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Enhancing the functional characteristics of soy protein isolate via cross-linking catalyzed by Bacillus subtilis transglutaminase.

BACKGROUND
Although Streptomyces mobaraense transglutaminase (MTG) has been extensively applied to enhance the functional characteristics of soy protein isolate (SPI) through cross-linking, diverse transglutaminases (TGs) in nature may provide more choice in food industry. Previous researches reported that TG derived from Bacillus subtilis (BTG) exhibited better pH stability and thermostability than MTG.


RESULTS
An endeavor was tried to study the influence of BTG induced cross-linking on the properties of SPI. SDS-PAGE results indicated that almost all protein constituents (α', α, β, AS, and BS) in SPI could be cross-linked upon BTG treatment. BTG treatment also resulted in a significant increase (*P < 0.05) in SPI mean particle size. The emulsifying activity and stability were improved from 0.11535 m2 g-1 and 48.3% for native SPI to 0.13252 m2 g-1 and 83.9% for SPI treated with BTG at 6 h. Similarly, the modified SPI showed better foam activity (1.32 mL) and stability (87.6%) compared with the original SPI (0.93 mL and 56.8%). The water holding capacity of SPI gel was found to increase with time, with a value of 95.43% at 6 h. Furthermore, SPI gel' texture profiles were greatly improved by adding BTG (*P < 0.05).


CONCLUSION
The results of the present study indicated that BTG could be a promising cross-linking agent for improving the functional characteristics of SPI. As a substitute of MTG, BTG thus could be potentially used for food structure engineering to enhance the functional characteristics of multiple proteins to advance the development of food chemistry. This article is protected by copyright. All rights reserved.