Gelation Properties of Transglutaminase-Induced Soy Protein Isolate and Wheat Gluten Mixture with Ultrahigh Pressure Pretreatment
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In this study, we elucidated the microbial transglutaminase-induced gelation properties and thermal gelling ability of soy protein isolate (SPI) and wheat gluten (WG) mixture following ultrahigh pressure (UHP, 100–400 MPa) pretreatment. UHP treatment induced unfolding and aggregation within SPI/WG protein molecules, which led to increases in free sulfhydryl group content and surface hydrophobicity. However, the transglutaminase cross-linking reaction facilitated the formation of hydrophobic interactions and disulfide bonds and thus resulted in higher gel strength, water holding capacity, and denser and more homogeneous gel networks of transglutaminase cross-linked SPI/WG gels. Rheological measurements revealed that the addition of UHP steps might generate a higher storage modulus (G′) value of MTGase-induced SPI/WG gelation during the heating-cooling cycle (25 °C → 95 °C → 25 °C). Our results indicated that various chemical interactions including covalent interactions (i.e., ε-(γ-glutamyl)lysine bonds and disulfide bonds) and non-covalent interactions (i.e., electrostatic forces and hydrophobic interactions) were involved in SPI/WG gel network structures. Hydrophobic interactions and disulfide bonds are significantly increased with the pressure level (100–400 MPa) compared with that of the unpressurized control. Furthermore, UHP treatment reduced the α-helix and β-turn content but increased the β-sheet and random coil structures. Thus, UHP treatment may be considered as a novel technique to expand the utilization of SPI/WG mixture in the food protein gelation industry.
KeywordsUltrahigh pressure Gel properties Microbial transglutaminase Soy protein isolate Wheat gluten
This research was funded by the National High Technology Research and Development Program (863 Program) of China (No. 2013AA102201), the Key program of the National Natural Science Foundation of China (No. 31271931), and the Key Scientific and Technological Project of Anhui Province of China (No. 1301031031 and 15czz03096).
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