Impact of Microwave Time on the Structure and Functional Properties of Glycosylated Soy 7S Globulins

Abstract

This study examined the effects of varying microwave treatment durations (0-120 s) on the structural and functional properties of glycosylated soybean 7S protein. The results indicated that microwaving for 60 s significantly altered the structure of 7S, resulting in a more ordered protein configuration. The treated protein exhibited the largest particle size (152.3 nm), lowest polydispersity index (0.248), highest α-helix content (47.86%), and lowest β-sheet, β-turn, and random coil contents (12.33%, 16.07%, and 22.41%, respectively). It also showed the lowest endogenous fluorescence and surface hydrophobicity, and the highest thermal denaturation temperature (76.8 °C). Additionally, microwaving for ≤90 s led to increased peptide modifications, with carbamylation and deamidation being the most prevalent. A microwave treatment time of 60 s also notably enhanced the functional properties of glycosylated soybean 7S protein, optimizing water-holding capacity (6.060 g/g), emulsification activity, and stability (45.191 m²/g and 33.63 min). The foaming capacity was second only to the 120 s treatment (32% at 60 s versus 34% at 120 s), though the oil-holding capacity (22.73 g/g) and foaming stability (33.42%) were significantly lower than those of the controls. Microwave treatment durations exceeding or below 60 s led to the structural disintegration of the protein, diminishing most of its functional properties. This study explores the mechanism of how microwave processing time affects the structure and functional properties of glycosylated soybean 7S protein and identifies 60 s as the optimal microwave processing time. It meets the demands for healthy and delicious food in home cooking, providing scientific evidence for using microwave processing technology to enhance the nutritional value and quality of food.

Keywords: food industry; functional properties; glycosylation; microwave heating; soy 7S globulin; structural properties.

Figure 1

The effect of varying microwave treatment times on the microstructure of glycosylated soybean 7S proteins is illustrated in images (A–E), which correspond to treatment durations of 0, 30, 60, 90, and 120 s, respectively.

Figure 2

The effect of varying microwave treatment times on the particle size and polydispersity index (PDI) of glycosylated soybean 7S proteins is shown; The different letters in the figure indicate significant differences between the groups (p < 0.05).

Figure 3

The effect of varying microwave treatment durations on the secondary structure (a) and percentage composition (b) of glycosylated 7S protein.

Figure 4

Analysis of far-ultraviolet CD spectra of glycosylated soybean 7S protein subjected to varying durations of microwave treatment.

Figure 5

The impact of varying microwave exposure durations on the tryptophan fluorescence spectra of glycosylated soybean 7S protein.

Figure 6

Exogenous fluorescence of glycosylated soybean 7S proteins subjected to varying microwave treatment durations.

Figure 7

Effect of various microwave durations on the DSC curves of glycosylated soybean 7S proteins.

Figure 8

Relative quantification of amino acid residue-modified peptides in glycosylated soybean 7S protein under varying microwave treatment durations.

Figure 9

Major types of modifications in glycosylated soybean 7S proteins, both major and minor, at varying microwave durations.

Figure 10

Water-holding (a) and oil-holding (b) properties of glycosylated soybean 7S at different microwave times; the different letters in the figure indicate significant differences between the groups (p < 0.05).

Figure 11

Emulsifiability and emulsion stability of glycosylated soybean 7S under varying microwave treatment durations; the different letters in the figure indicate significant differences between the groups (p < 0.05).

Figure 12

Foamability and stability of glycosylated soybean 7S proteins under varying microwave durations; the different letters in the figure indicate significant differences between the groups (p < 0.05).