Effect of alkaline treatment duration on rapeseed protein during pH-shift process: Unveiling physicochemical properties and enhanced emulsifying performance.

This study aims to investigate the influence of alkaline treatment duration (0-5 h) on the physicochemical properties and emulsifying performance of rapeseed protein during pH-shift process. Results showed that a 4-h alkaline treatment significantly reduced the particle size of rapeseed protein and led to a notable decrease in disulfide bond content, as well as alterations in subunit composition. Moreover, solubility of rapeseed protein increased from 18.10 ± 0.13% to 40.44 ± 1.74% post-treatment, accompanied by a âˆ¼ 40% enhancement in emulsifying properties. Morphological analysis revealed superior plasticity and sharper contours in 4-h alkali-treated rapeseed protein emulsions compared to untreated counterparts. Rheological analysis indicated higher viscosity and elasticity in the alkali-treated group. Overall, 4-h alkaline treatment markedly enhanced the multifaceted functional attributes of rapeseed protein during pH-shift process, rendering it a promising emulsifier in the food industry.

Investigating the physicochemical properties and air-water interface adsorption behavior of transglutaminase-crosslinking rapeseed protein isolate.

Improving the technical functionality to adapt to the application of complex food systems is an important challenge for the development of plant protein ingredients. Herein, the correlation between the physicochemical properties and interfacial adsorption behavior of rapeseed protein isolate (RPI) at the air-water interface after transglutaminase (TG) treatment was investigated. The results of cross-linking degree, Fourier transform infrared spectroscopy (FTIR) and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that the TG enzyme was able to catalyse cross-linking between lysine and glutamine residues of RPI. The foaming capacity of RPI was enhanced from 120 % to 150 % after TG cross-linking 5 h, whereas the average size (210-219 nm) of the RPI determined by dynamic light scattering did not change significantly. Besides, the hydrophobicity tended to increase overall under the enzyme treatment, while the surface electrostatic potential decreased. The former indicates the unfolding of the protein and reduces the kinetic barriers to protein adsorption at the air-water interface, with a consequent increase in disulfide bonding and surface pressure. Furthermore, as the enzyme treatment time increased, a significant increase in protein content of foam by 33.86 %. These findings provide novel insight into the foaming mechanism of TG cross-linking RPI.

Effect of Lactobacillus plantarum fermentation on the physicochemical properties and flavor of rice protein-carboxymethylcellulose complexes.

BACKGROUND: Fermentation is known to enhance the nutritional profile and confer unique flavors to products. However, the resultant effects on stability and physicochemical properties remain unexplored. RESULTS: This study aims to elucidate the influence of fermentation on the stability and organoleptic characteristics of a rice protein beverage stabilized by carboxymethyl cellulose (CMC). The findings revealed that the average aggregate size escalated from 507 to 870 nm, concurrently exhibiting a significant increase in surface potential. The aggregation enhancement was substantiated by evident morphological changes and confocal laser scanning microscopical (CLSM) observations. A negative correlation was discerned between the physical stability of the beverage and fermentation duration. Moreover, flavor analysis of the beverage post a 3 h fermentation period highlighted an increase in aromatic ester compounds, thereby intensifying the aroma. CONCLUSION: The study corroborates that fermentation can detrimentally influence product stability while concurrently improving its flavor profile. By establishing a mix ratio of 10:1 for rice protein and CMC and forming a relatively stable system through electrostatic interaction at a pH of 5.4, a flavorful rice protein beverage can be derived post 3 h-fermentation process. These findings offer insights into the impact of varying fermentation durations on the stability and flavor of polysaccharide-based rice protein beverages. © 2023 Society of Chemical Industry.

Solubility and conformational characterization of rice glutelin after high temperature treatment.

