Relationship between Molecular Flexibility and Emulsifying Properties of Soy Protein Isolate-Glucose Conjugates

Abstract

At present, the structure−activity relationships of soy protein isolate are still not well understood. In this paper, the relationship between molecular flexibility and emulsifying properties of soy protein isolate and soy protein isolate−glucose conjugates were investigated. The Maillard reaction was carried out at different temperature conditions (50 °C, 60 °C, 70 °C, 80 °C, and 90 °C) under a specific wet condition. Meanwhile, structural properties including surface hydrophobicity (H 0 ), molecular flexibility and secondary, tertiary, quaternary structures, and the free sulfhydryl group (−SH) content were measured. The results showed that there was a good correlation between molecular flexibility and emulsifying properties, and the correlation coefficients was 0.920 (P < 0.01) for emulsifying activity and 0.952 (P < 0.01) for emulsion stability. Compared with soy protein isolate, the H 0 of samples at different temperatures first increased and then decreased reaching a maximum at 70 °C, a red shift occurred during the whole given reaction conditions shown by the intrinsic fluorescence spectrum, and the free sulfhydryl content also displayed a marked increase (P < 0.05). At the same time, the particle size gradually became smaller as the degree of grafting increased. The contents of β-turn and random coil increased at the cost of α-helix and β-sheet contents, as evidenced by Fourier transform infrared results. The findings could provide a deep insight into the structure−function relationship of soy protein isolate−glucose conjugates, thus providing theoretical guidance for further research of soy proteins.

Effects of Different Denaturants on Properties and Performance of Soy Protein-Based Adhesive

“…The hydrophobic fluorescent probe (ANS) binds to aromatic amino acids at an excitation wavelength of 390 nm and has a maximum absorption at 470 nm. The fluorescence intensity is proportional to the surface hydrophobicity of the protein [24]. Results for the first set of adhesive samples is presented in Figure 2.…”

Ultrasound-Assisted Mild Heating Treatment Improves the Emulsifying Properties of 11S Globulins

“…The flexibility of a protein structure regulates its surface activity and emulsification [39,40]. The molecular flexibility of a protein can be detected using the protease digestion method [41] and presented as the comparative motion of different structural intervals in proteins or the amino acid residue rearrangement rate in polypeptide chains [40]. Flexibilities of proteins performing the same catalytic activity seem to be about the same at their temperature optima.…”

“…The molecular flexibility of the protein extract was evaluated as previously described [41]. Briefly, 250 µL of 1.0 mg/mL (w/v) trypsin solution (0.05 mol/L Tris-HCl buffer solution, pH 8.0) was mixed with 4 mL of 1.0 mg/mL (w/v) protein solution at 37 • C. After 5 min of reaction, 4 mL of 5 mg/mL trichloroacetic acid (TCA) was added to the reaction solution to terminate the enzymatic reaction and precipitate the protein.…”

Miso Soup Consumption Enhances the Bioavailability of the Reduced Form of Supplemental Coenzyme Q10

“…e absorption of orally administered CoQ 10 is improved when emulsified with a surfactant that has a higher hydrophile-lipophile balance value [46]. Soy proteins have emulsifying and interfacial properties [47], and the amino-carbonyl reaction of soy proteins with sugar improves their emulsifying properties [48]. Some of the soy proteins in miso are modified by the amino-carbonyl reaction, which explains its brown color.…”