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Powder-level mechanisms of soy protein isolate functional deterioration during storage: The interplay of aggregation
Hui Zhang1, Tong Zhang1, Xiong Zhang1
1Beijing Key Laboratory of Plant Protein and Cereal Processing, College of Food Science and Science and Nutritional Engineering, China Agricultural University, Beijing 100083, PR China.
Abstract:
Soy protein isolate (SPI) often undergoes functional decline during storage, yet the underlying mechanisms remain unclear. This study investigated the relationship between powder-level changes and functional loss. Following four weeks of storage, SPI showed a 42.1 % decrease in solubility and reduced gelation and emulsifying abilities. These changes corresponded with significant aggregation, a 29.1 % increase in particle size (p < 0.05). The surface free energy was also reduced, indicating impaired wettability and hydration. Oxidative modifications were also detected, including elevated carbonyl levels and conformational relaxation. Meanwhile, the peptide backbone remained mostly intact. The results suggest that powder aggregation, along with oxidative structural changes, jointly hinder hydration and dispersion. This combined effect leads to functional deterioration. This study provides mechanistic insights into SPI instability and offers a reference for improving the storage stability of plant protein powders.
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