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In this study, an edible film was fabricated by incorporating anthocyanin extract from black rice (AEBR) into acetylated cassava starch (ACS)/carboxymethyl-cellulose (CMC) to enhance the shelf life of pumpkin seeds. The effects of AEBR on the rheological properties of film-forming solutions, as well as the structural characterization and physicochemical properties of the film, were evaluated. Rheological properties of solutions revealed that AEBR was evenly dispersed into polymer matrix and bound by hydrogen bonds, as confirmed by Fourier transform infrared spectroscopy analysis. The appropriate AEBR addition could be compatible with polymer matrix and formed a compact film structure, improving the mechanical properties, barrier properties, and opacity. However, with further addition of AEBR, the tensile strength and water vapor permeability decreased and the tight structure was destroyed. After being stored separately under thermal and UV light accelerated conditions for 20 days, the peroxide value and acid value of roasted pumpkin seeds coated with the AEBR film showed a significant reduction. Moreover, the storage stability of AEBR was improved through the embedding of ACS/CMC biopolymers. These results indicated that AEBR film could effectively delay pumpkin seeds oxidation and prolong their shelf life as an antioxidant material. • An edible film by adding anthocyanin extract from black rice (AEBR) into ACS/CMC was prepared. • The addition of AEBR to ACS/CMC films improved its barrier properties. • The ACS/CMC/AEBR films contributed to extending the pumpkin seeds shelf-life. • AEBR was stable through ACS/CMC biopolymer embedding. [ABSTRACT FROM AUTHOR]

In this study, six types of amino acids (Ala, Phe, Glu, Gly, Ser, and Lys) were combined with glucose to produce Maillard reaction products (MRPs) named G-Ala, G-Phe, G-Glu, G-Gly, G-Ser and G-Lys. The effect of MRPs on bread staling was evaluated through texture and sensory analyses during storage. Furthermore, the study comprehensively analyzed the anti-staling mechanisms of MRPs by examining moisture content, starches, and gluten network changes. The results indicated that G-Gly and G-Glu delayed bread staling, with G-Gly showing the most significant effect. Compared with control, the staling rate and starch crystallinity of G-Gly bread decreased by 24.07% and 7.70%, respectively. Moreover, G-Gly increased the moisture content (3.48%), weakly bound water mobility (0.77%), and α-helix content (1.00%) of bread. Component identification and partial least squares regression further confirmed the aldonic acid, heterocyclic acids and heterocyclic ketones in MRPs inhibit water evaporation, gluten network loosening, and starch degradation, thereby delaying bread staling. [Display omitted] • Glucose-derived Maillard reaction products (MRPs) might enhance bread anti-staling. • Adding MRPs to bread enhanced sensory quality and texture, reducing staling rate. • MRPs restrained the starch retrogradation by retarding the starch crystallinity. • MRPs-enriched bread presented stabler gluten networks and higher α-helices content. • Heterocyclic ketones, aldonic and heterocyclic acids of MRPs inhibited bread staling. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes a detailed investigation of ultrafiltration of polysaccharides from rapeseed. Four different commercial membranes made of polyvinylidene fluoride kynoar (PVDF) and polyether sulfone were used. During the preliminary treatment, rapeseed was in turn crushed, dehulled, defatted, homogenized and deproteinized. And then the resulting solution was subjected to ultrafiltration (UF) using three different molecular weight cut-off membranes (3, 8 and 12kDa). The factors, namely, transmembrane pressure and solution conditions (pH, ionic content and temperature), that affected permeate fluxes were optimized. The results showed that transmembrane pressures, feed pH and temperature influenced permeate fluxes greatly, but ionic content hardly had any positive effect. Furthermore, the effects of ultrafiltration were evaluated in terms of recovery and purity of resulting polysaccharides. The results showed that the membrane of 3kDa MWCO ensured not only the highest recovery of polysaccharides, but also high purity, compared to the two others. Finally, the rejected polysaccharides were also characterized in terms of molecular weight distribution (MWD) by size exclusion chromatography in HPLC. The findings thus clearly suggest purification of polysaccharides from rapeseed by the membrane of 3kDa MWCO is feasible with high recovery and purity. [Copyright &y& Elsevier]