Enhancing the solubility of rice glutelin in neutral aqueous solution is the prerequisite for the development of rice protein drinks and ingredients. Herein, glutelin was first dissolved in an aqueous solution of pH 12, and then heated at 121 °C for 20 min. The results showed that the solubility of glutelin increased from 2.55 mg/mL to 20.7 mg/mL at pH 7. The size of glutelin aggregates at pH 7 decreased from 900 nm to 400 nm after high temperature treatment (HTT), which was confirmed by atomic force microscopy. The results of small angle X-ray scattering showed that HTT induced the conformational unfolding of glutelin, and the protein in the aggregate was rod like shape as well as the mean square rotation radius decreased from 64.9 to 54.8 Å. Furthermore, Raman spectrum results also agree with the unfolding of glutelin conformation, which was mainly reflected in the changes of tyrosine and tryptophan residues, as well as the decreasing of α-helix content and increasing of ß-sheet content. After being freeze-dried, HTT glutelin has a re-solubilization capacity of 15.48 mg/mL in pH 7 aqueous solution, which was superior to that of spray dried glutelin powder (pH 7, 9.19 mg/mL).

Antioxidant mechanism of a newly found phenolic compound from adlay (NDPS) in HepG2 cells via Nrf2 signalling.

An in-depth understanding of the bioactive mechanism of phytochemicals has a good guiding value for the design of related functional foods. Herein, the effect of N1, N5- di-[(E)-p-coumaroyl]-spermidine (NDPS) originated from adlay on protecting HepG2 cells from oxidative stress was evaluated by MTT assay, western blot and qRT-PCR. After pre-treatment of NDPS, the activities of antioxidant enzymes (including superoxide dismutase, glutathione peroxidase, γ-glutamyl cysteine synthetase and heme oxygenase-1) were increased, as well as the level of proteins and gene expressions were elevated. Moreover, the γ-GCS, HO-1, SOD and GPx protein level were enhanced for the cells with NDPS treatment compared to both positive control and negative control groups. These findings suggested that NDPS could protect HepG2 cells from oxidative stress by increasing the antioxidant enzymes regulated by Nrf2/ARE pathway.

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.

Relationship between gel properties and water holding of ovalbumin-carboxymethylcellulose electrostatic complex hydrogels.

The relationship between the water holding (WH) and gel properties of protein-based hydrogels is important for designing and regulating the texture and sensory properties of foods. Herein, the relation among WH and heat-set gel properties of ovalbumin (OVA)-carboxymethylcellulose (CMC) electrostatic complexes was explored. The results showed that the gels exhibited homogeneous and dense structure and good WH compared with pure OVA at pH 4.6, while Young's modulus decreased significantly (P < 0.05). This was closely related to the inhibition of the electrostatic interaction on the formation of large protein aggregates during heat treatment (90 °C, 30 min). Specially, the CMC1.2 (the degree of substitution was 1.2) with higher charge density showed stronger interference than CMC0.7 (the degree of substitution was 0.7) for the gel network structure and properties. Moreover, the addition of salt ions could enhance the gel strength. Meanwhile, the coarseness and microstructure pore size were also increased with enhancing of ionic strength, resulting in a significant decrease in the WH. The effective permeability coefficient (k1) and water flux coefficient (k2) of gels have a significant positive correlation with their network pore size, indicated that the regulation of WH of hydrogel mainly depended on controlling the pore size of its microstructure.

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.

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.

Insight into protein-starch ratio on the gelatinization and retrogradation characteristics of reconstituted rice flour.

Protein and starch are the two most abundant components in rice flour and play an important role in its physicochemical properties. Herein, the gelatinization and retrogradation properties of reconstituted rice flour (RCRF) composed of different protein-starch mass ratios were investigated. It was found that increasing the protein content from 0% to 8% will result in the gelatinization peak viscosity of the RCRF being reduced from 2198 ± 96.8 cp to 1754 ± 111.6 cp, the gelatinization temperature increased from 72.4 ± 0.4 °C to 75.6 ± 1.8 °C. In addition, the hardness of RCRF gels was increased after retrogradation, while a reduction in crystallinity was found depending on the increasing of protein content during storage. The increase of protein content could lead to the insufficient gelatinization of the RCRF, inhibiting the long-term retrogradation of flour. On the other hand, the water migration in the RCRF gels could be weakened with the protein addition, as well as the water distribution was more uniform and the gel shape could be moderately maintained. These results indicated that changes in protein-starch mass ratio have an important effect on the properties of the RCRF, especially gelatinization and retrogradation characteristics.

