Ice Recrystallization Inhibition Activity of Soy Protein Hydrolysates

Identifying and developing ice recrystallization inhibitorsfromsustainable food proteins such as soy protein isolate (SPI) can leadto practical applications in both pharmaceutical and food industries.The objective of this study was to investigate the ice recrystallizationinhibition (IRI) activity of SPI hydrolysates, and this was achievedby using an IRI activity-guided fractionation approach and relatingIRI activity to interfacial molecular activity measured by vibrationalsum frequency generation (VSFG). In addition, the impact of molecularweight (MW) and enzyme specificity was analyzed using three differentproteases (Alcalase, trypsin, and pancreatin) and varying hydrolysistimes. Using preparative chromatography, hydrolysates from each enzymetreatment were fractionated into five different MW fractions (F1-F5),which were then characterized by high-performance liquid chromatography(HPLC). All SPI hydrolysates had IRI activity, resulting in a 57-29%ice crystal diameter reduction when compared to native SPI. The F1fraction (of 4-14 kDa) was most effective among all testedhydrolysates, while the lower MW peptide fractions lacked activity.One sample (SPI-ALC 20-F1) had a 52% reduction of ice crystal sizeat a lower concentration of 2% compared to the typical 4% used. SFGshowed a difference in H-bonding and hydrophobic interactions of themolecules on the water/air interface, which may be linked to IRI activity.This study demonstrates for the first time the ability of SPI hydrolysatesto inhibit ice crystal growth and the potential application of SFGto study molecular interaction at the interface that may help illustratethe mechanism of action.