Effects of (+)-catechin on a rice bran protein oil-in-water emulsion: Droplet size, zeta-potential, emulsifying properties, and rheological behavior

Effect of phenolic compounds and hydroxyl content on the physicochemical properties of pine nut oil Pickering emulsions

BACKGROUND

For decades, pine nut oil Pickering emulsions have been stabilized using a covalent composite of two phenolic chemicals (tannic acid, TA; and gallic acid, GA) and whey protein isolate (WPI) following alkali treatment. Based on covalent composite particles being excellent sources of high-quality stabilizers, this research explored the influence of phenolic addition and hydroxyl content on stability, rheological parameters and characterization of Pickering emulsions.

RESULTS

Tannic acid was more effective in reducing the average particle size of the emulsion, which decreased from 479.4 ± 2.1 nm without addition to between 187.6 ± 5.9 and 368.2 ± 16.8 nm (P < 0.05). The potential values of all the emulsions were between -30 and -50 mV (except for the gallic acid addition of 2.5 g kg^-1 ). When the phenolic addition was 7.5 g kg^-1 , emulsions demonstrated the best emulsification ability. Pickering emulsion stabilized by WPI-TA and WPI-GA particles were successfully generated, according to confocal laser scanning microscopy. Rheological results showed that the increase of phenolic addition contributed to larger elastic modulus (G'), viscosity modulus (G″) and viscosity of emulsions, which was beneficial to the stability of emulsions.

CONCLUSION

Both phenolic compounds significantly improved the physicochemical stability of the emulsions (P < 0.05) and their oxidative stability. Covalently crosslinking phenolic compounds to proteins is a better method to prepare stable emulsions. It is more prominent that TA shows a more significant improvement in emulsion stability due to the number of hydroxyl groups it can provide. This research might serve as a theoretical foundation for enhancing the quality of pine nut oil-related products. © 2022 Society of Chemical Industry.

Effects of heat treatment and pH on the physicochemical and emulsifying properties of coconut (Cocos nucifera L.) globulins

The present study aimed to assess the effects of heat treatment (70-90 °C) and pH (pH 3-11) on the physicochemical, structural, and emulsifying properties of coconut globulins (CG). The results revealed that the emulsifying property was improved with increasing temperature due to the denaturation degree of CG. CG had a better emulsifying property at pH 3 but showed the worst emulsifying property at pH 5 due to its lowest solubility, surface hydrophobicity, and absolute value of zeta potential. The best emulsifying stability was detected at pH 11 with 90 °C heating. SDS-PAGE indicated that the formation of aggregates cross-linked by covalent bonds was the main reason for the better emulsion stability at pH 3 and pH 11 with 90 °C heating. The secondary structure showed that CG had more α-helix and β-turn contents as well as fewer β-sheet contents at pH 3 and pH 11 with 90 °C heating.

Succinylation Modified Ovalbumin: Structural, Interfacial, and Functional Properties

In this study, ovalbumin (OVA) was succinylated with the addition of different levels of succinic anhydride, and the structural and functional properties of succinylated OVA (SOVA) were investigated. SDS−PAGE and FTIR spectrum confirmed the covalent attachment of the succinyl group to OVA. Thermal stability and the absolute value of zeta potential (pH 6.0) of SOVA were enhanced by 14.90% and 76.77% higher than that of the native OVA (NOVA), respectively. Circular dichroism (CD) spectra demonstrated that the succinylation decreased the α−helix and increased β−sheet content to 21.31% and 43.28%, respectively. The content of free sulfhydryl groups increased and intrinsic fluorescence spectra suggested the SOVA became more unfolded and flexible as the degree of succinylation enhanced. Furthermore, succinylation effectively enhanced the solubility and decreased the interface tension (oil−water and air−water interface) of OVA. Compared to NOVA, the emulsifying activity and stability of SOVA were increased by 1.6 times and 1.2 times, respectively, and foaming capacity and stability were enhanced by 2.7 times and 1.5 times, respectively.