Binding interaction between ß-conglycinin/glycinin and cyanidin-3-O-glucoside in acidic media assessed by multi-spectroscopic and thermodynamic techniques.

The noncovalent binding mechanisms between cyanidin-3-O-glucoside (C3G) and two main soy protein fractions: ß-conglycinin (7S) and glycinin (11S) at pH 3.0 were investigated and compared. C3G modified the secondary structure of two fractions by increasing α-helix and random coil content while decreasing ß-sheet content. The binding of C3G also altered the tertiary structure and microenvironment of two fractions, demonstrated by synchronous and three-dimensional fluorescence spectra. Additionally, C3G binding reduced the surface hydrophobicity and thermostability of both 7S and 11S. Moreover, the fluorescence quenching results showed that the binding of C3G to two fractions were spontaneous complexation processes driven by electrostatic forces. The number of C3G bound per protein molecule (n) was near 1. The binding constant (Ka) was 2.41 (±0.42) × 104 M-1 for 11S and 0.81 (±0.01) × 104 M-1 for 7S at 298 K. 11S showed a stronger binding ability for C3G than 7S. These findings contribute to the knowledge of interactions between soy protein fractions and dietary polyphenols under acidic condition, and are beneficial for the application of soy protein-based products in foods.

Characteristic of interaction mechanism between ß-lactoglobulin and nobiletin: A multi-spectroscopic, thermodynamics methods and docking study.

Nobiletin (Nob) is a major component among the most reported polymethoxyflavones (PMFs), which possesses multiple efficacious healthcare activities. Owing to its high melting point and poor water solubility, the oral bioavailability of Nob needs to be improved via loading Nob on carriers. To take full advantage of Nob, the interaction mechanism between Nob and vehicles should be clarified. Herein, ß-lactoglobulin (ß-LG) was selected as the vehicle and further investigated the binding mechanism between Nob and ß-LG. The binding stoichiometry of complex was found to be 1:1 by analysis of intrinsic fluorescence experiment. The results also confirmed by isothermal titration calorimetry (ITC) measurement that the binding behavior between ß-LG and Nob was a spontaneously endothermic process driving mainly by hydrophobic interaction. Moreover, competitive binding and molecular docking method indicated the Nob was primary bound to internal calyx of ß-LG at neutral pH. UV spectrophotometry revealed that the solubility of Nob was enhanced to 3 times by forming complex. Furthermore, Nob could alter secondary structure of ß-LG by a transition from α-helix to ß-sheet and lead to small increase on surface hydrophobicity of ß-LG. This work will provide some valuable information on clarifying the interaction between protein and PMFs, which contributing to improve the poor bioavailability of PMFs.

Covalent Interaction between Rice Protein Hydrolysates and Chlorogenic Acid: Improving the Stability of Oil-in-Water Emulsions.

Protein hydrolysates, as surfactants, can scavenge radicals, but their poor distributions at the oil-water interface limit their storage stability. Therefore, we studied covalent interaction between rice protein hydrolysates and chlorogenic acid under alkaline conditions to improve the physical and oxidative stability of oil-in-water emulsions. Turbidity and particle size measurements demonstrated the formation of hydrolysates-chlorogenic acid complexes, and their covalent interaction resulted in the decrease and redshift of the fluorescence intensity. The emulsifying activity of the hydrolysates could be effectively improved after the covalent interaction with 0.025% chlorogenic acid. The modified emulsions possessed a notable physical stability according to the least changes in size (0.08 µm) and ζ-potential (3.34 mV) of the emulsion ( P > 0.05). Moreover, the covalent interaction endowed modified emulsions with high oxidative stability to effectively inhibit lipid oxidative deterioration during storage. The adsorption of hydrolysates to the emulsion interface was increased by the adequate addition of chlorogenic acid, which resulted in the oil droplet being surrounded by a thicker interfacial film. The covalent interaction between the protein hydrolysates and chlorogenic acid could be used to construct natural emulsion systems with a higher physical and oxidative stability during storage.

