Effects of glycation method on the emulsifying performance and interfacial behavior of coconut globulins-fucoidan complexes

Insight into the oxidation mechanism of coconut globulin by atmospheric cold plasma focusing on side chain amino acids

Atmospheric cold plasma (ACP), a novel non-thermal processing technology, generates active substances that stimulate protein oxidation in protein-based foods. Nevertheless, the precise mechanism through which ACP initiates amino acid oxidation on protein side chains remains ambiguous. This study primarily aimed to elucidate the mechanism of ACP-induced oxidation of coconut globulin, focusing on the process of amino acid oxidation. Analysis of protein oxidation products indicated a positive correlation between the extent of protein oxidation and the voltage and duration of ACP treatment. By analyzing the composition of amino acids and active ingredients, the study identified that the most significant changes amino acids were methionine, cysteine, and arginine, and •OH was the primary free radicals. The findings from oxidation kinetics and dynamic simulation indicated that •OH predominantly oxidized methionine, followed by L-cysteine and L-arginine. These results offer theoretical framework for understanding protein oxidation by ACP and suggest potential applications in protein-based food.

Hyaluronic acid-decorated lipid nanocarriers as novel vehicles for curcumin: Improved stability, cellular absorption, and anti-inflammatory effects

This study aimed to investigate how hyaluronic acid interfacial decoration affects the stability, cellular absorption, and anti-inflammatory effects of curcumin-loaded nanostructured lipid carriers. Nanocarriers were synthesized with an ovalbumin single layer and ovalbumin/hyaluronic acid double, mixed, or conjugated layers. All nanocarriers were spherical (200-300 nm diameter), and their encapsulation efficiency exceeded 95 %. Among the layers, the conjugated one exhibited the highest elastic surface dilatational modulus of approximately 40 mN/m, and the longest curcumin half-life of 186.07 days at 4 °C. Spearman's correlation analysis showed a negative correlation (r = -0.6698) between the recrystallization index and curcumin stability. The layer's mechanical strength improved curcumin stability by preventing crystal transition. Hyaluronic acid decoration enhanced the curcumin uptake of Caco-2 cells by 1.96-2.48 folds. Among the layers, the conjugate one was the most effective because of its strong binding constant with the receptor. Hyaluronic acid decoration improved the anti-inflammatory effects of curcumin.

Improving the emulsifying properties and oil-water interfacial behaviors of chickpea protein isolates through Maillard reaction with citrus pectin

The limited adsorption capability of chickpea protein isolates (CPI) at the oil-water interface restricts its application in emulsions. This study aimed to improve the emulsifying properties and interfacial behaviors of CPI through Maillard reaction with citrus pectin (CP). The research findings showed that the covalent linking of CP with CPI caused the unfolding of the molecular structure of CPI, exposing more hydrophobic groups. Consequently, the CPI-CP conjugates exhibited improved emulsifying properties. Emulsions stabilized by CPI-CP conjugates after 12 h of glycosylation demonstrated the smallest droplet sizes (1.73 μm) and the highest negative zeta potentials (-54.7 mV). Glycosylation also improved the storage and environmental stability of these emulsions. Interfacial adsorption kinetics analysis revealed the lower interfacial tension (13.94 mN/m) and faster diffusion rates of the CPI-CP conjugates. Furthermore, interfacial dilatational rheology analysis indicated that the CPI-CP conjugates formed an interfacial layer with a higher viscoelastic modulus (33.214 mN/m) and predominant elastic behavior. The interfacial film of CPI-CP conjugates showed excellent resistance to amplitude and frequency variations, enhancing emulsion stability. Thus, this study demonstrates that moderate glycosylation enhances interfacial performances and improves emulsion stability of CPI, providing new insights into the mechanisms by which CPI stabilizes emulsions.

The composition, extraction, functional property, quality, and health benefits of coconut protein: A review

Coconut is widely appreciated for its distinctive flavor and is commonly utilized in the production of a variety of goods. Coconut protein, a by-product derived from coconut oil and coconut milk cake, is frequently underutilized or discarded. This study provides a comprehensive overview of the distribution and composition of coconut protein. Analyses reveal that coconut protein, specifically 11S globulin and 7S globulin, is predominantly found in coconut flesh. Furthermore, various extraction techniques for coconut protein, such as chemical, enzymatic, and physical methods, are discussed. The alkali dissolution and acid precipitation methods are widely utilized for extracting coconut protein, with the potential for enhancement through the incorporation of physical methods such as ultrasound. The evaluation of functional properties, quality, and health benefits of coconut protein is essential, given the limitations imposed by its solubility. Modification may be necessary to optimize its functional properties. Coconut presents a promising source of food protein, characterized by balanced amino acid composition, high digestibility, and low allergenic potential. In conclusion, this study provides a comprehensive overview of the extraction methods, functional properties, quality, and nutritional benefits of coconut protein, offering insights for potential future research directions in the field. Additionally, the information presented may serve as a valuable reference for incorporating coconut protein into plant-based food products.

