Enhanced emulsification performance and interfacial properties of Janus-like rapeseed cruciferin through asymmetric acylation modification.

Plant protein emulsifiers, particularly rapeseed protein isolate with its superior amino acid composition and predominantly globular protein, have captured significant interest in the food industry. Nonetheless, the application of these proteins has been stymied by their lackluster emulsification properties. Addressing this challenge, our study implements an innovative asymmetric acylation technique to modify the surface of rapeseed cruciferin (RC), morphing it into a structure resembling Janus nanoparticles. This alteration amplifies the emulsification prowess of RC by a remarkable 2.7 times compared to its natural form, and 1.43 times over its conventionally acylated counterpart. The asymmetrically acylated RC, marked by a distinctive three-phase contact angle of 90.4°, manifests an outstanding amphiphilic character. Moreover, it surpasses both the natural and conventionally acylated RC in terms of diffusion, penetration, and rearrangement rates, as well as protein concentration at the oil-water interface. Compared to commonly used emulsifiers in the food industry, such as lecithin and soy protein, the asymmetrically acylated RC stands out, stabilizing emulsions with the tiniest particle size and effectively staving off emulsion stratification over a longer duration. This study underscores that asymmetric acylation serves as a reliable methodology for producing efficient plant protein emulsifiers, considerably amplifying their utility in the food industry.

Impact of exopolysaccharides-producing lactic acid bacteria on the chemical, rheological properties of buckwheat sourdough and the quality of buckwheat bread.

Exopolysaccharides (EPS) produced in situ by lactic acid bacteria (LAB) during sourdough fermentation have the potential to replace hydrocolloids in gluten-free sourdoughs. This study investigated effects of an EPS-producing Weissella cibaria NC516.11 fermentation on chemical, rheological properties of sourdough and the quality of buckwheat bread. Results indicate that the buckwheat sourdough fermentation by W. cibaria NC516.11 had lower pH (4.47) and higher total titrable acidity (8.36 mL) compared with other groups, and the polysaccharide content reached 3.10 ± 0.16 g/kg. W. cibaria NC516.11 can significantly improve the rheological properties and viscoelastic properties of sourdough. Compared with control group, the baking loss of NC516.11 group bread decreased by 19.94%, specific volume increased by 26.03%, and showed good appearance and cross-sectional morphology. Scanning electron micrograph revealed an intact and less porous cell structure. Meanwhile, W. cibaria NC516.11 significantly improved the texture of the bread and reduced the hardness and moisture loss during storage.

Study on the hypolipidemic activity of rapeseed protein-derived peptides.

Hyperlipidaemia, a common chronic disease, is the cause of cardiovascular diseases such as myocardial infarction and atherosclerosis. Generally, drugs for lowering blood lipids have disadvantages such as short or poor efficacy, high toxicity, and side effects. Rapeseed active peptides are excellent substitutes for lipid-lowering drugs because of their high biological safety, strong penetration, and easy absorption by the human body. This study separated and purified the rapeseed peptides using gel chromatography and mass spectrometry. Rapeseed peptides amino acid sequences were determined to obtain Glu-Phe-Leu-Glu-Leu-Leu (EFLELL) peptides with good hypolipidaemic activity and IC50 values of 0.1973 ± 0.05 mM (sodium taurocholate), 0.375 ± 0.03 mM (sodium cholate), and 0.203 ± 0.06 mM (sodium glycine cholate). The EFLELL hypolipidaemic activity was evaluated, and its mechanism of action was investigated using cell lines. Rapeseed peptide treatment significantly decreased the total cholesterol (T-CHO), triglyceride (TG), and low-density lipoprotein cholesterol (LDL-C) levels, and the protein and gene expression levels of proprotein convertase subtilisin/kexin type 9 (PCSK9) and low-density lipoprotein cholesterol (LDLR) suggested the mechanism. Molecular docking revealed that the binding energy between rapeseed peptide and LDLR-PCSK9 molecules was -6.3 kcal/mol and -8.1 kcal/mol. In conclusion, the rapeseed peptide EFLELL exerts a favourable hypolipidaemic effect by modulating the LDLR-PCSK9 signalling pathway.

Anti-Inflammatory and Transepithelial Transport Activities of Rapeseed (Brassica napus) Napin-Derived Dipeptide Thr-Leu in Caco-2 and RAW264.7 Cocultures.