Effects of red raspberry extract (RRE) intake on hyperlipidemia mice induced by high-fat diet (HFD) were investigated in this study. After intragastric gavage of RRE for 8 weeks, the body weight and the adipose tissue mass of mice in RRE administration groups significantly (p < 0.05) decreased compared to the group without RRE treatment. RRE treatment significantly (p < 0.05) lowered triglyceride and total cholesterol levels of hyperlipidemia mice. Pparα, Hmgcr, Ldlr, Cyp7a1, Acsl3, Pnpla2 and Pin4 were confirmed as the regulatory genes by transcriptome analysis and qRCR validation. According to KEGG pathway analysis, target genes such as Cyp7a1 and Pin4 were further regulated by the activation of PPARα resulting from RRE supplementation. Meanwhile, liver cholesterol synthesis and conversion were inhibited by the expressions of Hmgcr and Cyp7a1 genes regulated by RRE intake, and Ldlr gene was down-regulated to limit the transport of cholesterol. In addition, RRE treatment could accelerate the conversion from triglyceride to fatty acid. To conclusion, RRE intake would be a protection against diet-induced hypertriglyceridemia. Image 1 • RRE supplementation attenuated hyperlipidemia and oxidative stress in the HFD mice. • RRE intake regulated PPARa expression to further ameliorate lipid metabolism disorder. • RRE intake reduced Hmgcr expression resulting in lower cholesterol. • RRE treatment could accelerate the conversion from triglyceride to fatty acid. [ABSTRACT FROM AUTHOR]

The incidence of food allergy has been increasing in recent years, but the prevention, diagnosis, and treatment of food allergy remain challenges in the world. Food allergen epitope mapping technology can help us identify the epitope sequence and structure, which is conducive to the development of food allergy prevention, diagnosis, and treatment methods. Moreover, the information about allergic epitopes also plays a positive role in the development of new hypoallergenic or non-allergenic food products in the industry. This article systematically reviews state-of-art research progress and development trend of food epitope mapping technology based on the advantages and disadvantages as well as the potentials of each method. The future development direction and trend of food protein allergen epitope mapping technology were also discussed, with a view to providing a reference for the identification and characterization of food allergens. Compared with traditional technologies including peptide scanning technique, novel technologies have the advantages of high specificity, high sensitivity, high accuracy, and high-throughput. Although some progress has been made in the identification and characterization of food protein allergen epitopes, a large number of epitopes have not yet been identified so far. Some work is still needed for invention of new epitope mapping technology, establishment of systematic and comprehensive databases, and development of allergic omics in the future. • Specificity between IgE antibodies and epitopes is indicator of food allergy. • Recent advances in techniques have enabled efficient prediction of epitopes. • Current and development of food epitope mapping technologies were discussed. • Epitope identification mechanism would be better understood. • Diagnosis/prognosis of food protein allergies would be more effectively. [ABSTRACT FROM AUTHOR]

Dried water dropwort (Oenanthe javanica DC.) was treated by coarse and superfine grindings, respectively. Four particle sizes water dropwort powders (WDPs) of 250-150, 150-75, 75-38 and < 38 μm were sieved, then the corresponding particle size, color, chemical components, thermal, functional, dissolution and dispersion properties were investigated. Results showed that the surface area, greenness, brightness, and soluble dietary fiber contents of WDPs increased after superfine grinding. With the decreasing of particle sizes, the solubility, water holding and swelling capacities, as well as thermal stability increased significantly, while the oil holding capacity decreased. Fourier-transform infrared spectroscopy (FTIR) analysis indicated that the main chemical structures were not destroyed after superfine grinding. The dissolution of flavonoids, total polyphenols, soluble proteins and polysaccharides were improved gradually as particle sizes decreased. The ultrafine WDPs (<38 μm) exerted highest dispersibility in colloidal solutions, especially in the solution of xanthan gum, which could be valuable in the beverage developments. Unlabelled Image • Water dropwort powders (WDPs) of 250–150, 150–75, 75–38 and <38 μm were prepared. • Soluble dietary fibers increased with improving of color in WDPs. • Hydration properties were enhanced with reduction of oil binding capacity in WDPs. • Dissolution of phytochemical components increased as reduction of particle size. • WDPs of <38 μm exerted better dispersibility and stability in colloidal solutions. [ABSTRACT FROM AUTHOR]