Effect of non-covalent binding of tannins to sodium caseinate on the stability of high-internal-phase fish oil emulsions

In this study, we designed the noncovalent binding of sodium caseinate (SC) to tannic acid (TA) to stabilize high internal phase emulsions (HIPEs) used as fish oil delivery systems. Hydrogen bonding was the dominant binding force, followed by weak hydrophobic interaction and weak van der Waals forces, as demonstrated by FTIR, fluorescence spectroscopy, and molecular docking experiments, with a binding constant of 3.25 × 106, a binding site of 1.2, and a static quenching of the binding. Increasing SC:TA from SC to 2:1 decreased the particle size from 107.37 ± 10.66 to 76.07 ± 2.77 nm and the zeta potential from -6.99 ± 2.71 to -22 ± 2.42 mV. TA increased the interfacial tension of SC, decreased the surface hydrophobicity from 1.3 × 104 to 1.6 × 103 and improved the oxidation resistance of SC. The particle size of high internal phase emulsions stabilized by complexes with different mass ratios (SC:TA from 1:0 to 2:1) increased from 4.9 ± 0.02 to 12.9 μm, the potential increased from -32.37 ± 2.7 to -35.07 ± 2.58 mV, and the instability index decreased from 0.75 to 0.02. Thicker interfacial layers could be observed by laser confocal microscopy, and an increase in the storage modulus indicated a formation of a stronger gel network. SC:TA of 1:0 showed emulsion breakage after 14 d of storage at room temperature. SC:TA of 2:1 showed the lowest degree of oil-water separation after freeze-thaw treatment. Especially, the most stable high endo-phase emulsion (at SC:TA of 2:1) prepared at each mass ratio was selected for further stability exploration. The emulsion particle size increased only from 15.63 ± 0.06 to 22.27 ± 0.35 μm at salt ion concentrations of 50-200 mM and to 249.33 ± 31.79 μm at 300 mM. The instability index and storage modulus of the high endo-phase emulsions increased gradually with increasing salt ion concentrations. At different heating temperatures (55-85 °C), the instability index of the high internal phase emulsion gradually decreased and the storage modulus gradually increased. Meanwhile, at 50 °C for 15 d of accelerated oxidation, the content of hydroperoxide decreased from 53.32 ± 0.18 to 37.48 ± 0.77 nmol/g, about 29.7 %, and the thiobarbituric acid value decreased from 1.06 × 103 to 0.8 × 103, about 24.5 %, in the high endo-phase emulsions prepared by 2:1 SC:TA compared to the fish oils, and the SC-stabilized high endo-phase only emulsion broke at the sixth day of oxidation. From the above findings, it was concluded that the high internal phase emulsion prepared with SC:TA of 2:1 can be used as a good delivery system for fish oil.

Enhancement of hydrogen bonds between proteins and polyphenols through magnetic field treatment: Structure, interfacial properties, and emulsifying properties

In food systems, proteins and polyphenols typically coexist in a non-covalent manner. However, the inherent rigid structure of proteins may hinder the binding sites of polyphenols, thereby limiting the strength of their interaction. In the study, magnetic field (MF) treatment was used to enhance non-covalent interactions between coconut globulin (CG) and tannic acid (TA) to improve protein flexibility, enhancing their functional properties without causing oxidation of polyphenols. Based on protein structure results, the interaction between CG and TA caused protein structure to unfold, exposing hydrophobic groups. Treatment with a MF, particularly at 3 mT, further promoted protein unfolding, as evidenced by a decrease in α-helix structure and an increase in coil random. These structural transformations led to the exposure of the internal binding site bound to TA and strengthening the CG-TA interaction (polyphenol binding degree increased from 62.3 to 68.2%). The characterization of molecular forces indicated that MF treatment strengthened hydrogen bonding-dominated non-covalent interactions between CG and TA, leading to improved molecular flexibility of the protein. Specifically, at a MF treatment at 3 mT, CG-TA colloidal particles with small size and high surface hydrophobicity exhibited optimal interfacial activity and wettability (as evidenced by a three-phase contact angle of 89.0°). Consequently, CG-TA-stabilized high internal phase Pickering emulsions (HIPPEs) with uniform droplets and dense gel networks at 3 mT. Furthermore, the utilization of HIPPEs in 3D printing resulted in consistent geometric shapes, uniform surface textures, and distinct printed layers, demonstrating superior printing stability. As a result, MF treatment at 3 mT was identified as the most favorable. This research provides novel insights into how proteins and polyphenols interact, thereby enabling natural proteins to be utilized in a variety of food applications.

