Alkali-Induced Phenolic Acid Oxidation Enhanced Gelation of Ginkgo Seed Protein

Abstract

The effect of alkali-induced oxidation of three phenolic acids, namely gallic acid, epigallocatechin gallate, and tannic acid, on the structure and gelation of ginkgo seed protein isolate (GSPI) was investigated. A mixture of 12% (w/v) GSPI and different concentrations of alkali-treated phenolic acids (0, 0.06, 0.24, and 0.48% w/w) were heated at 90 °C, pH 6.0, for 30 min to form composite gels. The phenolic treatment decreased the hydrophobicity of the GSPI sol while enhancing their rheological properties. Despite a reduced protein solubility, water holding capacity, stiffness, and viscoelasticity of the gels were improved by the treatments. Among them, the modification effect of 0.24% (w/v) EGCG was the most prominent. Through the analysis of microstructure and composition, it was found to be due to the covalent addition, disulfide bond formation, etc., between the quinone derivatives of phenolic acids and the side chains of nucleophilic amino acids. Phenolic acid modification of GSPI may be a potential ingredient strategy in its processing.

L-Theanine Improves the Gelation of Ginkgo Seed Proteins at Different pH Levels

“…All gel samples displayed considerably higher G ′′ values than G ′ values, indicating a predominately elastic behavior for the GSPI gels. This finding aligns with our previous observation [42]. Protein molecules began to unfold when the denaturation temperature was reached.…”

“…The sols and gels were prepared according to our previous study with minor modifications [42]. The GSPI was dispersed in deionized water to prepare a 24% (w/v) sol.…”

“…The GSPI sols were diluted to 1 mg/mL using 50 mM citrate-phosphate buffer at the appropriate pH for intrinsic fluorescence determination. The intrinsic fluorescence was measured with emission wavelengths between 320 and 400 nm and an excitation wavelength of 295 nm using a scanning speed of 1 nm/s [42].…”

Mechanical Properties, Microstructure, and In Vitro Digestion of Transglutaminase-Crosslinked Whey Protein and Potato Protein Hydrolysate Composite Gels

“…The amide I band (1700-1600 cm −1 ) was the most sensitive region that could be used to interpret the protein secondary structure by multiple peak fi ing analysis [46]. The shift of the amide I band was related to the change in the protein secondary structure [45]. The complex protein ratios significantly affected the secondary structure of proteins in the gel, as shown in Figure 4B and Table S1.…”

“…This could be related to the interaction between the CH2 and CH3 groups. Inconsistently, Zhang et al [45] thought the change could be the stretching of CH2 and NH 3 +.…”