Effect of chitosan oligosaccharide glycosylation on the emulsifying property of lactoferrin

Agar-gelatin Maillard conjugates used for Pickering emulsion stabilization

A few protein- and polysaccharide-based particles have shown promising potential as stabilizers in multi-phase food systems. By incorporating polymer-based particles and modifying the wettability of colloidal systems, it is possible to create particle-stabilized emulsions with excellent stability. A Pickering emulsifier (AGMs) with better emulsifying properties was obtained by the Maillard reaction between acid-hydrolysed agar and gelatin. Laser confocal microscopy imaging revealed that AGMs particles can be used as solid emulsifiers to produce a typical O/W Pickering emulsion, with AGMs adsorbing onto the droplet surface to form a dense interfacial layer. Cryo-scanning electron microscopy analysis showed that AGMs self-assembled into a three-dimensional network structure, which prevented droplets aggregation through strong spatial site resistance, contributing to emulsion stabilization. These emulsions exhibited stability within a pH range of 1 to 11, NaCl concentrations not exceeding 300 mM, and at temperatures below 80 °C. The most stable emulsion oil-water ratio was 6:4 at a particle concentration of 0.75 % (w/v). AGMs-stabilized Pickering emulsion was utilized to create a semi-solid mayonnaise as a replacement for hydrogenated oil. Rheological analysis demonstrated that low-fat mayonnaise stabilized with AGMs exhibited similar rheological behavior to traditional mayonnaise, offering new avenues for the application of Pickering emulsions in the food industry.

Conjugation of chitopentaose with β-lactoglobulin using Maillard reaction, and its effect on the allergic desensitization in vivo

The conjugation of chitopentaose (CHP) on β-lactoglobulin (βLg) via Maillard reaction was used to desensitize βLg. The stable βLg-CHP conjugate (βC-4) was formed at 4 h incubation, which contains 5 CHP attached molecules and a conjugated degree of 42 %. The conjugation promoted the thermal stability and emulsifying properties of βLg, and inhibited the immunoglobulin E (IgE) combining capacity by decreasing the content of β-sheet in βLg. Moreover, βLg-CHP conjugates were imparted with anti-oxidant properties and anti-inflammatory activities. Further, the combined action of inhibited IgE combining capacity and anti-inflammatory activities improved the allergy desensitization in βLg sensitized mice. The results showed that overexpressed IgE and inflammatory factors, unbalanced Th1-/Th2- immune cytokines were significantly attenuated after βLg was conjugated with CHP, avoiding the inflammatory lesions in spleen and colon. Additionally, the adverse changes in gut microbiota were alleviated in βC-4 group with a decrease of Bacteroidetes and increase of Firmicutes at phylum level and the probiotic bacteria of Lactobacillaceae was significantly improved at the family level. Thus, the conjugation of CHP can desensitize allergic reaction caused by βLg.

Glycation-induced enhancement of yeast cell protein for improved stability and curcumin delivery in Pickering high internal phase emulsions

Pickering high internal phase emulsions (HIPEs) have gained significant attention for various applications within the food industry. Yeast cell protein (YCP), derived from spent brewer's yeast, stands out as a preferred stabilizing agent due to its cost-effectiveness, abundance, and safety profile. However, challenges persist in utilizing YCP, notably its instability under high salt concentration, thermal processing, and proximity to its isoelectric point. This study aimed to enhance YCP's emulsifying properties through glycation with glucose and evaluate its efficacy as a stabilizer for curcumin (CUR)-loaded HIPEs. The results revealed that glycation increased YCP's surface hydrophobicity, exposing hydrophobic groups. This augmentation, along with steric hindrance from grafted glucose molecules, improved emulsifying properties, resulting in a thicker interfacial layer around oil droplets. This fortified interfacial layer, in synergy with steric hindrance, bolstered resistance to pH changes, salt ions, and thermal degradation. Moreover, HIPEs stabilized with glycated YCP exhibited reduced oxidation rates and improved CUR protection. In vitro digestion studies demonstrated enhanced CUR bioaccessibility, attributed to a faster release of fatty acids. This study underscores the efficacy of glycation as a strategic approach to augment the applicability of biomass proteins, exemplified by glycated YCP, in formulating stable and functional HIPEs for diverse food applications.

Investigation of structural and physicochemical properties of microcapsules obtained from protein-polysaccharide conjugate via the Maillard reaction containing Satureja khuzestanica essential oil

In this study, some common proteins including, whey protein isolate (WPI), soy protein isolate (SPI), and gelatin (G) conjugated with maltodextrin (MD) via Maillard reaction and were then used to encapsulate Satureja khuzestanica essential oil (SKEO). The higher glycation degree was obtained at a pH of 9 and 3 h of heating at 60 °C for SPI and WPI, and 90 °C for G. The results of FTIR and intrinsic fluorescence test showed the possibility of covalent binding formation between proteins and maltodextrin. The encapsulation efficiencies were obtained about 83.84 %, 88.95 %, and 89.27 % for MD-SPI, MD-G, and MD-WPI, respectively. Moreover, the Maillard reaction-based microcapsules had higher antioxidant activity than the physical mixture of protein-polysaccharide. The addition of SKEO to microcapsules improved antimicrobial activity. The results of this study demonstrated that MD-WPI and MD-G, as encapsulating materials, can be used to enhance the physiochemical properties of microcapsules loaded with SKEO.

