Sodium Succinate-Assisted Hydrolysis of Soy Protein Isolate Improves Umami and Saltiness Enhancement Through Amino Acid and Peptide Redistribution

Abstract

Soy protein isolate hydrolysates (SPIH) are promising plant-derived taste modulators, but strategies that improve both taste intensity and temporal persistence remain limited. Sodium succinate (SS) was introduced before enzymatic hydrolysis to prepare SS-SPIH, and the product was compared with hydrolysates receiving SS after hydrolysis (SPIH + SS). SS-assisted hydrolysis reduced the degree of hydrolysis from 19.21% in SPIH + SS to 17.81% in SS-SPIH, while increasing total free amino acids from 26.21 to 32.74 mg/mL and total quantified N-succinyl amino acids from 2.95 to 4.64 μg/mL. These results suggest that SS addition before hydrolysis altered the low-molecular-weight composition of SPIH rather than simply increasing the overall extent of proteolysis. Neither hydrolysate showed intrinsic umami or saltiness in water at 30 mg/L. In monosodium glutamate (MSG) and NaCl model systems, SS-SPIH showed stronger umami- and saltiness-enhancing effects than SPIH + SS, especially at 30 mg/L. Temporal sensory analyses further showed stronger umami dominance, with the temporal check-all-that-apply (TCATA) umami citation proportion remaining above 0.5 for 67.9 s and the time-intensity (TI) umami extinction time reaching 90.00 s. These results suggest that SS-assisted hydrolysis improves the umami- and saltiness-enhancing performance of SPIH, likely through coordinated changes in free amino acids and N-succinyl amino acids.

Graphical Abstract