Abstract Effects of Maillard reaction products derived from 1 to 3 kDa soybean peptides (MRPF3) on aging ICR mice were investigated. Seven animal groups were established for 5 weeks, including one normal group and six D-galactose (1000 mg kg−1/day) treated groups. Aging control was D-galactose + saline solution, and positive controls were D-galactose + ascorbic acid (Vc) (400 mg kg−1/day) and oligofructose (400 mg kg−1/day), respectively, while the test groups are D-galactose + high (800 mg kg−1/day), medium (400 mg kg−1/day) and low (200 mg kg−1/day) doses of MRPF3. Compared with the aging controls, food intake, body weights and organ indexes returned to normal after feeding with MRPF3, and the color of feces as well as the fluorescence intensity of urine increased. The content of malondialdehyde (MDA) in the liver significantly decreased with the intake of MRPF3, and the activities of SOD and GSH-Px and the total antioxidant capacity of serum significantly increased. The abundance ratio of Bacteroidetes and Firmicutes significantly decreased in MRPF3 groups, and the abundance of Lactobacillus significantly increased, while potentially pathogenic bacteria such as Porphyromonadaceae significantly decreased. Our results showed that MRPF3 might offer a potent retardation potential for aging. Graphical abstract Image 1 Highlights • Maillard reaction products derived from 1 to 3 kDa soybean peptides (MRPF3) were made. • Aging ICR mice were treated with MRPF3 at high, medium and low doses, respectively. • Physiological indexes of aging mice returned to normality after feeding with MRPF3. • Malondialdehyde content in liver decreased, antioxidant capacity of serum increased. • Pathogenic bacterial were inhibited while beneficial ones proliferated. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Rapeseed peptide and d -xylose were used to develop Maillard reaction products. • Reaction with or without cysteine and various temperatures were considered. • High temperature promoted the formation of browning products and volatiles. • Cysteine addition was favor to generation of sulfur-containing compounds. • Furans and nitrogen oxides could be produced without cysteine. Abstract Rapeseed peptide was used to produce flavor enhancer via heating with d -xylose at various temperatures (80–140 °C) at reaction pH 7.4 for 2 h with or without l -cysteine (RXC or RX). Effects of temperatures and l -cysteine on the Maillard reaction products (MRPs) were investigated by the determinations of pH, color, free amino acids (FAA), and volatile compounds, as well as E-nose and E-tongue analyses. Partial least square regression (PLSR) method was further applied to explore the correlations. Results suggested that pH decreased more significantly in RXCs, and a more dark brown color was observed in RXs with the increase of heating temperatures. The lowest bitterness MRPs were obtained by heating at 140 °C with cysteine (RXC-140), while the highest umami and saltiness sample was found in RX-100. Bitter and umami FAAs were present in greater amounts at higher temperatures with cysteine. Furthermore, RXC showed a meat-like flavor due to the generation of sulfur-containing compounds, and more furans and nitrogen-containing compounds were detected in RX, along with a caramel-like flavor. [ABSTRACT FROM AUTHOR]

