Nutrients in rice bran oil and their nutritional functions: a review.

Rice is an important food crop throughout the world. Rice bran, the outer layer of rice grain, is a by-product generated during the rice milling process. Rice bran oil (RBO) is extracted from rice bran and has also become increasingly popular. RBO is considered to be one of the healthiest cooking oils due to its balanced proportion of fatty acids, as well as high content of γ-oryzanol together with phytosterols, vitamin E, wax ester, trace and macro elements, carotenoids, and phenolics. The existence of these compounds provides RBO with various functions, including hypotensive and hypolipidemic functions, antioxidant, anticancer, and immunomodulatory functions, antidiabetic function, anti-inflammatory and anti-allergenic functions, hepatoprotective activity function, and in preventing neurological diseases. Recently, research on the nutrients in RBO focused on the detection of nutrients, functions, and processing methods. However, the processing and utilization of rice bran remain sufficiently ineffective, and the processing steps will also affect the nutrients in RBO to different degrees. Therefore, this review focuses on the contents and nutritional functions of different nutrients in RBO and the possible effects of processing methods on nutrients.

MOF-derived nanozyme CuOx@C and its application for cascade colorimetric detection of phytosterols.

Phytosterols (PSs), a class of naturally occurring bioactive lipid compounds, have been found to possess a significant cholesterol-lowering effect. In developing countries, the consumption of rapeseed oil is the primary pathway of PS intake for the general population. However, developing low-cost, real-time, and high-throughput screening techniques for PSs remains a challenge. Here, a Cu-based nanocomposite CuOx@C was synthesized via a simple method of the calcination of HKUST-1 and systematically characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The CuOx@C demonstrated excellent peroxidase-like (POD-like) activity, functioning as a peroxidase mimic to facilitate the catalysis of 3,3',5,5'-tetramethylbenzidine (TMB) into its oxidized form (oxTMB), thereby initiating a discernible color response. On the basis of this discovery, a CuOx@C-based colorimetric method for detecting total sterols in rapeseed was successfully constructed via cascade reactions. After optimizing the conditions, the high-throughput screening of total sterols in rapeseed could be completed in only 21 min, which significantly facilitated the sensing of PSs. A linear range of 0.6-6 mg/g was achieved for the detection of total sterols in rapeseed samples, thereby satisfying the requirements for detection. In addition, due to the high stability of CuOx@C and the specificity of cholesterol oxidase, the developed method had excellent stability and selectivity toward PSs, indicating that this work has huge prospects for commercial application. This innovative work overcomes the limitation of the instrumental method and provides a portable and reliable tool for total sterols detection. It can also facilitate the development of oilseeds with a high content of PSs.

Contributions of Common Foods to Resveratrol Intake in the Chinese Diet.

Resveratrol is a polyphenolic compound with antioxidant and anti-inflammatory properties and therefore has potential health benefits for the prevention and treatment of a wide range of diseases, including cardiovascular disease, cancer, diabetes, and neurodegenerative diseases. The beneficial dose of resveratrol is between 30 and 150 mg. Although the health benefits of resveratrol have been extensively studied, resveratrol intake through the diet of residents in China remains unclear, which restricts the development of resveratrol-rich foods. In this study, a dietary assessment was conducted to reveal that the daily resveratrol intake by Chinese residents through common foods was only 0.783 mg, which was significantly below the beneficial dose. Among the main food types, fruits emerged as the primary source of resveratrol, contributing to 88.35% of the total intake. To improve resveratrol intake, potential methods to increase its consumption were proposed. First method is to increase the resveratrol content of fruits and peanuts. In addition, resveratrol can be extracted from peels. It is also recommended to adopt technical means to improve the bioavailability of resveratrol and develop related supplements and functional drinks.

Peptidomic analysis of digested products of surimi gels with different degrees of cross-linking: In vitro gastrointestinal digestion and absorption.

