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.

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Phytosterols are bioactive components capable of reducing the level of cholesterol in serum. In this study, phytosterol acetic ester (PA), phytosterol oleate ester (PO) and phytosterol linoleic ester (PL) were synthesized from phytosterol (PS) and organic acid to improve the solubility of phytosterols in oil. The purities of PA, PO and PL were 98.4, 95.9 and 95.7%, respectively. Caco-2 cell monolayers and Wistar rats were used to research the bioavailability of synthesized esters (PE) in vitro and in vivo. Experiments using the Caco-2 cell monolayer model showed that the transport mechanism of phytosterol esters was passive transport. Experiments in vivo showed that the PS content in rat blood reached the highest level at 3 h, with a value of 21.82 μg/mL. PS content in the liver was the highest at 3 h, with a value of 43.65 μg/g. Bioavailability of PL is the highest, reaching a value as high as 19.57%. Acute study in the rats showed that the PS concentration in blood was at the safe level, and it had no side effects for health. In conclusion, the bioavailability of PL and PO is better than PS, PL and PO have more advantages in application.