This study aimed to investigate the anti-inflammatory molecular activity of rapeseed napin-derived dipeptide Thr-Leu (TL) using Caco-2/RAW264.7 cell cocultures. This in vitro coculture intestinal inflammation model was used to assess the absorption, evolution, and anti-inflammatory effects of peptides. TL was absorbed by the intestinal epithelial cells with an apparent permeability of (2.48 ± 0.18) × 10-6 cm/s, primarily through the PepT1 pathway. TL treatment exerted anti-inflammatory and restorative effects on the impaired intestinal barrier function by enhancing the expression levels of occludin and ZO-1 in lipopolysaccharide (LPS)-induced Caco-2 cells. No significant change (P < 0.05) was detected in claudin-1 expression levels; however, the occludin expression levels were upregulated through the protein kinase C (PKC) signaling pathway. Compared with the LPS-induced group, TL (2.0 mM) reduced the levels of intracellular inflammation-related enzymes (iNOS: by 50.84%; COX-2: by 49.64%) on the coculture cell model. In addition, the interleukin (IL)-1ß, IL-6, and TNF-α levels in RAW264.7 cells were significantly (P < 0.05) downregulated following TL treatment (2.0 mM) due to the suppression of the phosphorylation of the JNK-independent pathway on the basolateral side of the coculture cell model. These findings highlight the potential use of TL in functional foods or nutraceuticals to prevent intestinal inflammation.

Co-encapsulation of rutinoside and ß-carotene in liposomes modified by rhamnolipid: Antioxidant activity, antibacterial activity, storage stability, and in vitro gastrointestinal digestion.

The surfactant rhamnolipid (RL) was used to modify the liposomes. ß-carotene (ßC) and rutinoside (Rts) were utilized to generate co-encapsulated liposomes through an ethanol injection method that used both hydrophilic and hydrophobic cavities to fabricate a novel cholesterol-free composite delivery system. The RL complex-liposomes loaded with ßC and Rts (RL-ßC-Rts) showed higher loading efficiency and good physicochemical properties (size = 167.48 nm, zeta-potential = -5.71 mV, and polydispersity index = 0.23). Compared with other samples, the RL-ßC-Rts showed better antioxidant activities and antibacterial ability. Moreover, dependable stability was uncovered in RL-ßC-Rts with still 85.2% of ßC storage from nanoliposome after 30 days at 4°C. Furthermore, in simulated gastrointestinal digestion, ßC exhibited good release kinetic properties. The present study demonstrated that liposomes constructed from RLs offer a promising avenue for the design of multicomponent nutrient delivery systems using both hydrophilic.

Rapeseed peptide inhibits HepG2 cell proliferation by regulating the mitochondrial and P53 signaling pathways.

BACKGROUND: Rapeseed peptide, extracted from rapeseed protein, is known to have a variety of biological activities. In this study, the anti-proliferation effect and molecular mechanism of rapeseed peptide on HepG2 cells were investigated. RESULTS: In vitro anticancer experiments showed that the rapeseed peptide NDGNQPL could inhibit HepG2 cell proliferation in a concentration-dependent manner [half maximal inhibitory concentration (IC50 ), 1.56 mmol L-1 ). HepG2 cells were induced by NDGNQPL at a 0.5 mmol L-1 concentration and exhibited a 28.39 ± 0.80% apoptosis rate and a cell cycle arrest in the G0/G1 phase. Meanwhile, rapeseed peptide induced a decrease in mitochondrial membrane potential, an increase in reactive oxygen species (ROS) release, and changes in the nuclear morphology of HepG2 cells, indicating that rapeseed peptide could induce cell apoptosis through the mitochondrial pathway. In addition, rapeseed peptide activated the proliferation-related P53 signaling pathway, in which the expression levels of P53, P21, and cleaved-caspase3 were up-regulated, while the expression levels of murine double minute 2 (MDM2) were down-regulated. In molecular docking simulations, NDGNQPL exhibited a good affinity for the MDM2 molecule, which supported the notion that the rapeseed peptide is able to inhibit MDM2, a negative regulator of P53. CONCLUSION: The current results indicate that the rapeseed-derived NDGNQPL peptide has the potential to inhibit the proliferation of HepG2 cells and promote human health. © 2022 Society of Chemical Industry.