• pH-shifting was effective in reducing lectin allergy combining with autoclaving. • More hydrophobic exposures were confirmed in refolding process of pH-shifting. • β-turn increased and random coil decreased after the combining treatment. • Lectin aggregation was observed after autoclaving and enhanced with low pH treated. • Flexible structure and exposure of enzyme cutting sites improved digestibility. Combined effects of pH-shifting and an autoclaving cycle (121 °C, 15 min) on red kidney bean lectin (RKBL) were investigated using intrinsic and extrinsic fluorescence, UV, FTIR, DSC, SEC, dot-blot analysis and in vitro digestibility. Spectroscopic studies suggested that the protein refolding was stable after 3 h incubation with the hydrophobic exposure after pH-shifting, and hydrophobicity was significantly increased with the formation of more looser structure, which would influence the structural stability of known epitopes. In details, the increase of β-turn and reduction of random coil was related with the lower denaturation enthalpy, while the protein aggregation was also observed in acidic treated samples after autoclaving. Lower antigenicity and good digestibility suggested the exposure of enzyme cutting sites, and confirmed the effectivity of pH-shifting prior to the autoclaving. Then the results would be beneficial to the development of hypoallergenic kidney bean foods. [ABSTRACT FROM AUTHOR]

Highlights • Lectin of black turtle bean were incubated in acidic buffers for various times. • A steady state of lectin tertiary structure was formed by low pH treatment for 8 h. • Low pH treatment could cause structure alterations significantly and dissociation. • Allergenicity and digestibility of lectin were reduced by low-pH induced process. Abstract Lectin was incubated in corresponding acidic buffers (pH 1.0–3.5) for a certain period (0.5, 1, 2, 4, 8, 12 and 24 h) at 25 °C. Low-pH induced changes in structure, allergenicity and in vitro digestibility of lectin from black turtle bean (Phaseolus vulgaris L.) were investigated in the present study. Results indicated that the alteration in structure was a progressive unfolding process mainly depending on pH environment, and the treated lectin attained a stable state at 8 h. Electrophoretic, dynamic light scattering (DLS) and size exclusion chromatography (SEC) analyses suggested that lectin monomers appeared in the solutions of pH < 2.0. Differential scanning calorimetry (DSC) confirmed that thermal stability of lectin weakened in low pH environments. Furthermore, ELISA and in vitro digestion assay showed allergenicity and digestibility significantly decreased with the structural alterations. These results showed low-pH treatments have great potential to reduce the damage of legumes protein consumption. [ABSTRACT FROM AUTHOR]

Abstract Maillard reaction products (MRPs) were obtained by using the xylose and soybean peptide system through a 2 h heating at pH of 7.6. Cysteine addition and thermal treatment at 80, 100, 120 and 140 °C were investigated via E-nose and E-tongue, free amino acids (FAA) and GC–MS analyses of MRPs. Afterwards, the combined effects were performed using the partial least square regression (PLSR). Results suggested that MRPs without cysteine addition (XSs) had stronger browning intensity, and the cysteine would be beneficial to the pH reduction with heating temperature increasing. PLSR analysis revealed that MRPs with cysteine addition heated at 140 °C (XSC-140) showed the lowest bitterness, and XS-100 had the highest umami and saltiness. Both bitter and umami FAA increased with the addition of cysteine, and more furans and nitrogen-containing compounds formed in the XSs brought caramel-like flavor, while XSCs exhibited meat-like flavor attributed to sulphides generation. Highlights • Maillard reaction products with or without cys were got at various temperatures. • High temperature promoted the formation of browning products and volatiles. • Cysteine addition reduced the formation of color, bitterness, umami and saltiness. • Higher umami and saltiness could be obtained at 100 °C heating without cysteine. • Lower bitter but meaty flavor could be obtained at 140 °C heating with cysteine. [ABSTRACT FROM AUTHOR]

• Pre-germination was used to improve the nutritional value of brown glutinous rice. • Antagonism between ultrasound treatment and CaCl 2 stress was explored in soaking. • Both CaCl 2 and ultrasonic treatments improved GABA production during germination. • Energy metabolism, lipid metabolism and protein hydrolysis were enhanced. • Low-frequency ultrasound with salt stress would short the germinated time. In order to fortify γ-aminobutyric acid (GABA) of brown glutinous rice (BGR), pre-germination strategy was employed, and effects of low-frequency (28 kHz) ultrasound treatment combined with CaCl 2 stress on the sprout length, germination rate, morphology, color, water, total polyphenol content (TPC), starch, protein, GABA contents and relevant metabolites were investigated. The germination rate would be inhibited under CaCl 2 concentration ≥ 2.0 % during 24 h soaking without ultrasound treatment, and no significant difference was also observed combined with 9 h ultrasound treatment. Ultrasound treatment was beneficial to water absorption, TPC enrichment, energy metabolism, lipid metabolism and protein hydrolysis. Higher contents of GABA (3.29 folds), pyruvic acid (7.63 folds), glycerol (4.88 folds), glutamate (2.02 folds) and glucose (1.32 folds) were obtained due to the antagonistic effect between the 30 w ultrasound treatment and 2.0 % CaCl 2 stress at the 9 h pre-germination, and energy, lipid and protein metabolomic pathways were all involved in the GABA accumulation. [ABSTRACT FROM AUTHOR]