Fabrication and characterization of a cannabidiol-loaded emulsion stabilized by a whey protein-maltodextrin conjugate and rosmarinic acid complex

A cannabidiol (CBD)-loaded oil-in-water emulsion stabilized by a whey protein (WP)-maltodextrin (MD) conjugate and rosmarinic acid (RA) complex was fabricated, and its stability characteristics were investigated under various environmental conditions. The WP-MD conjugates were formed via dry-heating. The interaction between WP and MD was assessed by browning intensity, reduced amount of free amino groups, the formation of high molecular weight components in sodium dodecyl sulfate-PAGE, and changes in secondary structure of whey proteins. The WP-MD-RA noncovalent complex was prepared and confirmed by fluorescence quenching and Fourier-transform infrared spectroscopy spectra. Emulsions stabilized by WP, WP-MD, and WP-RA were used as references to evaluate the effect of WP-MD-RA as a novel emulsifier. Results showed that WP-MD-RA was an effective emulsifier to produce fine droplets for a CBD-loaded emulsion and remarkably improved the pH and salt stabilities of emulsions in comparison with WP. An emulsion prepared with WP-MD-RA showed the highest protection of CBD against UV and heat-induced degradation among all emulsions. The ternary complex kept emulsions in small particle size during storage at 4°C. Data from the current study may offer useful information for designing emulsion-based delivery systems which can protect active substance against environmental stresses.

High internal phase emulsions stabilized solely by sonicated quinoa protein isolate at various pH values and concentrations

In this study, stable high internal phase emulsions (HIPEs) constructed solely by sonicated quinoa protein isolate (QPI) at various pH values and protein concentrations (c) were constructed, and differences of HIPE microstructures at these conditions were discussed. HIPEs stabilized by QPI at pH 7.0, 9.0 possessed smaller droplet size (14-24 μm), smoother appearance, and higher physical stability which were caused by polyhedral framework microstructure. However, at acidic conditions, QPI aggregates filled in the gaps between droplets (30-52 μm) instead of adsorbing to oil-water interface, which decreased the stability. The solid-like viscoelasticity of HIPEs were enhanced when the c increased while the increment of pH value had the significant opposite effect (decreased from about G' 1000 Pa, G″ 280 Pa to G' 350 Pa, G″ 50 Pa) due to the microstructure difference. This study broadens the commercial applications of quinoa protein in novel food products like fat substitutes.

Effects of preheat treatment and polyphenol grafting on the structural, emulsifying and rheological properties of protein isolate from Cinnamomum camphora seed kernel

In this study, protein isolate (PI) and purified polyphenol extract (PPE) were prepared from Cinnamomum camphora seed kernel (CCSK). The effects of preheat treatment (50-90 °C) combined with polyphenol grafting (5 % PPE, w/w) on the structural, emulsifying and rheological properties of PI were investigated. Results demonstrated the preheat treatments at 80 and 90 °C significantly increased the extent of protein aggregation of PI. Fluorescence spectra and thermal behavior analysis revealed that preheat-treated PI exhibited more compact structure and higher thermal stability. Moreover, the emulsifying stability and apparent viscosity of PI were enhanced after preheat treatments at 50, 60 and 70 °C. After modification by PPE, the secondary structural changes of preheat-treated PI were confirmed by FTIR. PPE modification improved the thermal stability and antioxidant activities of preheat-treated PI. These results provide a novel way to combine the advantages of preheat treatment and polyphenol grafting in developing a novel protein ingredient.

