Formation of high-elasticity and high-strength semitransparent ovalbumin gel induced by alkali-heat treatment

Abstract

ABSTRACT The objective of this study was to prepare high-elasticity and high-strength ovalbumin (OVA) gels by comparing the gelling behaviors under the four treatments (alkali-induced, AI; heat-induced, HI; alkali-heat-induced, AHI; and alkali-heat-induced in sequence, AHIS). We measured the secondary structure and investigated the changes in physicochemical properties, intermolecular forces, and water holding capacity (WHC) of the four gels during aging. The AHIS treatment improved the hardness and springiness of the gel; after 1 h of gel formation, the maximum value reached 754.22 ± 46.92 g and 0.96 ± 0.02, respectively. The WHC of the gels also presented a high level, with a maximum value of 88.40 ± 1.20% at 1 h. Although the HI gel had a high hardness value (957.32 ± 51.96 g), it exhibited the lowest elasticity value (0.68 ± 0.03) in 5 h. Meanwhile, the AI gel had low hardness (661.48 ± 32.43 g) and springiness (0.77 ± 0.03) in 5 h. A compact and regular microstructure was formed when the OVA solution was treated with AHIS, meanwhile, the free sulfhydryl (SH) and disulfide bonds (SS) and WHC of the AHIS gel did not change significantly (p > .05), which demonstrated that the gel had formed a stable gel system. Raman spectroscopy showed that AHIS treatment was beneficial to enhance the degree of cross-linking between proteins, the secondary structure changed considerably, the α-helix structure reduced, and the β-structure (β-sheet and β-turn) and random coil increased. Thus, this study provides a new approach to developing high-protein alkaline gel food.