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The aim of the paper was to investigate the effect of ultrasonic emulsification treatment on the fabrication mechanism and stability of the emulsion. The covalent conjugate made with rice bran protein hydrolysate (RBPH) and ferulic acid (FA) was used as the emulsifier. The effects of high intensity ultrasound (HIU) power with different level (0 W, 150 W, 300 W, 450 W and 600 W) on the stability of emulsion were evaluated. The results showed that ultrasonic emulsification can significantly improve the stability of the emulsions (p < 0.05). The emulsion gained better stability and emulsifying property at 300 W. It was able to fabricate emulsion with smaller particle size, more uniform distribution and higher interfacial protein content. It was confirmed by fluorescent microscopy and cryo-scanning electron microscopy (cryo-SEM) furtherly. And it was also proved that the emulsion treated by proper HIU treatment at 300 W had better storage stability. Excessive HIU treatment (450 W, 600 W) had negative effects on the stability of emulsion. The stability of emulsion (300 W) against different environmental stresses was further explored, which established a theoretical basis for the industrial application of emulsion in food industry., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Rice bran protein hydrolysates (RBPH) pretreated with high hydrostatic pressure (HHP) covalently interacted with ferulic acid (FA) (0.5 to 2.5 mg/mL) under alkaline conditions. The structural and functional properties of the conjugates were investigated. The results revealed that the FA binding equivalent on RBPH increased from 6.03 to 207.64 nmol/mg. FTIR spectral analysis indicated that the content of α-helix increased, whereas the contents of β-sheet, β-turn, and random coil decreased. The surface hydrophobicity ( H 0 ) of RBPH increased, the fluorescence intensity decreased, and the tertiary structure changed because of covalent interactions between RBPH and FA. The emulsifying activity index of RBPH-FA (1.5 mg/mL) was 35.10% higher than that of the control, whereas FA concentrations higher than 1.5 mg/mL had a negative effect on emulsifying properties. RBPH-FA (2.5 mg/mL) exhibited the strongest antioxidant activity. This study provides a new reference for the application of RBPH-FA conjugates in food processing.

Rice bran protein (RBP) hydrolysis was conducted after high hydrostatic pressure (HHP) pretreatment. The structural and functional properties of HHP-pretreated rice bran protein hydrolysates (RBPH) were investigated. HHP pretreatments were conducted at 100, 200, and 300 MPa; then, enzymatic hydrolysis at atmospheric pressure was performed using trypsin. An RBPH sample that had not been pretreated by HHP was used as a control. Free sulfhydryl (SH) content, SDS-PAGE profiles, high-performance size exclusion chromatography (HPSEC), Fourier transform infrared (FTIR) spectrum, scanning electron microscopy (SEM), intrinsic fluorescence spectrum, solubility, and emulsifying and foaming properties were evaluated. Changes in particle size and ζ-potential were monitored. Compared with the control, the results of solubility, the emulsifying activity index (EAI) and the emulsifying stability index (ESI) increased significantly (p < 0.05) at 200 MPa. The content of free SH increased significantly (p < 0.05) at 100 MPa. FTIR spectrum and fluorescence analysis confirmed the changes in the secondary and tertiary structures. The experimental results indicated that the structural and functional properties of HHP-pretreated RBPH improved. [ABSTRACT FROM AUTHOR]

The effects of the addition of different anionic polysaccharides (gum arabic, pectin, xanthan gum and alginate) on the stability of a rice bran protein hydrolysate (RBPH)-stabilized emulsion were investigated. The type and concentration of the polysaccharide have substantial influence on the emulsion stability. Pectin and xanthan gum were better able to stabilize RBPH-coated droplets compared with gum arabic and alginate. Various environmental stresses (salt addition: 0–500 mM NaCl and pH 3.5; thermal processing: 30–90 °C 30 min, 0 mM NaCl, and pH 3.5) were used to test the stability of the emulsions stabilized with pectin or xanthan gum, and their apparent morphology, particle size, ζ-potential and microstructure were used as indicators of stability. The emulsions stabilized by xanthan gum or pectin were stable under all the tested NaCl concentrations. However, under the stress of thermal processing, the emulsion stabilized with xanthan gum shown instability at 90 °C. Polysaccharides improved the stability of the emulsions through increased electrostatic and steric repulsions between the droplets. These results could facilitate the application of rice bran protein as a food additive in the food industry. • Different anionic polysaccharides improve the stability of RBPH-stabilized emulsions. • Pectin and xanthan gum are better able to stabilize the RBPH-coated droplets. • Pectin- or xanthan gum-RBPH-stabilized emulsions can tolerate environmental stresses. [ABSTRACT FROM AUTHOR]

In this study, albumin and globulin were separated from rice bran and hydrolyzed with trypsin. The fractions of these proteins and their hydrolysates were comparatively studied to understand the mechanisms of the functional changes. SDS–PAGE showed that the molecular weights of the two hydrolysates decreased. In addition, the number of α-helices and random coils of the two proteins increased, which was consistent with the structure observed by SEM. Oil-in-water emulsions were prepared from the hydrolysate of rice bran albumin and globulin, and their ability to resist environmental pressure (pH: 3–9; salt addition: 0–300 mM NaCl and thermal processing: 30–90 °C for 30 min) and stability were evaluated. In an acidic environment, the emulsion formed by globulin hydrolysate had a smaller particle size and higher absolute ζ-potential values. Due to electrostatic repulsion, the emulsions formed by the two hydrolysates were not stable under high salt conditions. Temperature had no significant effect on the ζ-potential of the emulsions formed by the two hydrolysates, although the particle size increased significantly when the temperature was higher than 50 °C. In contrast, the emulsion stabilized by globulin hydrolysate was more stable. • Hydrolysis could improve the functional properties and increase the flexibility of RBA and RBG. • The emulsions stabilized by RBAH and RBGH had good thermal stability, but weak ionic stability. • Compared with RBAH, RBGH had better storage stability. [ABSTRACT FROM AUTHOR]