Antioxidant and emulsifying properties of a galactose-rich heteropolysaccharide from Plinia cauliflora peels

In this study functional properties of a galactose-rich heteropolysaccharide (GH) were accessed. The bands of a galactose-rich polysaccharide were found in FTIR spectra, including those from the fingerprint region. GH was characterized as a dark-red material (L* 25.86 ± 0.75, a* 9.46 ± 1.01, b* 0.65 ± 0.14, Chroma 9.48 ± 1.02) with antioxidant activity of 21.5 ± 0.08, 12.1 ± 0.06 and 0.46 ± 0.04 mmol Trolox Eq mg^-1 GH in FRAP, DPPH and ABTS, respectively. GH presented 44.9% of esterification degree and 10.73 ± 0. 01 mg of GAE g^-1. The production parameters of GH emulsions (GH concentration, time and ultrasound power) were optimized using a 2³ Central Composite Rotatable Design (CCRD). Emulsion droplets presented particle size (d µm) varying from 0.823 ± 0.065 to 1.926 ± 0.151, polydispersity index (PDI) from 0.10 ± 0.05 to 0.40 ± 0.01 and zeta potential from -29.25 ± 3.98 to -33.75 ± 1.77. Finally, the high emulsifying activity (EA) (96.67%) and emulsion stability (ES) (97.44%) allow suggesting that GH is a promising polysaccharide for food applications.

Improved protective and controlled releasing effect of fish oil microcapsules with rice bran protein fibrils and xanthan gum as wall materials

This study aimed to prepare fish oil microcapsules by freeze-drying an emulsion co-stabilized by rice bran protein fibrils (RBPFs) and xanthan gum (XG) to improve the oxidation stability and controlled release effect. Emulsions stabilized either solely by RBPFs or unfibrillated rice bran protein (RBP) or by a combination of RBP and XG were also fabricated as microcapsule templates for comparison. The rheological properties, particle size, and zeta potential of the emulsions were examined. In addition, the characteristics of the fish oil microcapsules such as surface oil content, encapsulation efficiency, water activity, moisture content, morphological structure, oxidation stability, and digestive performance were also assessed. The rheological properties revealed that the addition of XG increased the storage modulus of the emulsion and reduced the loss modulus and apparent viscosity. At shear rates of 0-100 s^-1, the fish oil emulsion did not exhibit any gel properties or shear thinning. Fibrillation increased the particle size of the fish oil emulsion, whereas adding XG reduced the droplet size. The combination of RBP fibrillation and XG addition provided the highest encapsulation efficiency for fish oil. Fibrillation reduced the water activity and moisture content of the fish oil microcapsules. The anisotropy of the fibrils and the high viscosity of XG produced a layer of wrapping on the continuous heterogeneous surface of the freeze-dried powder particles. RBPF/XG microcapsules stored at 45 °C for 1 month had the lowest peroxide value and thiobarbituric acid value, the lowest surface oil content, and the lightest yellowness. These results suggest that the combination of RBPFs and XG provides better encapsulation and protective effects for fish oil microcapsules. Upon simulated digestion, the microcapsules containing XG and RBPFs exhibited a more favorable controlled release of free fatty acids. These findings indicate that microcapsules formed from emulsions co-stabilized by XG and RBPFs are suitable for encapsulating fish oil in functional foods.

Ovalbumin/carboxymethylcellulose colloids: Particle compactness and interfacial stability

A protein/polysaccharide colloidal particle was prepared via combined complex coacervation and heat-induction. When the ratio of ovalbumin (OVA) to carboxymethylcellulose (CMC) was at 1:2, loose flexible particles (low D_f) with low surface hydrophobicity were obtained. Conversely, dense and compact particles (high D_f) were easily formed at a higher OVA/CMC ratio. Only in the appropriate OVA/CMC ratio, pH will have a greater impact on the colloidal particles. At the pH value of 4.4, the OVA/CMC ratio had a greater impact on the colloidal particles compared to pH. The emulsion stabilized by loose particles had a mean particle size of 3888 nm and was easily flocculated and creamed. On the other hand, compact particles formed a stable emulsion, which had a higher exponent of Δr² (0.867) and could resist flocculation during the 7 days storage. As such, the results showed that stable emulsion could be realized by utilizing compact particles as emulsifiers.