To investigate the cross-linking degree on the in vitro gastrointestinal digestion and absorption properties of surimi gel, three types of surimi gels with low, moderate, and high cross-linking degrees were prepared, and then in vitro digestion models (static and dynamic) and a Caco-2 cell monolayer model combined with LC-MS/MS were used to do peptidomic analysis of digestive and absorbed juices. The results showed that an increase in cross-linking degree promoted the release of peptides after gastrointestinal digestion. These peptides originated from the myosin head and rod, the rod was the main digestion region. More potential bioactive peptides from intestinal digestive juice could be transported through the intestinal epithelium. Compared with static digestion, dynamic digestion digested surimi gels more thoroughly, especially during gastric digestion. This study provides a theoretical basis and guidance for the production of surimi products with higher nutritional value and the in vitro digestion methods of gelatinous foods.

In vitro trypsin digestion and identification of possible cross-linking sites induced by transglutaminase (TGase) of silver carp (Hypophthalmichthys molitrix) surimi gels with different degrees of cross-linking.

Surimi gels with different cross-linking degrees (18.52%, 34.67%, 62.87% and 79.11%) were prepared to identify the numbers and locations of lysine residues involved in TGase-induced cross-linking, and to reveal the quantity and location relationships among cross-linking degrees, cross-linking sites and digestion sites by using trypsin digestion, SDS-PAGE and LC-MS/MS methods. The results showed that with the increase in cross-linking degree from 18.52% to 79.11%, 1) the quantity of cross-linking sites gradually increased from 25 sites to 47 sites, 2) the main possible cross-linking domain moved from myosin head to rod, 3) the numbers of digestion sites first decreased from 1262 sites to 1194 sites, and then increased to 1302 sites, 4) the changes in the values of digestion sites were mainly concentrated in myosin rod and it was also the main region of digestion. This study can help exploring the relationship between enzymatic cross-linking and nutritional properties of food.

Proteomic profiling and oxidation site analysis of gaseous ozone oxidized myosin from silver carp (Hypophthalmichthys molitrix) with different oxidation degrees.

Ozone is used to in surimi production and affects the conformation of myosin and gelling properties. Amino acid analysis, SDS-PAGE, in-gel trypsin hydrolysis and LC-MS/MS were used to investigate the effect of the ozone treatment time on the oxidation principle of amino acids to identify the oxidation site and oxidation mechanism of myosin with different oxidation degrees. The results showed that the order of ozonation of amino acids from easy to difficult was tyrosine > cysteine > histidine > proline. The protein structure near the SH1-SH2 region initially changed when the ozone treatment time was 50 s. Prolonging the oxidation to 80 s leads to an irregular distribution of oxidation sites. Ten min of ozone treatment resulted in the aggregation from the SH1 helical region and myosin rod. This study helped to clarify the mechanism of ozone oxidation, thus providing a theoretical basis for producing surimi products of improved quality.

In Vitro Pepsin Digestion Characteristics of Silver Carp (Hypophthalmichthys molitrix) Surimi Gels with Different Degrees of Cross-Linking Induced by Setting Time and Microbial Transglutaminase.

Surimi gels are favored for their abundant proteins and unique taste. In this study, the pepsin digestion behaviors of surimi gels with different degrees of cross-linking induced by microbial transglutaminase (MTGase) and different setting times were investigated. For gels without (CK group) and with (TG group) MTGase, the slowest digestion rate (tM/2 = 20.13 and 79.19 min for CK and TG group, respectively), the least amino acid concentration (5.32 and 3.73 µmol/mL for CK and TG group, respectively), and the peptide amounts (1355 and 1788 for CK and TG group, respectively) were obtained at a moderate setting time (1-4 h) with the finest microstructure. However, the excessive setting time (8-12 h) formed an inhomogenous network, which accelerated the hydrolysis of gel proteins (tM/2 = 9.40 and 52.33 min for CK and TG group, respectively) and produced more amino acids (6.63 and 5.15 µmol/mL for CK and TG group, respectively) and peptide amounts (1644 and 2143 for CK and TG group, respectively). The above results also demonstrated that the presence of MTGase strengthened the compactness of gels as well as slowed down the digestion process with the release of less amino acids but more peptides. A large proportion of unique peptides were from the tail domain of myosin heavy chain. The discrepancy in bioactive peptides between different gels might be reduced in the subsequent intestinal digestion according to the in silico methods, demonstrating the diminished difference in the gastrointestinal digestion process in the aspect of releasing functional peptides. This study provides the theoretical basis and guideline in the field of gelation food digestion and surimi food industry to produce healthier surimi-based food.