Assessment of Novel Oligopeptides from Rapeseed Napin (Brassica napus) in Protecting HepG2 Cells from Insulin Resistance and Oxidative Stress.

Oligopeptides (Thr-His-Leu-Pro-Lys (THLPK), His-Pro-Leu-Lys (HPLK), Leu-Pro-Lys (LPK), His-Leu-Lys (HLK), and Leu-His-Lys (LHK)) are newly identified from rapeseed napin (Brassica napus) protein-derived hydrolysates with the capability of upregulating glucose transporter-4 (GLUT4) expression and translocation. However, whether each of them enhances GLUT4 expression and translocation and their specific mechanisms remain unclear. Here, we assess the effects of the oligopeptides against insulin resistance (IR) and oxidative stress in hepatocytes and screen out the most antidiabetic one. Specifically, compared with other oligopeptides, LPK not only remarkably elevated glucose consumption to 8.45 mmol/L protein; superoxide dismutase (SOD) activity to 319 U/mg protein; GLUT4 expression and translocation; and phosphorylated level of insulin receptor substrate-1 (IRS-1), phosphatidylinositol 3-kinase (PI3K), and protein kinase B (Akt) (P < 0.05) but also remarkably attenuated the reactive oxygen species (ROS) level to 2255, lactate dehydrogenase (LDH) activity to 20.5 U/mg protein, malondialdehyde (MDA) content to 241 nmol/mg protein, and NO content to 1302 µmol/mL protein (P < 0.05). These findings demonstrated that antidiabetic oligopeptide LPK possessed the most potential to protect HepG2 cells from IR and oxidative stress via activating IRS-1/PI3K/Akt/GLUT4 and regulating common oxidative markers in vitro.

Enhancement of DPP-IV inhibitory activity and the capacity for enabling GLP-1 secretion through RADA16-assisted molecular designed rapeseed peptide nanogels.

The potential of pentapeptide IPQVS (RAP1) and octapeptide ELHQEEPL (RAP2) derived from rapeseed napin as natural dipeptidyl-peptidase IV (DPP-IV) inhibitors is promising. The objective was to develop a nanogel strategy to resist the hydrolysis of digestive and intestinal enzymes to enhance the DPP-IV inhibitory activity of RAP1 and RAP2, and stimulate glucagon-like peptide 1 (GLP-1) secretion of RAP2 by a RADA16-assisted molecular design. The linker of double Gly was used in the connection of RADA16 and the functional oligopeptide region (RAP1 and RAP2). Compared to the original oligopeptides, DPP-IV IC50 of the nanogels RADA16-RAP1 and RADA16-RAP2 decreased by 26.43% and 17.46% in Caco-2 cell monolayers, respectively. The results showed that the two nanogel peptides with no toxicity to cells had higher contents of stable ß-sheet structures (increased by 5.6-fold and 5.2-fold, respectively) than the original oligopeptides, and a self-assembled fibrous morphology. Rheological results suggested that the nanogels RADA16-RAP1 and RADA16-RAP2 exhibit good rheological properties for potential injectable applications; the storage modulus (G') was 10 times higher than the low modulus (G''). Furthermore, the RAP2 and its RADA16-assisted nanogel peptide at the concentration of 250 µM significantly (P < 0.05) increased the release of GLP-1 by 35.46% through the calcium-sensing receptor pathway in the enteroendocrine STC-1 cells. Hence, the innovative and harmless nanogels with the sequence of RADA16-GG-Xn have the potential for use by oral and injection administration for treating or relieving type 2 diabetes.

Screening and identification of high bioavailable oligopeptides from rapeseed napin (Brassica napus) protein-derived hydrolysates via Caco-2/HepG2 co-culture model.