Improved effect of flaxseed gum on the weakened gelling properties of myofibrillar protein induced by catechin

The effect of flaxseed gum (FG) on the weakened gelling properties of myofibrillar proteins (MP) induced by catechin was investigated. Different levels of FG and catechin were incorporated into MP and the chemical changes of MP were studied; MP emulsions and gels with different levels of FG and catechin were prepared and their properties were studied. Catechin promoted the loss of thiol and the exposure of the hydrophobic groups of MP and increased the particle size and apparent viscosity of emulsions, resulting in a poor gel network. The incorporation of FG enhanced the gel strength, water holding capacity and dynamic rheological properties, which might be attributed to the formation of uniform and stabilized emulsions with high apparent viscosity and the enhanced disulfide cross-linking and hydrophobic interactions during heat-induced gelation. FG could be a potential approach in overcoming the deterioration of protein gels caused by catechin.

Interaction of lentil protein and onion skin phenolics: Effects on functional properties of proteins and in vitro gastrointestinal digestibility

The effect of protein-phenolic interactions on the functional properties of lentil protein and in vitro gastrointestinal digestibility in different systems (extract solution, protein-phenolic solution, and emulsion) was studied. The presence of phenolic compounds negatively affected the foaming and emulsion properties of lentil protein. During in vitro gastrointestinal digestion, total phenolic content (TPC) and antioxidant capacity of the samples were decreased with the presence of lentil protein at the initial phase, however, they were found to be the highest in emulsions at the intestinal phase. The amount of protocatechuic acid and phenolic acid derivative was increased at the intestinal phase, while that of other phenolic compounds was decreased. Quercetin was not detected at the intestinal phase in all systems, while its glycoside derivatives were determined, which were the highest in emulsions. Anthocyanins were also the highest in extract solution among all systems. Protein-phenolic interactions had a significant effect on functional properties of lentil proteins, and bioaccessibility or antioxidant capacity of phenolic compounds.

Lipid oxidation and in vitro digestion of pickering emulsion based on zein-adzuki bean seed coat polyphenol covalent crosslinking nanoparticles

This study first used adzuki bean seed coat polyphenol (ABSCP) to modify zein and form covalent nanoparticles (ZAP) and used ZAP as an emulsifier to stabilize Pickering emulsion (ZAE). The results showed that the ratio of zein-ABSCP controlled the physicochemical properties of the two compounds. ZAP could be absorbed on the water-oil surface and stabilized ZAE, which presented as a non-Newtonian fluid state with good rheological properties. The addition of ABSCP inhibited lipid oxidation in a dose-dependent manner, as verified through the analysis of accelerated oxidation experiments (50 °C, 20 days). In in vitro gastrointestinal digestion of ZAE showed that free fatty acids (FFA) release gradually decreased with ABSCP concentration increasing. Moreover, ABSCP gave ZAE a strong red-yellow color, which allowed ZAE to be used for specific applications (e.g., natural pigments). Our findings make it feasible to develope functional food and food-grade delivery systems made of protein-plant polyphenols nanoparticles.

Soy Protein Isolate/Sodium Alginate Microparticles under Different pH Conditions: Formation Mechanism and Physicochemical Properties

The effects of sodium alginate (SA) and pH value on the formation, structural properties, microscopic morphology, and physicochemical properties of soybean protein isolate (SPI)/SA microparticles were investigated. The results of ζ-potential and free sulfhydryl (SH) content showed electrostatic interactions between SPI and SA, which promoted the conversion of free SH into disulfide bonds within the protein. The surface hydrophobicity, fluorescence spectra, and Fourier transform infrared spectroscopy data suggested that the secondary structure and microenvironment of the internal hydrophobic groups of the protein in the SPI/SA microparticles were changed. Compared with SPI microparticles, the surface of SPI/SA microparticles was smoother, the degree of collapse was reduced, and the thermal stability was improved. In addition, under the condition of pH 9.0, the average particle size of SPI/SA microparticles was only 15.92 ± 0.66 μm, and the distribution was uniform. Rheological tests indicated that SA significantly increased the apparent viscosity of SPI/SA microparticles at pH 9.0. The maximum protein solubility (67.32%), foaming ability (91.53 ± 1.12%), and emulsion activity (200.29 ± 3.38 m²/g) of SPI/SA microparticles occurred at pH 9.0. The application of SPI/SA microparticles as ingredients in high-protein foods is expected to be of great significance in the food industry.

