Comparative Effect of Physical Field Processing Techniques on Soybean Protein Digestibility and Probiotic Bile Acid Metabolism.

Food processing is essential for ensuring food safety, as it can alter protein structure and digestive properties, regulate the bioavailability of dietary nitrogen, and further affect gut probiotics. In this study, three physical field processing methods, namely far-infrared radiation heating, hot-air convection heating, and microwave dielectric heating, were used to systematically investigate the structure-activity relationship of processing-induced changes in protein structure and digestive characteristics on the proliferation and bile acid metabolism of Lacticaseibacillus paracasei 207-27 (LP27) and Bifidobacterium breve 207-1 (BB1). The results showed that microwave treatment increased soybean protein digestibility (35.59 ± 0.57%), whereas convection heating (27.32 ± 0.39%) and infrared heating (24.09 ± 0.38%) decreased it. Soybean protein treated with microwave had a higher surface hydrophobicity (142.46 ± 6.49 Ho), which was significantly higher than that of the infrared treatment (96.50 ± 3.54 Ho) and the convection heating (50.54 ± 4.28 Ho). Microwave heating enhanced the prebiotic potential of soy protein thereby supporting higher growth and bile acid metabolism in both probiotic strains. Soy protein-treated with convection heat showed potential for restoring bile acid metabolism in BB1 but not in LP27. Infrared treatment was effective for enhancing bile acid metabolism in LP27 but inconsistent in BB1. The study highlights a practical strategy for adapting heat processing techniques to enhance the prebiotic potential of plant proteins for mediating strain-specific probiotic bile acid metabolism and gut health.