In vitro gastrointestinal digest of catechin-modified β-conglycinin oxidized by lipoxygenase-catalyzed linoleic acid peroxidation

Role of sodium pyrophosphate and catechin in the enzymatic hydrolysis of oxidatively damaged myofibrillar protein gels in vitro: Mechanistic insights

This study investigated the effects of sodium pyrophosphate (SPP) and catechin (C) on the in vitro enzymatic digestion of oxidatively damaged myofibrillar protein (MP) gel. The results indicated that SPP increased the β-sheet content and the gastric digestibility of the MP gel, while C hindered the transition from α-helix to β-sheet structure, leading to decreased digestibility. Notably, neither compound significantly affected intestinal digestibility. Furthermore, SPP and C significantly enhanced the antioxidant activity of MP gel digestion products. Notably, their synergistic hydrolysis products, simulating both gastric and gastrointestinal stages, chelated 91.4 % and 89.1 % of Fe2+ and scavenged 59.4 % and 77.6 % of hydroxyl radicals, respectively. Moreover, the final digestion products of the MP gel treated with SPP and C exhibited the highest content of negatively charged amino acids and absolute Zeta potential values. Overall, this study demonstrated that incorporating SPP and C could positively impact the digestion of oxidatively damaged MP gels.

Effects of Baking and Frying on the Protein Oxidation of Wheat Dough

Protein oxidation caused by food processing is harmful to human health. A large number of studies have focused on the effects of hot processing on protein oxidation of meat products. As an important protein source for human beings, the effects of hot processing on protein oxidation in flour products are also worthy of further study. This study investigated the influences on the protein oxidation of wheat dough under baking (0-30 min, 200 °C or 20 min, 80-230 °C) and frying (0-18 min, 180 °C or 10 min, 140-200 °C). With the increase in baking and frying time and temperature, we found that the color of the dough deepened, the secondary structure of the protein changed from α-helix to β-sheet and β-turn, the content of carbonyl and advanced glycation end products (AGEs) increased, and the content of free sulfhydryl (SH) and free amino groups decreased. Furthermore, baking and frying resulted in a decrease in some special amino acid components in the dough, and an increase in the content of amino acid oxidation products, dityrosine, kynurenine, and N'-formylkynurenine. Moreover, the nutritional value evaluation results showed that excessive baking and frying reduced the free radical scavenging rate and digestibility of the dough. These results suggest that frying and baking can cause protein oxidation in the dough, resulting in the accumulation of protein oxidation products and decreased nutritional value. Therefore, it is necessary to reduce excessive processing or take reasonable intervention measures to reduce the effects of thermal processing on protein oxidation of flour products.

Potential implications of oxidative modification on dietary protein nutritional value: A review

During food processing and storage, proteins are sensitive to oxidative modification, changing the structural characteristics and functional properties. Recently, the impact of dietary protein oxidation on body health has drawn increasing attention. However, few reviews summarized and highlighted the impact of oxidative modification on the nutritional value of dietary proteins and related mechanisms. Therefore, this review seeks to give an updated discussion of the effects of oxidative modification on the structural characteristics and nutritional value of dietary proteins, and elucidate the interaction with gut microbiota, intestinal tissues, and organs. Additionally, the specific mechanisms related to pathological conditions are also characterized. Dietary protein oxidation during food processing and storage change protein structure, which further influences the in vitro digestion properties of proteins. In vivo research demonstrates that oxidized dietary proteins threaten body health via complicated pathways and affect the intestinal microenvironment via gut microbiota, metabolites, and intestinal morphology. This review highlights the influence of oxidative modification on the nutritional value of dietary proteins based on organs and the intestinal tract, and illustrates the necessity of appropriate experimental design for comprehensively exploring the health consequences of oxidized dietary proteins.

Effects of ultrasonic pretreatment of soybean protein isolate on the binding efficiency, structural changes, and bioavailability of a protein-luteolin nanodelivery system

The combination of protein and flavonoids can ameliorate the problems of poor solubility and stability of flavonoids in utilization. In this study, soybean protein isolate pretreated by ultrasonication was selected as the embedding wall material, which was combined with luteolin to form a soybean protein isolate-luteolin nanodelivery system. The complexation effect and structural changes of soybean protein isolate (SPI) and ultrasonic pretreatment (100 W, 200 W, 300 W, 400 W and 500 W) of soybean protein isolate with luteolin (LUT) were compared, as well as the changes in digestion characteristics and antioxidant activity in vitro. The results showed that proper ultrasonic pretreatment increased the encapsulation efficacy, loading amount and solubility to 89.72%, 2.51 μg/mg and 90.56%. Appropriate ultrasonic pretreatment could make the particle size and the absolute value of ζ-potential of SPI-LUT nanodelivery system decrease and increase respectively. The FTIR and fluorescence results show that appropriate ultrasonic pretreatment could reduce α-helix, β-sheet and random coil, increase β-turn, and enhance fluorescence quenching. The thermodynamic evaluation results indicate that the ΔG < 0, ΔH > 0 and ΔS > 0, so the interaction of LUT with the protein was spontaneous and mostly governed by hydrophobic interactions. The XRD results show that the LUT was amorphous and completely wrapped by SPI. The DSC results showed that ultrasonic pretreatment could improve the thermal stability of SPI-LUT nanodelivery system to 112.66 ± 1.69 °C. Digestion and antioxidant analysis showed that appropriate ultrasonic pretreatment increased the LUT release rate and DPPH clearance rate of SPI-LUT nanodelivery system to 89.40 % and 55.63 % respectively. This study is a preliminary source for the construction of an SPI nanodelivery system with ultrasound pretreatment and the deep processing and utilization of fat-soluble active substances.