Effect of ultrasonic power on the emulsion stability of rice bran protein-chlorogenic acid emulsion

In this study, rice bran protein-chlorogenic acid (RBP-CA) emulsion was subjected to an ultrasonic-assisted treatment technique. The encapsulation efficiency and loading capacity of chlorogenic acid (CA), and the morphology, particle size, zeta (ζ)-potential, atomic force microscopy image, viscosity, turbidity, and interfacial protein content of the emulsion under different ultrasonic power were investigated. The results revealed that the emulsion exhibited an encapsulation efficiency and loading capacity of 86.26 ± 0.11% and 17.25 ± 0.06 g/100 g, respectively, at an ultrasonic power of 400 W. In addition, the size of the emulsion droplets decreased and became more evenly distributed. Furthermore, the viscosity of the emulsion decreased significantly, and it exhibited a turbidity and interfacial protein content of 24,758 and9.34 mg/m², respectively. Next, the storage, oxidation, thermal, and salt ion stabilities of the emulsion were evaluated. The results revealed that the ultrasonic-assisted treatment considerably improved the stability of the emulsion.

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

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

Effect of high-intensity ultrasound on the physicochemical properties, microstructure, and stability of soy protein isolate-pectin emulsion

In this study, an emulsion stabilized by soy protein isolate (SPI)-pectin (PC) complexes was prepared to investigate the effects of high-intensity ultrasound (HIU) treatment (150-600 W) on the physicochemical properties, microstructure, and stability of emulsions. The results found that the emulsion treated at 450 W showed the best emulsion stability index (ESI) (25.18 ± 1.24 min), the lowest particle size (559.82 ± 3.17 nm), the largest ζ-potential absolute value (16.39 ± 0.18 mV), and the highest adsorbed protein content (27.31%). Confocal laser scanning microscopy (CLSM) and atomic force microscopy (AFM) revealed that the emulsion aggregation was significantly improved by ultrasound treatment, and the average roughness value (Rq) was the smallest (10.3 nm) at 450 W. Additionally, HIU treatment reduced the interfacial tension and apparent viscosity of the emulsion. Thermal stability was best when the emulsion was treated at 450 W, D43 was minimal (907.95 ± 31.72 nm), and emulsion separation also improved. Consequently, the creaming index (CI) was significantly decreased compared to the untreated sample, indicating that the storage stability of the emulsion was enhanced.

Effects of High Hydrostatic Pressure Pretreatment on the Functional and Structural Properties of Rice Bran Protein Hydrolysates

Rice bran protein (RBP) hydrolysis was conducted after high hydrostatic pressure (HHP) pretreatment. The structural and functional properties of HHP-pretreated rice bran protein hydrolysates (RBPH) were investigated. HHP pretreatments were conducted at 100, 200, and 300 MPa; then, enzymatic hydrolysis at atmospheric pressure was performed using trypsin. An RBPH sample that had not been pretreated by HHP was used as a control. Free sulfhydryl (SH) content, SDS-PAGE profiles, high-performance size exclusion chromatography (HPSEC), Fourier transform infrared (FTIR) spectrum, scanning electron microscopy (SEM), intrinsic fluorescence spectrum, solubility, and emulsifying and foaming properties were evaluated. Changes in particle size and ζ-potential were monitored. Compared with the control, the results of solubility, the emulsifying activity index (EAI) and the emulsifying stability index (ESI) increased significantly (p < 0.05) at 200 MPa. The content of free SH increased significantly (p < 0.05) at 100 MPa. FTIR spectrum and fluorescence analysis confirmed the changes in the secondary and tertiary structures. The experimental results indicated that the structural and functional properties of HHP-pretreated RBPH improved.

