Effects of high-temperature pressure cooking on cold-grind and blanched soymilk: Physico-chemical properties, in vitro digestibility and sensory quality

Abstract

The present work investigated effects of high-temperature pressure cooking (HP) on physico-chemical properties and in vitro protein digestibility of cold-grind soymilk (CS) and blanched soymilk (BS). Confocal laser scanning microscopy presented that proteins and lipids in BS were obviously coalesced compared with CS, while HP treatment contributed to homogeneous dispersion of protein and lipid. Particle size of the BS and BSHP were larger than that of CS and CSHP. Tertiary structure of protein suggested that hydrophobic interactions and disulfide bonds in CS and CSHP were main force among protein molecules. Meanwhile hydrophobic interactions were account for 70% of the total bonds in BS and BSHP. The maximum fluorescence excitation wavelength (λ_max) of BSHP (349.0 nm) was shown a red shift compared with CS (346.5 nm). For secondary structure of protein, β-sheet was 30.61% in CS, while CSHP, BS and BSHP decreased by 2.65%, 5.73% and 7.77%, respectively. Thus, the protein in BS and BSHP were evidently aggregated, loose and disorder; while the CS and CSHP protein were dense and orderly. Also, HP treatment led to loose and unordered protein structure. Moreover, the in vitro digestibility was BSHP > BS > CSHP > CS. The difference in digestibility of four soymilk was determined by the protein structure. Sensory evaluation showed that blanching treatment effectively reduced beany flavor and HP decreased the diameter of oil bodies of BS, which led to smooth mouth feel and thus the highest global impression of BSHP.

Keywords: Aggregation; Blanched soymilk; Cold-grind soymilk; Digestibility; High-temperature pressure cooking; Protein spatial structure.