Effects of Peroxyl Radicals on the Structural Characteristics and Fatty Acid Composition of High-Density Lipoprotein from Duck Egg Yolk

In this study, high-density lipoprotein (HDL) from duck egg yolk was subjected to oxidation with a system based on 2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH)-derived peroxyl radicals. The effects of peroxyl radicals on the protein carbonyl, free sulfhydryl, secondary/tertiary structure, surface hydrophobicity, solubility, particle size distribution, zeta potential and fatty acid composition of HDL were investigated by using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), Fourier-transform infrared spectroscopy (FTIR), circular dichroism (CD), fluorescence spectroscopy, dynamic light scattering and ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). The results indicated that the content of protein carbonyl was significantly increased, that of free sulfhydryl was obviously reduced, and the ordered secondary structure was also decreased with increasing AAPH concentration. In addition, the surface hydrophobicity and solubility of HDL showed apparent increases due to the exposure of hydrophobic groups and aggregation of protein caused by oxidation. The fatty acid composition of HDL exhibited pronounced changes due to the disrupted protein–lipid interaction and lipid oxidation by AAPH-derived peroxyl radicals. These results may help to elucidate the molecular mechanism for the effect of lipid oxidation products on the oxidation of duck yolk proteins.

Non-covalent interaction of soy protein isolate and catechin: Mechanism and effects on protein conformation

Understanding the molecular mechanism behind protein-polyphenol interactions is critical for the application of protein-polyphenol compounds in foods. The purpose of this research was to investigate the non-covalent interaction mechanism between soy protein isolate (SPI) and catechin and its effect on protein conformation. We observed that particle size, ζ-potential, and polyphenol bound equivalents of SPI increased significantly after non-covalent modification with catechin. These changes caused SPI to aggregate and form a network-like structure. Fourier transform infrared spectroscopy (FTIR) indicated that increased catechin concentrations caused SPI to become looser and more disordered as its α-helix and β-sheet transformed into β-turn and random coil. Furthermore, internal structure of SPI was opened and its hydrophobic groups were exposed to a polar environment, which was demonstrated by decreased surface hydrophobicity. Thermodynamic analysis and molecular docking results showed that the main forces present between SPI and catechin were hydrophobic interactions and hydrogen bonds.

Non-covalent interaction between pea protein isolate and catechin: effects on protein structure and functional properties

The aim of this study was to investigate the effects of non-covalent interaction between pea protein isolate (PPI) and different concentrations (0.05–0.25%, w/v) of catechin (CT) on the structural and functional characteristics of protein.

Metabolomics reveals the impact of saturation of dietary lipids on aging and longevity of C. elegans

Saturation differences in dietary lipids modify their digestive and absorption profiles, endpoints that may influence the nutrition and health. This study tests the hypothesis that dietary with elevated unsaturated fats...

Preparation of Pickering emulsion based on soy protein isolate-gallic acid with outstanding antioxidation and antimicrobial

This study investigated a novel antioxidant and antimicrobial Pickering emulsion stabilized by soy protein isolate (SPI) and gallic acid (GA) as an excellent protective delivery medium for lipophilic functional food. SPI-GA complex nanoparticles were fabricated by a covalent cross-linking mechanism under alkaline conditions with a small particle size (42.93-24.91 nm) and high zeta potential (26.92-38.58 -mV), which led to improved stability at high GA concentrations. Without the addition of preservatives, it was found that SPI-GA complex nanoparticles have a certain antimicrobial ability. Using these nanoparticles as the only stabilizers, outstanding antioxidant and antimicrobial Pickering emulsions could be easily prepared, and they had a small droplet size (948.09-457.82 nm), great stability and inhibited lipid peroxidation and antibacterial ability. Oxidation and microbial protection proceeded in a GA concentration-dependent manner. This study provides a novel way to prepare functionalized Pickering emulsions as delivery media for functional lipophilic raw materials.

Soy Protein: Molecular Structure Revisited and Recent Advances in Processing Technologies

Rising health concerns and increasing obesity levels in human society have led some consumers to cut back on animal protein consumption and switch to plant-based proteins as an alternative. Soy protein is a versatile protein supplement and contains well-balanced amino acids, making it comparable to animal protein. With sufficient processing and modification, the quality of soy protein can be improved above that of animal-derived proteins, if desired. The modern food industry is undergoing a dynamic change, with advanced processing technologies that can produce a multitude of foods and ingredients with functional properties from soy proteins, providing consumers with a wide variety of foods. This review highlights recent progress in soy protein processing technologies. Using the current literature, the processing-induced structural changes in soy protein are also explored. Furthermore, the molecular structure of soy protein, particularly the crystal structures of β-conglycinin and glycinin, is comprehensively revisited.