Effect of high intensity ultrasound on the structure and solubility of soy protein isolate-pectin complex

In this study, a soy protein isolate (SPI)-pectin (PC) complex was prepared, and the effects of different high intensity ultrasound (HIU) powers on the structure and solubility of the complex were studied. Fourier transform infrared (FTIR) spectroscopy analysis exhibited that with increasing HIU power, the α-helix content of the SPI in the complex was significantly reduced, and the random coil content increased; however, an opposite trend appeared after higher power treatments. Fluorescence spectra showed that HIU treatment increased the fluorescence intensity of the complex, and the surface hydrophobicity was increased. The trend of the protein structure studied by Raman spectroscopy was similar to that of FTIR and fluorescence spectroscopy. When the HIU treatment was performed for 15 min and at 450 W power, the particle size of the complex was 451.85 ± 2.17 nm, and the solubility was 89.04 ± 0.19 %, indicating that the HIU treatment caused the spatial conformation of the protein to loosen and improved the functional properties of the complex. Confocal laser scanning microscopy (CLSM) revealed that the complex after HIU treatment exhibited improved dispersibility in water and smaller particle size. Gel electrophoresis results indicated that HIU treatment did not affect the protein subunits of the complex. Therefore, the selection of a suitable HIU treatment power can effectively improve the structural properties and solubility of SPI in the complex, and promote the application of the SPI-PC complex in food processing and industries.

Recent Progress on Protein-Polyphenol Complexes: Effect on Stability and Nutrients Delivery of Oil-in-Water Emulsion System

Oil-in-water emulsions are widely encountered in the food and health product industries. However, the unsaturated fatty acids in emulsions are easily affected by light, oxygen, and heat, which leads to oxidation, bringing forward difficulties in controlling emulsion quality during transportation, storage, and retail. Proteins are commonly used as emulsifiers that can enhance the shelf, thermal and oxidation stability of emulsions. Polyphenols are commonly found in plants and members of the family have been reported to possess antioxidant, anticancer, and antimicrobial activities. Numerous studies have shown that binding of polyphenols to proteins can change the structure and function of the latter. In this paper, the formation of protein-polyphenol complexes (PPCs) is reviewed in relation to the latters' use as emulsifiers, using the (covalent or non-covalent) interactions between the two as a starting point. In addition, the effects polyphenol binding on the structure and function of proteins are discussed. The effects of proteins from different sources interacting with polyphenols on the emulsification, antioxidation, nutrient delivery and digestibility of oil-in-water emulsion are also summarized. In conclusion, the interaction between proteins and polyphenols in emulsions is complicated and still understudied, thereby requiring further investigation. The present review results in a critical appraisal of the relevant state-of-the-art with a focus on complexes' application potential in the food industry, including digestion and bioavailability studies.

Effect of ultrasound on the properties of rice bran protein and its chlorogenic acid complex

Ultrasound technology was used to treat rice bran protein (RBP), and the structural and functional properties of ultrasonically treated RBP (URBP) and its chlorogenic acid (CA) complex were studied. When ultrasonic power of 200 W was applied for 10 min, the maximum emission peak λ_max of the URBP-CA complex in the fluorescence spectrum was red-shifted by 3.6 nm compared to that of the untreated complex. The atomic force microscope (AFM) analysis indicated that the surface roughness of the complex was minimized (3.89 nm) at the ultrasonic power of 200 W and treatment time of 10 min. Under these conditions, the surface hydrophobicity (H₀) was 1730, the contents of the α-helix and β-sheet in the complex were 2.97% and 6.17% lower than those in the untreated sample, respectively, the particle size decreased from 106 nm to 18.2 nm, and the absolute value of the zeta-potential increased by 11.0 mV. Therefore, ultrasonic treatment and the addition of CA changed the structural and functional properties of RBP. Moreover, when ultrasonic power of 200 W was applied for 10 min, the solubility, emulsifying activity index (EAI), and emulsion stability index (ESI) were 68%, 126 m²/g, and 37 min, respectively.