Rapeseed napin (Brassica napus) protein-derived hydrolysates (RNPHs, 1-4) are mixtures of peptides, prior to reaching liver tissue and playing their antidiabetic role, at least being absorbed and metabolized by the intestinal barrier. The study aims at screening and identifying high bioavailable rapessed napin-derived oligopeptides via simulated gastrointestinal digestion and absorption. Specifically, RNPHs were obtained using a novel ultrasound-assisted digestive device. The potential capacity of treating type 2 diabetes mellitus (T2DM) was evaluated preliminarily via enhancing glucose transporter 4 (GLUT4) expression and translocation. Also, absorbable rapeseed napin-derived oligopeptides were screened and identified in a Caco-2/HepG2 co-culture model using liquid chromatography coupled with electrospray ionisation and quadrupole time of flight tandem mass spectrometry (LC-ESI-QTOF-MS). The results involved mainly two aspects. First, absorbable oligopeptides from RNPH-1 (Molecular weight, Mw ≤ 3 kDa) with the highest degree of hydrolysis (DH) were the optimal ones to enhance GLUT4 expression and translocation (P < 0.05). Secondly, oligopeptides (Thr-His-Leu-Pro-Lys (THLPK), His-Leu-Pro-Lys (HLPK), (Ile) Leu-Pro-Lys ((I)LPK), His-Leu-Lys (HLK), and Leu-His-Lys (LHK)), identified from both RNPH-1 and RNPH-2 which significantly enhanced GLUT4 expression and translocation, could be absorbed intact and reached HepG2 cells. These findings indicated that high bioavailable oligopeptides from RNPHs were the potential usefulness to treat T2DM in vitro.

Anti-inflammatory activity of peptides derived from millet bran in vitro and in vivo.

Various food-derived bioactive peptides have been found with potential anti-inflammatory effects. Millet bran peptide is a food-derived bioactive peptide extracted from millet bran, a by-product of millet processing. In this study, the anti-inflammatory effect of millet bran peptides was investigated. A lipopolysaccharide (LPS)-induced RAW264.7 cell and an animal experiment model were established to test the anti-inflammatory activity of millet bran peptides in vitro. As indicated by the results, millet bran peptides could significantly reduce the levels of inflammatory factors, including tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß) and prostaglandin E2 (PGE2), in the LPS-induced RAW264.7 cell. As demonstrated by the animal experiment results, millet bran peptides could mitigate the inflammation of spontaneously hypertensive rats (SHRs). According to the western blotting results, millet bran peptides reduced the phosphorylation level of an extracellular signal-related kinase (ERK), I Kappa B (IKB), p65, and p38 of LPS-induced RAW264.7 cells. As indicated by 16S rDNA sequencing analysis results, millet bran peptides could modify the composition of intestinal microbes. In brief, millet bran peptides could have anti-inflammatory activities in vivo and in vitro and mitigate the inflammation of LPS-induced RAW264.7 cells by regulating the signaling pathways of nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK). The above research has laid a theoretical basis for the application of plant-derived peptides in health food.

Synergistic growth-inhibition effect of quercetin and N-Acetyl-L-cysteine against HepG2 cells relying on the improvement of quercetin stability.

In this study, N-Acetyl-l-cysteine (NAC) as a widely-used antioxidant was first applied to improve the stability of Que in medium. The stability of Que in medium was analyzed, and the growth-inhibition effect of Que and NAC against HepG2 cells was estimated. The results showed NAC could significantly improve the stability of Que in medium (more than 80%), while Que alone in medium was totally degraded within 4 h. Besides, it was found that Que together with NAC could significantly enhance the growth-inhibition effect against HepG2 cells compared with Que alone, with the IC50 value of 40 µM and 200 µM for Que together with NAC and Que alone. Moreover, NAC could inhibit the depletion of GSH induced by Que. The synergistic growth-inhibition effect of Que and NAC against HepG2 cells was attributed to NAC improving Que stability in medium accompanied by NAC inhibiting the depletion of GSH induced by Que. The results showed that NAC could improve the stability of Que and reduce the degradation rate of Que in culture medium. This study can provide a reference for the further study of the mechanism of NAC enhancing the stability of quercetin and the development of broad-spectrum stabilizers.

Removal of anti-nutritional factors of rapeseed protein isolate (RPI) and toxicity assessment of RPI.

