Enhancing emulsifying properties of soy protein isolate-wheat starch conjugates: exploring the influence of starch ratio and hydrolysis time

This study aimed to assess the impact of starch ratio and hydrolysis time on the functional properties of protein-polysaccharide conjugates. Mixtures were prepared, containing 4% total biopolymer by weight, with soy protein isolate (SPI), and both raw and hydrolyzed wheat starch, at ratios of 1:1, 1:2, and 1:3. The Maillard reaction was conducted at 90 °C and pH 9 for 6 h. Complex formation between the biopolymers was confirmed using electrophoresis and FTIR analysis. Compared to SPI, the conjugates exhibited reduced hydrophobicity, minimal increase in particle size during storage (< 36%), high water absorption (> 68%), and enhanced solubility (> 65%), especially near the isoelectric point. The conjugates prepared with a 1:3 ratio from native starch and a 1:1 ratio from hydrolyzed starch (60 min) demonstrated superior emulsifying properties, attributed to their smaller initial particle size. Overall, by optimizing the starch-to-protein ratio and starch hydrolysis time, a balance between hydrophobic and hydrophilic groups was achieved, resulting in improved emulsification and prevention of particle size increase.