Effects of thermal sterilization on soy protein isolate/polyphenol complexes: Aspects of structure, in vitro digestibility and antioxidant activity.

The main purpose of this work was to investigate the influence of typical thermal sterilization approaches (pasteurization, high-temperature sterilization) on the structure, in vitro digestibility, and antioxidant activity of soy protein isolate (SPI)/black soybean seed coat extract (BE) complexes at pH 7.0. The results of zeta potential and particle size demonstrated that the addition of BE was contributed to inhibit protein thermal aggregation. Heat sterilization resulted in protein unfolding revealed by UV-Vis, circular dichroism, and fluorescence spectroscopy analysis. The increase of BE led to the reduction of fluorescence intensity and surface hydrophobicity of SPI. Moreover, the formation of SPI/BE complexes inhibited protein digestion in vitro, while thermal sterilization promoted protein digestion. The SPI/BE complexes showed a strong radical scavenging ability both before and after thermal treatment.

Enhancing the photostability and bioaccessibility of resveratrol using ovalbumin-carboxymethylcellulose nanocomplexes and nanoparticles.

The objective of this study was to investigate the impact of encapsulating resveratrol in ovalbumin (OVA)-carboxymethylcellulose (CMC) nanocomplexes or nanoparticles on its photostability and bioaccessibility. The nanocomplexes were formed by the electrostatic assembly between OVA and CMC, and the nanoparticles were fabricated through further heating the nanocomplexes at 90 °C for 30 min. The nanocomplexes and nanoparticles both presented a spherical morphology, and the nanoparticles exhibited larger average particle sizes and net zeta potential. The encapsulation efficiency and loading capacity were around 26% and 13 µg mg-1 for OVA/CMC nanocomplexes, and evidently increased to around 70% and 35 µg mg-1 for OVA/CMC nanoparticles, respectively. The major driving forces for resveratrol encapsulation were hydrogen bonding and hydrophobic interaction. Both the formulations could improve the photostability of trans-resveratrol when exposed to UV light, and the nanoparticles were more effective. Moreover, the release profile of resveratrol from the nanocapsules in the in vitro simulated gastrointestinal tract was greatly enhanced and could be well fitted using the Higuchi kinetic model and Korsmeyer-Peppas model, indicating a Fickian diffusion release mechanism. Compared to native resveratrol, the bioaccessibility of resveratrol embedded in nanocomplexes and nanoparticles was increased to 60% and 80%, respectively. These findings suggest that OVA/CMC nanocomplexes and nanoparticles have potential applications in the development of effective oral delivery systems of resveratrol as well as other lipophilic nutraceuticals into functional foods.

Effect of high intensity ultrasound on structure and foaming properties of pea protein isolate.

The effects of high intensity ultrasound (HIUS, 20 kHz, at varying amplitude 30%, 60%, 90% for 30 min) on structure and foaming properties of pea protein isolate (PPI) were investigated. No significant change was observed from the electrophoresis profiles and circular dichroism (CD) spectrum. Analyses of fluorescence spectroscopy and the amount of free sulfhydryl groups showed that HIUS induced protein molecular partial unfolding. Furthermore, HIUS decreased particle size of PPI and increased exposed hydrophobicity, resulting in a reduction of the surface tension at the air-water interface. Therefore, the foaming ability of PPI increased from 145.6% to 200.0%. The foaming stability increased from 58.0% to 73.3% with the increasing amplitude after 10 min though all reduced to 50.0% with the extension of time. That suggested that HIUS treatment has a potential to be implemented to modify foaming properties of PPI.

Emulsion stability and dilatational viscoelasticity of ovalbumin/chitosan complexes at the oil-in-water interface.

