Effect of microwave treatment and alternate drying methods on functional properties of soy protein-sodium alginate conjugates

This study investigated an energy-efficient, scalable approach to manufacturing functionally improved sodium alginate conjugates with soy protein isolate via rapid microwave glycation and drying methods. Microwave treatment for 4 min (power level- 160 W, 320 W) significantly enhanced conjugation compared to water bath heating for same duration, yielding improvements in overall functionality. Notably, 160 W favored foaming capacity (75.05%), thermal stability (94.7 °C), emulsifying activity index (314.6 m²/g), zeta potential (− 42.5 mV), and particle size (0.96 μm), while 320 W maximized water-holding capacity (7.17 g/g) and apparent viscosity (248 cP). Higher SA content in SPI-SA-160 gave favorable changes in functional groups as depicted through FT-IR analysis. These changes were responsible for enhanced thermal stability, zeta potential, emulsifying, and foaming properties. Evaluation of six drying techniques (freeze, oven, vacuum, refrigeration, foam mat, spray) revealed that spray drying preserved color, and both spray and foam mat drying achieved functional traits like emulsifying properties and oil holding capacity comparable to freeze drying. Oven drying had a detrimental effect on functional properties due to the denaturation of soy protein at high temperatures. The findings suggest a combination of microwave glycation and spray drying has potential for cost-effective emulsifier production, and microwave treatment with foam mat drying is suitable for scalable emulsifier, binding, and foaming applications.