In this work, we investigated PEGylated black kidney bean protein isolates (BKBPI) by PEG succinimidyl carbonate (PEG-SC), PEG succinimidyl succinate (PEG-SS) and PEG succinimidyl propionate (PEG-SPA) conjugation. The functional properties, thermodynamic stability, in vitro digestion stability, and hemagglutination activity of the modified products were evaluated. The degree of PEGylation was measured, and FTIR analysis revealed that protein-PEG conjugations were formed, and that no obvious changes in water- and fat-holding capacities were observed. The solubility, emulsifying property, and foaming property were all improved through the modification, while, higher thermodynamic stability was achieved with the increase in Td values and reduction of ΔH. The PEGylated proteins were found to be more resistant to in vitro digestion, and the hemagglutination activity was significantly ( P <  0.05) decreased, indicating the higher safety of the protein isolate. The results showed that the functional properties, thermodynamic stability, and biological safety of BKBPI were improved by PEGylation, which could serve to increase the applications for this protein. [ABSTRACT FROM AUTHOR]

Four peptide fractions PF1 (>5 ;kDa), PF2 (3–5 ;kDa), PF3 (1–3 ;kDa), PF4 (<1 ;kDa) were isolated from soybean hydrolysate using the ultrafiltration method. Then, d -xylose and l -cysteine were reacted with specific peptide solution at 120 ;°C for 2 ;h, and the molecular weight distribution (MWD), pH, colour, browning intensity, DPPH radical-scavenging activity, free amino acids and sensory characteristics of corresponding Maillard reaction products (MRPF1, MRPF2, MRPF3 and MRPF4) were evaluated, respectively. Peptides with low molecular weight showed higher contribution to the changes of pH, colour and browning intensity during Maillard reaction. The DPPH radical-scavenging activity of PF4 was significantly improved after Maillard reaction. Aroma volatiles and PLSR analysis suggested MRPF3 had the best sensory characteristics with higher contents of umami amino acids and lower of bitter amino acids, therefore it could be deduced that the umami and meaty characteristics were correlated with the peptides of 1–3 ;kDa. [ABSTRACT FROM AUTHOR]

Hard white winter wheat ( Triticum aestivm L.) bran was grinded by an eccentric vibratory mill below 30 ± 0.5 °C, and the effect of processing times (15, 20, 25 and 30 min) on the physicochemical and antioxidant properties of the superfine powder was investigated with disc-milled powder as control in the study. After vibratory milling treatment, the particle size of powder effectively reduced to a micron scale and the brightness increased, as well as the contents of soluble dietary fiber and phytic acid increased. Compared with the control, the eccentric vibratory milled bran powder showed higher values in bulk density (from 0.27 to 0.39 g/mL), tapped density (from 0.31 to 0.76 g/mL), water holding capacity (from 4.20 to 7.00 g/g), swelling capacity (from 1.67 to 2.87 g/g) and oil binding capacity (from 1.50 to 2.61 g/g), while lower values in angles of repose and slide in the processing time sequence. Meanwhile, the thermal stability was enhanced. And the decreases of IC 50 values for DPPH radical scavenging activity and ferrous ion-chelating activity suggested the improvement of antioxidant activity for bran superfine powder. The results indicated that the eccentric vibratory milled wheat bran superfine powder have various potential applications as food and pharmaceutical additives to improve the uniformity and/or to enhance functionalities of final products. [ABSTRACT FROM AUTHOR]