The contribution of the emulsion rheological properties and the viscoelastic of the interface adsorbed layer to the emulsification mechanism of ovalbumin (OVA)-chitosan (CS) mixtures were investigated. In comparison to the treatment with OVA alone and OVA/CS mixtures at pH 4.0, the addition of CS at pH 5.5 increased the size distribution of emulsion droplets with significant flocculation through polyelectrolyte bridging, remarkably enhancing the emulsions stability against gravity creaming after storage at 25 °C for 14 days. The dynamic rheological properties indicated that the formation of the complex at pH 5.5 increased the elastic modulus (G') and apparent viscosity (η∗) of the emulsions, which is useful for inhibiting creaming. Moreover, the complexation of OVA and CS at pH 5.5 increased the dilatational modulus (E), especially the elastic modulus (Ed), of the oil/water interfacial absorbed layer, which could reduce the droplet coalescence and therefore inhibit the growth of emulsion droplets.

Adsorption and Distribution of Edible Gliadin Nanoparticles at the Air/Water Interface.

Edible gliadin nanoparticles (GNPs) were fabricated using the anti-solvent method. They possessed unique high foamability and foam stability. An increasing concentration of GNPs accelerated their initial adsorption speed from the bulk phase to the interface and raised the viscoelastic modulus of interfacial films. High foamability (174.2 ± 6.4%) was achieved at the very low concentration of GNPs (1 mg/mL), which was much better than that of ovalbumin and sodium caseinate. Three stages of adsorption kinetics at the air/water interface were characterized. First, they quickly diffused and adsorbed at the interface, resulting in a fast increase of the surface pressure. Then, nanoparticles started to fuse into a film, and finally, the smooth film became a firm and rigid layer to protect bubbles against coalescence and disproportionation. These results explained that GNPs had good foamability and high foam stability simultaneously. That provides GNPs as a potential candidate for new foaming agents applied in edible and biodegradable products.

Nanogels fabricated from bovine serum albumin and chitosan via self-assembly for delivery of anticancer drug.

In this study, bovine serum albumin (BSA) and chitosan (CS) were used to prepare BSA-CS nanogels by a simple green self-assembly technique. Then the nanogels were successfully used to entrap doxorubicin hydrochloride (DOX) with an entrapment ratio of 46.3%, aiming to realize the slow-release effect and lower the cytotoxicity of DOX. The IC50 values of DOX-loaded BSA-CS (DOX-BSA-CS) and free DOX obtained by MTT assay in SGC7901 cells were 0.22 and 0.05µg/mL, respectively. The cytotoxicity of DOX significantly decreased within 24h after encapsulation by the nanogels, indicating that the loaded drug could slowly release within 24h and the BSA-CS was a good slow release system. The cellular uptake experiments indicated DOX-BSA-CS diffused faster into the cancer cell than the bare drug. The flow cytometry and TUNEL assay proved DOX-BSA-CS could induce a larger apoptosis proportion of gastric cancer cells 7901 than the bare drug and it is promising to be used for curing gastric cancer.

High intensity ultrasound modified ovalbumin: Structure, interface and gelation properties.

Influence of high intensity ultrasound (HIUS) on the structure and properties of ovalbumin (OVA) were investigated. It was found that the subunits and secondary structure of OVA did not change significantly with HIUS treatment from the electrophoretic patterns and circular dichroism (CD) spectrum. The amount of free sulfhydryl groups increased and intrinsic fluorescence spectra analysis indicated changes in the tertiary structure and partial unfold of OVA after sonication increased. Compared with the untreated OVA, HIUS treatment increased the emulsifying activity and foaming ability, and decreased interface tension (oil-water and air-water interface), which due to the increased surface hydrophobicity and decreased the surface net charge in OVA, while the emulsifying and foaming stability had no remarkable differences. The increased particle size may be attributed to formation of protein aggregates. Moreover, the gelation temperatures of HIUS-treated samples were higher than the untreated OVA according to the temperature sweep model rheology, and this effect was consistent with the increased in surface hydrophobicity for ultrasound treated OVA. These changes in functional properties of OVA would promote its application in food industry.