Self-Assembled Micellar Nanoparticles by Enzymatic Hydrolysis of High-Density Lipoprotein for the Formation and Stability of High Internal Phase Emulsions

In this study, the influence of pH on the conformational state of EHT, which was obtained from the enzymatic hydrolysis of trypsin, and the stabilizing properties of high internal phase emulsions have been demonstrated. Critical micelle concentration and transmission electron microscopy results exhibited the formation of micellar nanoparticles with mean diameters ranging from 108 to 1359.5 nm. The results of solubility, surface hydrophobicity, and conformations indicated that EHT tended to act as particulate emulsifiers at pH 3, 5, and 7, while at alkaline pH, it was more like a polymeric emulsifier, which could be proven by confocal laser scanning microscopy. The EHT at pH 7 exhibited better stabilizing properties than those at pH 9 and 11 as influenced by storage, temperature, and ionic strength. These findings might be of great importance for broadening the range of sustainable applications of amphiphilic peptides in foods and pharmaceuticals.

Characterization of the structure and properties of the isolating interfacial layer of oil-water emulsions stabilized by soy hull polysaccharide: Effect of pH changes

The effect of pH on the microstructure and properties of the soy hull polysaccharide interfacial layer was determined. The particle size at pH 2.0 was the largest (36.7 μm), whereas the absolute ζ-potential was the smallest. The protein content was the lowest at pH 2.0 and 9.0 and peaked around pH 4.0-5.0 (77.7%). The ordered secondary protein structure content under low pH conditions was greater than that under high pH conditions and the stability of the interfacial layer was higher at high pH, whereas the emulsion viscosity decreased by two orders of magnitude between pH 2.0 and 9.0. It appears that low pH reduced the thermal stability and increased the apparent viscosity of the emulsion by increasing the structural order of the protein in the interfacial layer. These findings lay the foundation for future work to reveal the key components and characteristic structures of soy hull polysaccharide that affect interfacial stability.

Covalent Interaction between High Hydrostatic Pressure-Pretreated Rice Bran Protein Hydrolysates and Ferulic Acid: Focus on Antioxidant Activities and Emulsifying Properties

Rice bran protein hydrolysates (RBPH) pretreated with high hydrostatic pressure (HHP) covalently interacted with ferulic acid (FA) (0.5 to 2.5 mg/mL) under alkaline conditions. The structural and functional properties of the conjugates were investigated. The results revealed that the FA binding equivalent on RBPH increased from 6.03 to 207.64 nmol/mg. FTIR spectral analysis indicated that the content of α-helix increased, whereas the contents of β-sheet, β-turn, and random coil decreased. The surface hydrophobicity (H₀) of RBPH increased, the fluorescence intensity decreased, and the tertiary structure changed because of covalent interactions between RBPH and FA. The emulsifying activity index of RBPH-FA (1.5 mg/mL) was 35.10% higher than that of the control, whereas FA concentrations higher than 1.5 mg/mL had a negative effect on emulsifying properties. RBPH-FA (2.5 mg/mL) exhibited the strongest antioxidant activity. This study provides a new reference for the application of RBPH-FA conjugates in food processing.