The water-soluble polysaccharides from bamboo shoots ( Phyllostachys praecox ) (WBP) were isolated, and the characterizations as well as prebiotic activities were investigated. The yield of WBP was 7.58 ± 0.31% under optimal hot-water extraction conditions. Two fractions, i.e., WBP-1 and WBP-2 with molecular weight of 83.50 kDa and 80.08 kDa, respectively, were purified by chromatography. Both the polysaccharides fractions were identified as heteropolysaccharides-protein complexes composed of 15 kinds of common amino acids in protein part and rhamnose, arabinose, xylose, mannose, glucose and galactose in different molar ratios in polysaccharide part. The existence of α- and β-glycosidic linkages between the sugar units was confirmed by FTIR and NMR spectra. Compared with the blank control and the reference of FOS, WBP-1 and WBP-2 significantly increased the numbers of Bifidobacterium adolescentis and Bifidobacterium bifidum ( P < 0.05), which contributed to the production of organic acids, suggesting that the polysaccharides have potential prebiotic properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • Raw oils and enzymatic hydrolysis-thermal oxidation (ENTH) oils were prepared. • Corn, peanut, and olive oil after ENTH could better promote Maillard reaction (MR). • Coconut oil and palm oil had higher oxidation stability during MR processing. • Oleic acid and linoleic acid oxidation could promote the formation of aldehydes. • ENTH oils could reduce O, N, and S-containing heterocycles content in MR system. Vegetable oils with different unsaturated degrees (corn > peanut > olive > palm > coconut) and corresponding enzymatic hydrolysis-thermal oxidation (ENTH) oils were added into D-xylose and L-cysteine Maillard reaction (MR) system, respectively, for potential meaty aroma production. Results indicated that coconut oil and palm oil had lower peroxide, p -anisidine, total antioxidant values, and malondialdehyde content after ENTH and MR. Corn, peanut, and olive oils after ENTH could significantly promote MR because they caused the lower pH, higher reactants depletion, and higher browning degree in the water phase separated from the oil-Maillard reaction system. Additionally, the volatiles were mainly formed from oil phase. Corn, peanut, and olive oils were beneficial to volatiles formation in the oil-MR system due to fatty acid oxidation, especially oleic acid and linoleic acid. Meanwhile, compared to raw oils, adding ENTH oils to the MR system could reduce the content of oxygen, nitrogen, and sulfur-containing heterocycles. [ABSTRACT FROM AUTHOR]

In vitro digestibility, prebiotic activity and chemical composition of polysaccharides from rapeseed were deliberately studied in this paper. After preliminary treatments, two fractions of polysaccharides (RP1 and RP2) were obtained after purification by DEAE-cellulose and Sephadex G-100. Their primary structural feature and molecule weights were characterized. Furthermore, their digestibility was also evaluated by artificial gastric juice and α-amylase. Finally, their proliferative effect on bifidobacteria and lactobacilli and acid production of the resulting probiotics in vitro were investigated. The results showed that RP1 and RP2 were homogeneously protein-bound polysaccharides with molecular weights of 28.51 and 6.55 kDa, respectively. They were resistant to hydrolysis by artificial gastric juice and α-amylase. Moreover, they could also significantly stimulate the tested probiotics to proliferate and produce organic acids. These findings clearly suggest the polysaccharides from rapeseed are potential to be exploited as novel prebiotics. [ABSTRACT FROM AUTHOR]