We prepared a detoxified rapeseed protein isolate (RPI) by phytase/ethanol treatment based on alkaline extraction and acidic precipitation. Contents of protein, fat, ash, moisture, crude fiber, glucosinolates, phytic acid, and phenolics and color were determined. To evaluate the safety of detoxified RPI, five groups of C57 mice (detoxified RPI [10 and 20 g kg-1]; commercial soybean protein isolate (SPI) [10 g kg-1]; non-detoxified RPI [10 g kg-1]; control) were used in the acute-toxicity test. Bodyweight and pathology parameters were recorded at different time points, followed by macroscopic examination, organ-weight measurement and microstructure examination. After pretreatment of rapeseed meals with phytase (enzyme : substrate ratio, 1 : 5 mg g-1) for 1.5 h and two-time ethanol extraction for precipitated protein, the chemical characteristics in RPI were protein (88.26%), fat (0.57%), ash (2.72%), moisture (1.90%), crude fiber (0.77%), glucosinolates (0 µmol g-1), phytic acid (0.17%), phenolics (0.36%) and whiteness (73.38). Treatment resulted in significant removal of anti-nutritional factors (ANFs) and increased whiteness in detoxified RPI compared with non-detoxified RPI, and lower than in cruciferin-rich canola protein isolate (Puratein®). Experimental-related effects on bodyweight, clinical observations, or clinicopathology, in mice treated with detoxified RPI were not observed except for a decreased thyroid gland/parathyroid gland index in mice treated with non-detoxified RPI. Furthermore, the no-observed-effect level (NOEL) was 10 g kg-1 of detoxified RPI, whereas the no-observed-adverse-effect-level (NOAEL) was the highest fed level of 20 g kg-1 of detoxified RPI. Overall, detoxified RPI prepared by the combined treatment of phytase and ethanol was considered safe under the conditions tested, in which the contents of the main ANFs were reduced significantly.

Antihypertensive activity of the ACE-renin inhibitory peptide derived from Moringa oleifera protein.

Moringa oleifera (MO) leaf is a potential plant protein resource with high nutritional and medicinal value. The study aims to investigate the hypotensive activity and stability of MO leaf peptides. MO leaf protein was extracted and then hydrolyzed with Alcalase to produce the MO leaf protein hydrolysate (MOPH). The MOPH was separated into peptide fractions with different molecular weights by membrane ultrafiltration. The MOPH and ultrafiltration fractions were evaluated for antihypertensive activity. Inhibition of the angiotensin-converting enzyme (84.71 ± 0.07%) and renin (43.72 ± 0.02%) was significantly higher for <1 kDa peptides when compared to other fractions. Oral administration of the <1 kDa component in spontaneously hypertensive rats positively lowers the blood pressure (∼17 mmHg). The <1 kDa component was isolated and purified subsequently; the final active component was identified by mass spectrometry and amino acid sequence analysis. Two highly active ACE (angiotensin-converting enzyme) and renin dual inhibitory peptides Leu-Gly-Phe-Phe (LGF) and Gly-Leu-Phe-Phe (GLFF) were obtained. The two peptides exhibited a good dual inhibitory activity of ACE and renin with IC50 values of LGF (0.29 ± 0.13 mM, 1.88 ± 0.08 mM) and GLFF (0.31 ± 0.04 mM, 2.80 ± 0.08 mM). Furthermore, in vivo models, LGF and GLFF significantly reduced the systolic blood pressure (19.4 mmHg; 18.2 mmHg) and diastolic blood pressure (12 mmHg; 13.8 mmHg) of SHRs (spontaneously hypertensive rats). The peptide transmembrane transport experiments and simulated gastrointestinal digestion experiments with LGF and GLFF showed that they can resist gastrointestinal digestion in a complete form. Thus, bioactive peptides from MO leaf may possess the potential to be used for treating hypertension in humans.

Study of monoglycerides enriched with unsaturated fatty acids at sn-2 position as oleogelators for oleogel preparation.

The effect of using highly unsaturated 2-monoglycerides as oleogelators on the properties of soybean oil oleogels designed to eliminate saturated and trans fatty acids was investigated in this study. We adopted a novel two-step synthesis aiming to increase the yield of the 2-monoglycerides. The optimal synthesis conditions were a substrate weight ratio of 2:1 (w/w), 10% Lipozyme 435 (w/w total reactants), and 4 h of reaction time at room temperature. Under these conditions, the 2-monoglyceride yield (40.69%) increased by 10% compared to that of the conventional synthesis route. Additionally, soybean oil oleogels prepared using 10% 2-monoglycerides with or without rice bran wax were systematically characterized by polarized light microscopy, a texture analyzer, XRD spectroscopy, and rheometry. Comparative studies indicated that a combination of rice bran wax and 2-monoglycerides had synergistic effects on gel properties. A mixture of 4% rice bran wax and 6% 2-monoglycerides was found to provide better oleogels.

