Thermal Stability Improvement of Rice Bran Albumin Protein Incorporated with Epigallocatechin Gallate

Abstract

Rice bran albumin protein (RAP) is sensitive to thermal changes and tends to degrade when exposed to high-temperature processing. In this work, RAP-epigallocatechin-3-gallate (EGCG) complex (RAPE) was prepared and the thermal stability was evaluated. Fluorescence results showed that EGCG could interact with RAP with a binding number n of 0.0885:1 (EGCG:RAP, w/w) and a binding constant K of 1.02 (± 0.002) ×10 /M, suggesting both hydrogen bonding and van der Waals forces played an important role. FTIR analysis demonstrated that EGCG could induce secondary structural changes in RAP above a ratio of 1.6:1 (EGCG:RAP, w/w). Interestingly, the secondary structure changes of RAPE at different temperatures (25, 50, 60, 70, and 80 °C) were inhibited compared with that for RAP, suggesting RAPE was more resistant and stable to the heat treatment. In addition, a dense porous structure of RAPE was achieved due to the EGCG binding after thermal treatment. Furthermore, the T temperature of RAPE increased significantly from 64.58 to 74.16 °C and the enthalpy also increased from 85.53 to 138.52 J/g with a mass ratio increasing from 0 to 3.2 (EGCG:RAP, w/w), demonstrating the thermal stability of RAPE. In addition, the valine, methionine, and lysine content in RAPE were significantly higher than RAP following 80 °C treatment for 20 min (P < 0.05), exhibiting enhanced amino acid profiles, which might be due to EGCG-RAP interactions and microenvironment changes around relevant amino acids. These findings demonstrate that EGCG has the potential to improve the thermal stability of sensitive proteins and is beneficial for usage in the food industry.

Gel properties of transglutaminase‐induced soy protein isolate–polyphenol complex: influence of epigallocatechin‐3‐gallate

“…In addition, the binding constant K of EGCG to SPI was 0.15 ± 0.001 × 10 3 L mol −1 (Fig. 1(C)), which was comparable to that reported previously, and indicated low affinity (10 3 –10 4 L mol −1 ) associated with hydrogen bonding, hydrophobic bonding and van der Waals forces 12,17 . These results suggest that EGCG molecules are bound to thermally induced SPI primarily via hydrogen bonding, hydrophobic bonding and van der Waals forces.…”

“…In addition, with an increase in EGCG concentration, the fluorescence intensity of thermally induced SPI decreased significantly ( P < 0.05), suggesting that the microenvironment around Trp was altered by binding of EGCG to thermally induced SPI. According to the established model, 12,17,18 the binding site number n of EGCG to thermally induced SPI obtained using model fitting was 0.0634:1 (EGCG:SPI, w/w), indicating that approximately 0.0634 of the EGCG mass was attached to a thermally induced SPI molecule. In addition, the binding constant K of EGCG to SPI was 0.15 ± 0.001 × 10 3 L mol −1 (Fig.…”

“…Trp intrinsic emission fluorescence spectra of SPIE ((0–0.20, EGCG:SPI, w/w; SPI (1 g L −1 ) in pH 7.0 deionized water; at 25 °C)) were determined using an RF‐5301PC fluorescence spectrophotometer (Shimadzu Inc., Kyoto, Japan), with an excitation wavelength of 290 nm and an emission wavelength between 300 and 500 nm. To determine the stoichiometry and binding constant, the intensity data were fitted to the following equation for the binding of EGCG to an independent binding site on the protein according to previously described methods: 12,17,18 …”

“…Meanwhile, thermally induced protein‐based nanocomplexes have been shown to serve as outstanding delivery systems for food polyphenols such as EGCG and curcumin, as they can improve the stability, taste and bioaccessibility of the encapsulated bioactives 8–10 . Concurrently, the polyphenols may be bound to proteins via hydrophobic and hydrogen bonding, thereby altering protein surface hydrophobicity and structure, and subsequently changing their functional characteristics 8,9,11,12 . Hence EGCG may effectively function to alter the surface hydrophobicity of SPI to improve its gelation rate and form a more uniform network structure, while thermally induced SPI could serve as a vehicle to protect the biological activity of EGCG and dramatically suppress its associated bitterness and astringency.…”

Self-Assembly of Protein Nanoparticles from Rice Bran Waste and Their Use as Delivery System for Curcumin

“…As an abundant and cheap agricultural byproduct, rice bran protein has many desirable nutritional factors, such as hypoallergenic, antioxidant, anticancer, and significant quantities of essential amino acids, which can be a useful supplement of proteins in milk and soy infant formulations. 4 Rice bran protein compositions include 37% albumins, 36% globulins, 22% glutelins, and 5% prolamins. 5 Among these proteins, rice bran albumin (RBA) exhibits high solubility in water with the beneficial properties of less allergenic properties, nontoxic, lowcost, biodegradability, and biocompatibility.…”