properties of SPI significantly. The ultra high temperature (UHT) heatingbefore spray drying could improve gel properties of SPI (12%, w/w) under80℃.The optimalcondition was heat treatment in the alkali soluble stage under60℃, and then under40℃inthe acid sinking stage, then under130℃in neutralization stage, significantly increased thegel properties of SPI130which the temperature of gel point was62.6℃. The gel strength ofSPI130was54g which could improve440%compared to low-denatured SPI, and the WHC ofSPI130was42%which could improve58.3%. The results of gel properties of SPI and MPI(12%SPI:4%MPI,1:1, w/w)showed that, SPI with stronger gel strength could make a bettermix protein gel of SPI and MPI. The gel strength and the WHC of the mixed protein gelcontaining SPI130was88.6g and53%, respectively, which improved107%and11.3%compared to the mixed protein gel containing low-denatured SPI, and were significantlylower than those of MPI (4%, w/w).there was no significantly difference in the WHC ofmixed protein gel contain denatured SPI.The effect of pre-emulsification on the mixed protein gel properties was examined. Theresults showed that pre-emulsification could improve the gels strength and the WHC ofSPI-MPI significantly. The gel strength (256g) of mixed protein gels containing（12%SPI130:4%MPI,1:1, w/w）SPI130which was emulsified with water and oil at the ratioof12:44:44, were higher than that (210g) of MPI (4%, w/w). The WHC of the mixed protein gels with pre-emulsification was25%higher than that of the mixed protein gels withoutpre-emulsification, which was closed to that of the gels of MPI (4%). The resultsdemonstrated that pre-emulsification could improve the quality of meat product containingSPI under UHT heat treatment.Finally, the effect of UHT heat treatment and pre-emulsification on the real sausagecontaining SPI was verified. Pre-emulsification could enhance the role of SPI130played in themeat product. With the addition of10%-30%, there was no significant difference of thehardness, chewiness, and the adhesive of sausage between the sausage containing SPI130which was emulsified with water and oil at the ratio of12:44:44and the all meat sausage,while cooking loss was2~3%less than that of all meat sausage. With the60%addition, thehardness was7821N,21%lower than that of all meat sausage, while41%higher than that ofthe sausage containing SPI130without pre-emulsification and62.5%higher than that of thesausage containing commercial SPI; Cooking loss was11.18%, which was lower than that ofall meat sausage and similar to that of the sausage containing commercial SPI. The resultconfirmed that reducing the temperature of gel point and enhancing the gel properties of SPIcould improve the quality of sausage containing SPI, and pre-emulsification could alsoimprove the quality of sausage containing SPI. This has a significant guiding for health meatproduction of sausage with high SPI and low fat, and broadens the application field of SPI.