Insight into the effect of gluten-starch ratio on the properties of Chinese steamed bread (Mantou).

Chinese steamed bread (CSB) is one of the traditional staple foods of Chinese people, and its quality is mainly affected by wheat gluten and starch. Herein, four different ratios of wheat gluten and starch were selected to investigate its effects on the properties of CSB. It was observed that the surface of CSB gradually became darker, yellower, and shrank with increasing gluten-starch ratio. The hardness and chewiness of CSB decreased with the increasing of gluten-starch ratio, as well as the network structure of CSB was dense and porous. The increase of gluten content could effectively control the migration of water in the CSB. Moreover, with increasing gluten-starch ratio, the crystallinity of starch was reduced from 9.95% to 2.03%. As a result, the ratio of gluten-starch mainly affected the development of gluten network structure and starch gelatinization through the competition of water between gluten and starch in the system, which in turn affected the quality of CSB. Thus, it will provide the basis for the adaptability of wheat flour from different origins as the raw material of CSB processing, and also provide guidance for consumers to select flour with different gluten protein content to prepare steamed bread according to their preferences.

Assessment of the DPP-IV inhibitory activity of a novel octapeptide derived from rapeseed using Caco-2 cell monolayers and molecular docking analysis.

The Octapeptide ELHQEEPL, which was identified from the rapeseed protein napin showed prominent Dipeptidyl peptidase-IV (DPP-IV) inhibitory activity. The objective of this study was to investigate the DPP-IV inhibitory activity and transepithelial transport of ELHQEEPL in an approaching intestinal condition using Caco-2 cell monolayers. ELHQEEPL and its degraded fragments EL, HQEEP, and methylated ELHQEEPL were transported across Caco-2 cell monolayers through different pathways. Compared with the nonbiological enzyme inhibition test, the in vitro experiment on Caco-2 cell monolayers showed that the IC50 value of DPP-IV inhibition increased by 43.11% for ELHQEEPL. There was no significant change in DPP-IV gene expression in the Caco-2 cell monolayers upon treatment with ELHQEEPL. Furthermore, molecular docking predicted that the weaker binding between inhibitory peptide and enzyme for the degradation products from ELHQEEPL during transepithelial transport greatly limited its role in inhibiting DPP-IV. PRACTICAL APPLICATIONS: The DPP-IV inhibitory activity of ELHQEEPL was confirmed using Caco-2 cell monolayers as a novel assessment tool, although its potency was reduced by metabolic degradation. In general, this study reported the use of Caco-2 cell monolayers as a tool for comprehensively studying peptides as sources of DPP-IV inhibitors. A Caco-2 cell-based approach with molecular docking can be adapted for the investigation of intestinal absorption and activity attenuation of food peptides being considered for enzymatic action. Moreover, since the Caco-2 cells express a wide range of enzymes, this method can be used for screening for other active food peptides such as for the inhibitors of ACE and a-glucosidase.

Insoluble-bound polyphenols of adlay seed ameliorate H2O2-induced oxidative stress in HepG2 cells via Nrf2 signalling.

In this study, protective effects of insoluble-bound polyphenol extracts from adlay seed against H2O2-induced oxidative stress in HepG2 cells were investigated. Each fraction of insoluble-bound polyphenol extracts from adlay seed was obtained by separating with Sephadex LH-20 column and semi-preparative HPLC. Ferulic acid was found being the main active component of insoluble-bound polyphenol in adlay seed. The cytoprotective effects of ferulic acid against oxidative challenge were determined by cell viability, intracellular reactive oxygen stress change in HepG2 cells, western blot and apoptosis by flow cytometry. Ferulic acid had a positive correlation with cell viability and a negative correlation with apoptosis. Ferulic acid treatment increased the activity of GSH-PX, CAT, γ-GCS. Moreover, the nuclear factor E2 related factor (Nrf2) protein expression in the ferulic acid group positively correlated with the HO-1, GCLC and NQO1 protein levels. Thus the results demonstrated that ferulic acid, the main active component of insoluble-bound polyphenol in adlay seed could ameliorate H2O2-induced oxidative stress in HepG2 cells via Nrf2 signalling. The research can provide a reference for the in-depth study of its regulatory mechanism and the development of antioxidant related functional food and health products.