Proteins from leguminous plants: from structure, property to the function in encapsulation/binding and delivery of bioactive compounds

Leguminous proteins are important nutritional components in leguminous plants, and they have different structures and functions depending on their sources. Due to their specific structures and physicochemical properties, leguminous proteins have received much attention in food and nutritional applications, and they can be applied as various carriers for binding/encapsulation and delivery of food bioactive compounds. In this review, we systematically summarize the different structures and functional properties of several leguminous proteins which can be classified as ferritin, trypsin inhibitor, β-conglycinin, glycinin, and various leguminous proteins isolates. Moreover, we review the development of leguminous proteins as carriers of food bioactive compounds, and emphasize the functions of leguminous protein-based binding/encapsulation and delivery in overcoming the low bioavailability, instability and low absorption efficiency of food bioactive compounds. The limitations and challenges of the utilization of leguminous proteins as carriers of food bioactive compounds are also discussed. Possible approaches to resolve the limitations of applying leguminous proteins such as instability of proteins and poor absorption of bioactive compounds are recommended.

Catechins as Model Bioactive Compounds for Biomedical Applications

Research regarding polyphenols has gained prominence over the years because of their potential as pharmacological nutrients. Most polyphenols are flavanols, commonly known as catechins, which are present in high amounts in green tea. Catechins are promising candidates in the field of biomedicine. The health benefits of catechins, notably their antioxidant effects, are related to their chemical structure and the total number of hydroxyl groups. In addition, catechins possess strong activities against several pathogens, including bacteria, viruses, parasites, and fungi. One major limitation of these compounds is low bioavailability. Catechins are poorly absorbed by intestinal barriers. Some protective mechanisms may be required to maintain or even increase the stability and bioavailability of these molecules within living organisms. Moreover, novel delivery systems, such as scaffolds, fibers, sponges, and capsules, have been proposed. This review focuses on the unique structures and bioactive properties of catechins and their role in inflammatory responses as well as provides a perspective on their use in future human health applications.

ω-6 Polyunsaturated fatty acids (linoleic acid) activate both autophagy and antioxidation in a synergistic feedback loop via TOR-dependent and TOR-independent signaling pathways

ω-6 Polyunsaturated fatty acids (PUFAs) are essential fatty acids that participate in macroautophagy (hereafter referred to as autophagy) and the Kelch ECH-associating protein 1 (Keap1)—nuclear factor erythroid 2-related factor 2 (Nrf2) antioxidant system in organisms. However, the molecular mechanisms by which ω-6 PUFAs (linoleic acid) regulate autophagy and Keap1–Nrf2 antioxidant system are not completely understood. Therefore, the purposes of this study were to explore the molecular mechanisms by which ω-6 PUFAs (linoleic acid) regulate autophagy and antioxidant system and to investigate the potential relationship between autophagy and antioxidant system through transcriptomic analysis, quantitative real-time polymerase chain reaction (RT-qPCR), western blot analysis, coimmunoprecipitation (Co-IP) and electrophoretic mobility shift assays (EMSAs) in vivo and in vitro. The results of the present study indicated that ω-6 PUFAs in diets induced autophagy but decrease antioxidant ability in vivo. However, the results also provided evidence, for the first time, that ω-6 PUFAs (linoleic acid) induced autophagy and increased antioxidant ability through the adenosine monophosphate-activated protein kinase (AMPK) signaling pathway and the AMPK-target of rapamycin (TOR) signaling pathway in hepatocytes in vitro. Interestingly, the findings revealed a ω-6 PUFA-induced synergistic feedback loop between autophagy and antioxidant system, which are connected with each other through the P62 and Keap1 complex. These results suggested that ω-6 PUFAs (linoleic acid) could be useful for activating a synergistic feedback loop between autophagy and antioxidant system and could greatly aid in the prevention and treatment of multiple pathologies.

Impact of a novel partial defatting technology on oxidative stability and sensory properties of peanut kernels

A novel process, 'mechanical expression preserving shape integrity', was conceived to prepare low-fat peanuts in response to health-conscious consumer demands. The main purpose of this study was to preserve the taste, aroma, and oxidative stability of the defatted product. Results generated from a central composite rotatable design showed that highest consumer sensory scores were reached at low pressures (4-6 MPa). Free fatty acid, peroxide, p-anisidine, and total oxidation values were mostly affected by water content [W] and pressure [P] with high correlation coefficients (82% < R² < 87%). Overall, lipid oxidation and flavor fade were associated with higher defatting ratios and greater physical damage. The latter plays a major role in increasing the surface area and facilitating the access of oxygen to the remaining oil, thus rendering the defatted product more prone to oxidation. However, oxidation was reduced significantly using a Response Surface Methodology to optimize conditions ([W] 12.2 ± 0.6%d.b., [P] 6 ± 0.3 MPa and time [t] 18.2 ± 0.6 min).