• Two-step protocol with 70–80% (v/v) ethanol recover more prolamins from kidney beans. • MS data showed the composition diversity of prolamins from various kidney beans. • Seven prolamins were clustered into three main groups related to seed coat colors. • LSKB, BSKB, and RKB extractions have higher hydrophobicity and better OAC. • Hydrophobicity was related to the compositions and structures of prolamins. Ethanol protocol, two-step protocol and enzymatic extraction were used to extract prolamins from seven kidney beans (P. vulgaris L.) compared with Osborne protocol. 70–80% (v/v) ethanol concentrations were beneficial to the extraction, and two-step protocol was conducive to higher prolamin content. Varied protein subunits were observed in electrophoresis profiles, and further differences in composition were identified by LC-MS/MS while potential functions were annotated. Stronger hydrophobicity was found with prolamins enrichment from light speckled kidney bean (LSKB), black speckled kidney bean (BSKB), and red kidney bean (RKB), which was negative correlation with α-helix content based on the principal component analysis (PCA). The crude prolamins from the two kinds of white kidney beans possessed higher sulfhydryl and exhibited better water holding capacity (WHC), while higher oil absorption capacity (OAC) was observed in LSKB, BSKB, and RKB. Compared with zein, kidney bean prolamins could be used as food packaging materials due to hydrophobicity. [ABSTRACT FROM AUTHOR]

• Low pH-shifting was used in black turtle bean protein isolate treatment. • Protein isolates were adjusted to neutral from pH 3.0, 2.0, 1.5, 1.0 incubations. • Protein was unfolded with exposure of buried hydrophobic residues after treatment. • Hydrophobic functionalities were improved, with decrease of hydrophilic properties. • Lower hemagglutination and immunoreactivity were obtained with better digestibility. Low pH-shifting was firstly applied in the black turtle bean (Phaseolus vulgaris L.) protein isolate treatment by acidic (pH 1.0–3.0) buffer incubation for 8 h, then was adjusted to pH 7.2 and kept 3 h for protein stabilizing. Mild loss of secondary structure was confirmed in the protein isolate after low pH-shifting treatment by CD and FT-IR analyses. Intrinsic fluorescence, UV spectra, surface hydrophobicity, SH content and SDS-PAGE analyses indicated the protein conformation was unfolded with the exposure of much more buried hydrophobic residues, which would result in the enhancement of emulsifying properties, foaming properties and fat holding capacity, and lead to the reduction of solubility and water holding capacity. Furthermore, lower immunoreactivity was observed by the ELISA, and improved digestibility was found in in vitro digestion assay. Our results suggested the low pH-shifting treatments would broaden the application of bean protein isolate with better hydrophobic processing functions and safety. [ABSTRACT FROM AUTHOR]

• Effects of pH and heating on BKBL IgE-binding capacity were characterized by RSM. • IgE-binding capacity reduction was related with the structural change of BKBL. • Low-pH incubated BKBL was a bit resistant to structural alterations during heating. • Combination of pH and heating was effective to reduce IgE-binding capacity of BKBL. Combined effects of pH and thermal treatments on black kidney bean lectin (BKBL) were investigated by response surface methodology (RSM). Low-pH (1.0, 2.0, 3.0) incubation decreased hemagglutination activity (HA) and IgE-binding capacity, but the activities would be restored when the lectin was treated by pH shifting to 7.2. Conformational structure analyses indicated that low-pH induced protein unfolding and pH-shifting treatment resulted in a limited structural rearrangement. Mild heating, such as 60 °C for 3 min, slightly increased the HA and IgE-binding activities of pH shifted BKBL, but no obvious effects in the pH 1.0 incubated BKBL. High-temperature and long-time treatment might induce the protein aggregation, further decreased HA and IgE-binding capacities. RSM results showed both IgE-binding capacity and HA were the lowest under the combination of pH 1.0 incubation with 80 °C heating for 15 min or pH shifting from 1.0 to 7.2 with 100 °C heating for 10 min. [ABSTRACT FROM AUTHOR]