Hemp (Cannabis sativa L.) Seed Protein-EGCG Conjugates: Covalent Bonding and Functional Research

In order to make HPI have a wide application prospect in the food industry, we used EGCG to modify HPI. In this study, we prepared different concentrations (1, 2, 3, 4, and 5 mM) of (-)-epigallocatechin gallate (EGCG) covalently linked to HPI and use methods such as particle size analysis, circular dichroism (CD), and three-dimensional fluorescence spectroscopy to study the changes in the structure and functional properties of HPI after being covalently combined with EGCG. The particle size data indicated that the covalent HPI-EGCG complex was larger than native HPI, and the particle size was mainly distributed at about 200 μm. CD and three-dimensional fluorescence spectroscopy analyses showed that the conformation of the protein was changed by conjugation with EGCG. The β-sheet content decreased from 82.79% to 66.67% after EGCG bound to the protein, and the hydrophobic groups inside the protein were exposed, which increased the hydrophobicity of the protein and changed its conformation. After HPI and 1 mM of EGCG were covalently bonded, the solubility and emulsifying properties of the covalent complex were improved compared with native HPI. These results indicated that HPI-EGCG conjugates can be added in some foods.

Effects of insoluble dietary fiber and ferulic acid on the quality of steamed bread and gluten aggregation properties

The effects of insoluble dietary fiber (IDF) and ferulic acid (FA) on steamed bread quality and gluten aggregation properties were investigated. IDF and FA increased the hardness and decreased the specific volume of steamed bread, except for 0.3 g of FA. Compared to the control sample, the hardness of steamed bread with 0.3 g of FA decreased by 36%, and the specific volume increased by 10.91%. FA promoted gluten aggregation through a cross-linking reaction because the sodium dodecyl sulfate extractable protein (SDSEP) of gluten with 1.8 g of FA decreased by 61.32% compared to the control sample under non-reducing condition. The ζ-potential of gluten during the proofing and steaming stages decreased by 46.64% and 68.10% with the increase in IDF, which showed that IDF promoted gluten aggregation by reducing the electrostatic repulsion. Gluten aggregation caused by IDF and FA could be the main reason for steamed bread deterioration.

Effect of Ginger on Chemical Composition, Physical and Sensory Characteristics of Chicken Soup

In order to investigate the effect of ginger on taste components and sensory characteristics in chicken soup, the content of amino acids, organic acids, 5′-nucleotides, and mineral elements were determined in chicken soup sample. With the ginger added, free amino acids in chicken soup obviously increased and exceeded the total amounts in ginger soup and chicken soup. The content of glutamic acid (122.74 μg/mL) was the highest among 17 free amino acids in ginger chicken soup. Meanwhile, six organic acids detected in chicken soup all obviously increased, among which lactic acid (1523.58 μg/mL) and critic acid (4692.41 μg/mL) exceeded 1000 μg/mL. The content of 5′-nucleotides had no obvious difference between ginger chicken soup and chicken soup. Compared with chicken soup, ginger chicken soup had a smaller particle size (136.43 nm) and color difference (79.69), but a higher viscosity. With ginger added in chicken soup, the content of seven mineral elements was reduced, and the content of total sugar increased. Results from an electronic tongue indicated a difference in taste profiles among the soups. The taste components and sensory quality of chicken soup were obviously affected by adding the ginger.

Impact of Tetrapeptide-FSEY on Oxidative and Physical Stability of Hazelnut Oil-In-Water Emulsion

This study investigates the antioxidant behaviors of a hazelnut tetrapeptide, FSEY (Phe-Ser-Glu-Tyr), in an oil-in-water emulsion. The emulsion was prepared with stripped hazelnut oil at a ratio of 10%. O/W emulsions, both with and without antioxidants (FSEY and TBHQ), were incubated at 37 °C. The chemical stabilities, including those of free radicals and primary and secondary oxidation productions, along with the physical stabilities, which include particle size, zeta-potential, color, pH, and ΔBS, were analyzed. Consequently, FSEY displayed excellent antioxidant behaviors in the test system by scavenging free lipid radicals. Both primary and secondary oxidation products were significantly lower in the FSEY groups. Furthermore, FSEY assisted in stabilizing the physical structure of the emulsion. This antioxidant could inhibit the increase in particle size, prevent the formation of creaming, and stabilize the original color and pH of the emulsion. Consequently, FSEY may be an effective antioxidant additive to use in emulsion systems.