title: Effects of phytase-assisted processing method on physicochemical and functional properties of soy protein isolate.
abstract: Phytate is an important antinutritional factor in food products. In this study, a phytase-assisted processing method was used to produce low-phytate soybean protein isolate (SPI) samples, and their physicochemical and functional properties were examined. Hydrolysis condition at low temperature (room temperature) and pH 5.0 was better than that recommended by manufacturer (pH 5.0, 55 °C) at keeping the properties of SPI, so the former condition was selected to prepare SPI samples with phytate contents of 19.86-0.11 mg/g by prolonging hydrolysis time (0 (traditional method), 5, 10, 20, 40, and 60 min). Ash content (R(2) = 0.940), solubility (R(2) = 0.983), ζ-potential value (R(2) = 0.793), denaturation temperatures (β-conglycinin, R(2) = 0.941; glycinin, R(2) = 0.977), emulsifying activity index (R(2) = 0.983), foaming capacity (R(2) = 0.955), and trypsin inhibitor activity (R(2) = 0.821) of SPI were positively correlated with phytate content, whereas protein content (R(2) = 0.876), protein recovery (R(2) = 0.781), emulsifying stability index (R(2) = 0.953), foaming stability (R(2) = 0.919), gel hardness (R(2) = 0.893), and in vitro digestibility (R(2) = 0.969) were negatively correlated with phytate content. Simulated gastrointestinal digestion and subsequent dialysis showed that percentages of dialyzable Zn and Ca were increased with decreasing phytate content, whereas the amounts of dialyzable Zn and Ca revealed different behaviors: the former was increased and the latter was decreased. Circular dichroism spectra showed that secondary structure of SPI was changed by phytase. Compared with traditional processing method, the phytase-assisted processing method could produce SPI with lower phytate and higher protein contents, which had better in vitro digestibility and could be used to prepare gels with higher hardness by partially losing some other functional properties.
authors.affiliation: State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University , 1800 Lihu Avenue, Wuxi, Jiangsu Province 214122, People's Republic of China.
authors.forename: Hongjian
authors.initials: H
authors.lastname: Wang
authors.forename: Yeming
authors.initials: Y
authors.lastname: Chen
authors.forename: Yufei
authors.initials: Y
authors.lastname: Hua
authors.forename: Xiangzhen
authors.initials: X
authors.lastname: Kong
authors.forename: Caimeng
authors.initials: C
authors.lastname: Zhang
mesh_terms: D010832:6-Phytase / Q000737:chemistry*; D005511:Food Handling; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D010833:Phytic Acid / Q000737:chemistry*; D012995:Solubility; D030262:Soybean Proteins / Q000737:chemistry*; D013025:Glycine max / Q000737:chemistry*
chemical_list: D030262:Soybean Proteins; D010833:Phytic Acid; D010832:6-Phytase
keywords: digestibility; emulsifying; foaming; gelation; hydrolysis condition; phytase; phytate; solubility; soybean protein isolate