• Protein extracted at pH 9.0 had lower glucosinolates, phytic acid and sinapine. • Protein extracted at pH 9.0 had lighter colour and lower D-amino acid content. • Protein obtained at pH 4.5 had the lowest glucosinolates, phytic acid and sinapine. • Water/oil absorption, foaming and emulsifying features decreased as pH decreased. • The α-polypeptide of cruciferin and napin showed gastric digestive resistance. Cold-pressed rapeseed meal with high protein content (38.76% protein dry weight basis) was used to prepare rapeseed protein isolates (RPIs) by alkaline extraction (pH 8.0, 9.0, 10.0, 11.0, 12.0 and 13.0) and acid precipitation (pH 3.0, 3.5, 4.0, 4.5, 5.0 and 5.5). The protein with an intact structure and the highest yield (65.08%) was obtained at extraction pH 9.0 and precipitation pH 4.5, accompanied by the lowest D-amino acid content, the lightest colour and the lowest contents of glucosinolates (2.85 mmol/kg), phytic acid (1.05 mg/g) and sinapine (0.68 mg/g). Additionally, water/oil absorption, foaming and emulsifying capacities decreased with decreasing precipitation pH, while the solubility showed the reverse trend. During gastric simulation digestion, the α-polypeptide of cruciferin and napin in the RPIs showed digestive resistance. Overall, pH regulation might be an effective method to isolate high quality RPIs for use in the food processing industry. [ABSTRACT FROM AUTHOR]

• SPI was modified by low pH shifting with hydrophobicity enhancement. • SPI-SPSS conjugates were easily obtained by Maillard reaction. • Submicro particles were formed by heating self-assembly reaction. • Improvement of hydrophobicity of SPI could promote submicron gelling properties. In the present study, the soybean protein isolate (SPI) was treated by pH shifting process, as the protein was incubated in low pH solutions (pH 1.5–3.5) for 12 h, following neutralized to pH 7.0 and held for 4 h, which resulted in a conformation unfolding/refolding confirmed by the fluorescence spectra and a substantial increase in α-helix content revealed by circular dichroism (CD) spectra, along with the increased exposure of hydrophobic and sulfhydryl groups. In addition, the heat-induced gelation process and enhanced gel strength of pH 3.0 and 3.5 shifted SPIs were observed. Maillard reaction was then applied and the glycosylated SPI was further applied to the sub-micron gel particles formation. Results showed that low-pH shifting obviously improve the glycosylation ability of SPI as the conjugation degree and browning degree were enhanced. The sub-micron gel particles with core–shell structure and the average sizes of 100–250 nm were formed via heating self-assembly reaction and confirmed through Z-average of particle size, meanwhile, the increasing stability of gel particles in the solution was determined by Zeta potential analysis, suggesting that the improvement of hydrophobicity and glycosylated ability of SPI could promote gelling properties. Hence, the protein modification stage of pH shifting process would provide a great potential application in the formation of nano- or microscale gel particles. [ABSTRACT FROM AUTHOR]

As a well-known allergenic indicator in kidney beans, lectins have always been the serious threats for human health. Herein, we introduced a new label-free voltammetric immunosensor for the direct determination of kidney bean lectin (KBL) with potential allergenic activity. Gold nanoparticles-polyethyleneimine-multiwalled carbon nanotubes nanocomposite was one-pot synthesized and modified onto the glass carbon electrode to enhance catalytic currents of oxygen reduction reaction. The KBL polyclonal antibody, acquired from rabbit immunization, was orientedly immobilized on the electrode modified with recombinant staphylococcal protein A via fragment crystallizable (Fc) region of antibody. Under the optimized condition, the immunosensor displayed a good linear response (R2 = 0.978) to KBL with a range from 0.05 to 100 μg/mL and a detection limit of 0.023 μg/mL. Simultaneously, the immunosensor exhibited well selectivity, interference-resistant ability, stability (4 °C) and reproducibility. Compared with the conventional enzyme-linked immunosorbent assay (ELISA) method, the immunosensor was successfully applied to quantify allergenic activity of lectin in raw and cooked (boiled for 30 min) kidney bean milk samples. This new approach provides new perspectives both for rapid quantification of lectin in kidney beans-derived foodstuffs and as a real-time monitoring tool for the allergenic potential during the whole production and consumption process. • First electrochemical immunosensor report for allergenic activity of lectin. • Oriented antibody immobilization using recombinant staphylococcal protein A. • AuNPs-PEI-MWCNTs nanocomposite was used for signal amplification. • The immunosensor shows high sensitivity and fast response to kidney bean lectin. • Allergenicity-recognizable detection of immunosensor towards kidney bean milks. [ABSTRACT FROM AUTHOR]