Synergistic modification of soy protein isolate using transglutaminase and magnesium chloride: A sequential treatment strategy for dual allergenicity and digestibility benefits

Soy protein isolate (SPI) is a widely utilized food ingredient, but its application is constrained by inherent allergenicity. Structural modification of SPI to mitigate allergenic potential while preserving nutritional quality represents a significant challenge. This study investigated a combined enzymatic and ionic approach to address this issue. SPI was treated individually with transglutaminase (TGase, ST), magnesium chloride (MgCl₂, SM), or sequentially with TGase followed by MgCl₂ (STM). Structural analyses revealed that the sequential STM treatment induced the most substantial protein aggregation, secondary structure alteration, and free sulfhydryl reduction. Correspondingly, it most effectively suppressed IgE binding capacity, outperforming individual treatments. During in vitro digestion, STM samples exhibited gastric resistance but yielded the highest intestinal peptide release, a 20.3% increase over control. These findings demonstrate that the sequential TGase-MgCl₂ treatment synergistically modifies SPI structure, effectively mitigates allergenicity, and enhances protein digestibility, thereby offering a viable strategy for developing hypoallergenic soy-based food products.