Dynamic interfacial adsorption and emulsifying performance of self-assembled coconut protein and fucoidan mixtures

The functional properties of protein are affected by their aggregation behavior and morphology. In this study, the self-assembled coconut protein aggregates with specific morphology, including small amorphous aggregates (WLA), spherical-like aggregates (SLA) and rod-like aggregates (RLA), were regulated to form. The self-assembled process resulted in a decrease in fluorescence intensity and an increase in the surface hydrophobicity of coconut protein. Fucoidan was added to improve the stability of protein solutions, and the interfacial adsorption behavior was evaluated by dilatational rheology analysis. The results showed that the aggregation state of coconut protein affected its ability to reduce surface tension, and the interfacial layers mainly exhibited elastic property at oil-water interface (tanφ < 0.5). For macroscale analysis, the emulsions based on self-assembled coconut protein exhibited smaller droplet size, better rheological properties and centrifugal stability, especially WLA and RLA. This study may provide a reference to inspire the utilization of self-assembled coconut protein in the food industry.

Preparation and Properties of Walnut Protein Isolate-Whey Protein Isolate Nanoparticles Stabilizing High Internal Phase Pickering Emulsions

To enhance the functional properties of walnut protein isolate (WalPI), hydrophilic whey protein isolate (WPI) was selected to formulate WalPI-WPI nanoparticles (nano-WalPI-WPI) via a pH cycling technique. These nano-WalPI-WPI particles were subsequently employed to stabilize high internal phase Pickering emulsions (HIPEs). By adjusting the mass ratio of WalPI to WPI from 9:1 to 1:1, the resultant nano-WalPI-WPI exhibited sizes ranging from 70.98 to 124.57 nm, with a polydispersity index of less than 0.326. When the mass ratio of WalPI to WPI was 7:3, there were significant enhancements in various functional properties: the solubility, denaturation peak temperature, emulsifying activity index, and emulsifying stability index increased by 6.09 times, 0.54 °C, 318.94 m2/g, and 552.95 min, respectively, and the surface hydrophobicity decreased by 59.23%, compared with that of WalPI nanoparticles (nano-WalPI), with the best overall performance. The nano-WalPI-WPI were held together by hydrophobic interactions, hydrogen bonding, and electrostatic forces, which preserved the intact primary structure and improved resistance to structural changes during the neutralization process. The HIPEs stabilized by nano-WalPI-WPI exhibited an average droplet size of less than 30 μm, with droplets uniformly dispersed and maintaining an intact spherical structure, demonstrating superior storage stability. All HIPEs exhibited pseudoplastic behavior with good thixotropic properties. This study provides a theoretical foundation for enhancing the functional properties of hydrophobic proteins and introduces a novel approach for constructing emulsion systems stabilized by composite proteins as emulsifiers.

Interfacial Behavior and Long-Term Stability of the Emulsions Stabilized by Sugar Beet Pectin-Ca2+ Complexes with Different Cross-Linking Degrees

Recent studies showed that sugar beet pectin exhibited more excellent emulsifying properties than traditional citrus peel pectin and apple pectin ascribed to the higher content of neutral sugar, protein, ferulic acid, and acetyl groups. It is precisely because of the extremely complex molecular structure of pectin that the emulsifying properties of the pectin-Ca2+ complex are still unclear. In this study, SBP-Ca2+ complexes with different cross-linking degrees were prepared. Subsequently, their interfacial adsorption kinetics, the resistance of interfacial films to external perturbances, and the long-term stability of the emulsions formed by these SBP-Ca2+ complexes were measured. The results indicated that the highly cross-linked SBP-Ca2+ complex exhibited slower interfacial adsorption kinetics than SBP alone. Moreover, compared with SBP alone, the oil-water interfacial film loaded by the highly cross-linked SBP-Ca2+ complex exhibited a lower elasticity and a poorer resistance to external perturbances. This resulted in a larger droplet size, a lower ζ-potential value, a larger continuous viscosity, and a worse long-term stability of the emulsion formed by the highly cross-linked SBP-Ca2+ complex. This study has very important guiding significance for deeply understanding the emulsification mechanism of the pectin-Ca2+ complex.