Application of ultrasound-assisted physical mixing treatment improves in vitro protein digestibility of rapeseed napin.

The in vitro protein digestibility (IVPD) of napin was studied using different pretreatment methods, including ultrasound, mixing napin with lactalbumin, and ultrasound-assisted protein mixing. The relationships between IVPD, molecular structure, and disulfide bonds were explored, showing that the IVPD of napin was the highest compared with the control when treated with 40% ultrasound power. When the proportion of napin to lactalbumin was 5:5, a synergistic influence between the two proteins was observed. Further investigation showed that the IVPD of napin was clearly improved by treatment with ultrasound-assisted protein mixing. Compared with the single protein in the control, the ß-sheet content in the secondary structure of the mixed protein after sonication was reduced from 45.02% to 37.16%. The ordered protein structure was also disrupted by ultrasound, as supported by fluorescence intensity and surface hydrophobicity analyses. The decreased number of disulfide bonds and conformational changes indicated that the IVPD of rapeseed napin was closely related to the disulfide bond content. This study provides a theoretical basis for improving protein digestibility by combining ultrasound with physical mixing.

Enzyme-catalyzed acylation improves gel properties of rapeseed protein isolate.

BACKGROUND: Although rapeseed protein isolate (RPI) possessed some good functional properties, the use of RPI as an ingredient in the food industry is restricted mainly due to its inferior gelation. The purpose of this study was to improve the heat-induced gel properties of RPI using double processes of acylation and additional transglutaminase catalysis. RESULTS: Scanning electron microscopy showed that the gel formed by native RPI exhibited randomly aggregated particulate network structures whereas transglutaminase (TG)-assisted RPI gels significantly improved gelation properties. More importantly, the combined modifications of RPI using TG-assisted acylation can form a gel with unique percolating and small porous structure. Furthermore, TG-catalyzed 5% acylated RPI gel (100 U g-1 , protein basis) exhibited excellent gel properties in terms of gel strength, thermal stability, surface roughness and apparent viscosity compared to non-treated or single modification of RPI gel as determined by texture analyzer, atomic force microscopy and rheometer. Mechanistically, Fourier-transform infrared spectra and gel dissociation test revealed that TG-catalyzed acylation extensively unfolded the hydrophobic and sulfhydryl residues of RPI, in turn, reinforced re-assembly of protein molecules via hydrophobic interactions and disulfide bonds during gel formation. CONCLUSION: Combined processes of acylation and additional TG catalysis improved the thermal gelation properties by altering inter- and intra-protein structures. Such sequential processes will provide a promising approach to improve the protein gelation that could be potentially applied in the food industry. © 2020 Society of Chemical Industry.

Characterization and analysis of an oil-in-water emulsion stabilized by rapeseed protein isolate under pH and ionic stress.

BACKGROUND: Presently, identifying natural compounds as emulsifiers is a popular topic in the food industry. Rapeseed protein isolate (RPI) is a natural plant protein with excellent emulsifying properties, but it has not been systematically developed and utilized. RESULTS: This study investigated the surface hydrophobicity, wettability, and protein solubility of RPI to further explain its emulsifying behavior in emulsion systems. Nanoemulsions stabilized by RPI at varying protein concentration, pH, and ionic strength were prepared. The size distribution, zeta potential, flocculation index, creaming index, microstructure, rheology, and protein secondary structure of emulsions were measured. The emulsion stabilized by 20 g L-1 RPI at pH 10.0, 200 mmol L-1 ionic strength revealed an appropriate droplet size of 555 nm and the most internal gel strength without creaming phenomenon. Circular dichroism spectroscopy showed a positive correlation between emulsion stability and α-helix ratio, indicating the environment factors affected emulsion stability by acting on its hydrogen bonds. CONCLUSIONS: This study demonstrates that RPI is a practical emulsifier for stabilizing nanoemulsions. About 20 g L-1 RPI can stabilize 100 mL L-1 oil in water; stable emulsions can be formed at most pH conditions (except 7.0); ion addition will aggravate the emulsion flocculation, but also increase the internal gel strength. © 2020 Society of Chemical Industry.