Low molecular weight chitosan oligosaccharides form stable complexes with human lactoferrin

Proteins in tears, including human lactoferrin (HLF), can be deposited and denatured on contact lenses, increasing the risk of microbial cell attachment to the lens and ocular complications. The surfactants currently used in commercial contact lens care solutions have low clearance ability for tear proteins. Chitosan oligosaccharide (COS) binds to a variety of proteins and has potential for use in protein removal, especially in contact lens care solutions. Here, we analyzed the interaction mechanism of COSs hydrolyzed from chitosan from different resources with HLF. The molecular weights (MWs) and concentrations of COSs were key factors for the formation of COS-HLF complexes. Lower MWs of COSs could form more stable COS-HLF complexes. COS from Aspergillus ochraceus had a superior effect on HLF compared with COS from shrimp and crab shell with the same MWs. In conclusion, COSs could bind to and cause a conformational change in HLF. Therefore, COSs, especially those with low MWs, have potential as deproteinizing agents in contact lens care solution.

Modulation of physicochemical properties of lipid droplets using soy protein isolate and lactoferrin interfacial coatings

In order to improve the physicochemical stability of soy protein isolate (SPI) emulsion, lactoferrin (LF) was used to modify the interface layer. The stable multilayer emulsion can be formed when the content of lactoferrin is 0.5% at pH 5. The emulsion with good stability was at pH 3-7, and it was also stable to temperature change. The FFAs release of SPI emulsion and LF-SPI emulsion was 103.9% and 103.7%, respectively. The results showed that the lactoferrin layer did not hinder the digestion of oil and the bioaccessibility of carotenoids, but lactoferrin layer improved the physicochemical stability of SPI emulsions. This work provides information valuable in the design of emulsion formulations for applications in the food, pharmaceutical, and personal care industries.

Dynamic microfluidic-assisted transglutaminase modification of soy protein isolate-chitosan: Effects on structural and functional properties of the adduct and its antioxidant activity after in vitro digestion

In this study, soy protein isolate (SPI)-chitosan (CS) adducts were prepared by using dynamic microfluidic-assisted transglutaminase (TGase) modification. It was shown that the solubility and degree of binding of SPI-CS adducts prepared by dynamic microfluidic-assisted TGase modification were better. After the samples were treated twice at 400 bar, the degree of binding for SPI-CS adducts increased to 31.97 ± 1.31%, and the solubility increased to 66.25 ± 1.10%. With the increase of microfluidic pressure, the exposed free sulfhydryl groups increased, the particle size reduced, and the surface hydrophobicity first increased and then decreased. Under the action of the pressure generated by microfluidics, the structure of the protein in the SPI-CS adduct was unfolded and transformed from an ordered structure to a disordered one. The SPI-CS adducts prepared with assisted dynamic microfluidic treatment showed significantly higher ABTS radical scavenging rate, DPPH radical scavenging rate and reducing power after in vitro digestion compared with that of SPI-CS adducts prepared with TGase alone. This result indicated that appropriate dynamic microfluidic treatment improved the structural and functional properties of TGase-modified SPI-CS adducts and significantly increased the antioxidant activity after in vitro digestion.

Insights into the Mechanism Underlying the Influence of Glycation with Different Saccharides and Temperatures on the IgG/IgE Binding Ability, Immunodetection, In Vitro Digestibility of Shrimp (Litopenaeus vannamei) Tropomyosin

Tropomyosin (TM) is a heat-stable protein that plays a crucial role as a major pan-allergen in crustacean shellfish. Despite the high thermal stability of the TM structure, its IgG/IgE binding ability, immunodetection, and in vitro digestibility can be negatively influenced by glycation during food processing, and the underlying mechanism remains unclear. In this study, TM was subjected to glycosylation using various sugars and temperatures. The resulting effects on IgG/IgE-binding capacity, immunodetection, and in vitro digestibility were analyzed, meanwhile, the structural alterations and modifications using spectroscopic and LC-MS/MS analysis were determined. Obtained results suggested that the IgG/IgE binding capacity of glycosylated TM, immunodetection recovery, and in vitro digestibility were significantly reduced depending on the degree of glycosylation, with the greatest reduction occurring in Rib-TM. These changes may be attributable to structural alterations and modifications that occur during glycosylation processing, which could mask or shield antigenic epitopes of TM (E3: 61-81, E5b: 142-162, and E5c: 157-183), subsequently reducing the immunodetection recognition and digestive enzyme degradation. Overall, these findings shed light on the detrimental impact of glycation on TMs potential allergenicity and digestibility immunodetection and provide insights into the structural changes and modifications induced by thermal processing.

Advances in preparation and application of food-grade emulsion gels

Emulsion gel is a semi-solid or solid material with a three-dimensional net structure produced from emulsion through physical, enzymatic, chemical methods or their combination. Emulsion gels are widely used in food, pharmaceutical and cosmetic industries as carriers of bioactive substances and fat substitutes due to their unique properties. The modification of raw materials, and the application of different processing methods and associated process parameters profoundly affect the ease or difficult of gel formation, microstructure, hardness of the resulting emulsion gels. This paper reviews the important research undertaken in the last decade focusing on classification of emulsion gels, their preparation methods, the influence of processing method and associated process parameters on structure-function of emulsion gels. It also highlights current status of emulsion gels in food, pharmaceutical and medical industries and provides future outlook on research directions requiring to provide theoretical support for innovative applications of emulsion gels, particularly in food industry.

A critical review of RG-I pectin: sources, extraction methods, structure, and applications

In recent years, RG-I pectin isolated by low-temperature alkaline extraction methods has attracted the attention of a large number of researchers due to its huge health benefits. However, studies on other applications of RG-I pectin are still lacking. In this study, we summarized the sources (e.g. potato pulp, sugar beet pulp, okra, apple pomace, citrus peel, pumpkin, grapefruit, ginseng, etc.), extraction methods, fine structure and applications of RG-I pectin in physiological activities (e.g. anti-cancer, anti-inflammatory, anti-obesity, anti-oxidation, immune regulation, prebiotics, etc.), emulsions, gels, etc. These neutral sugar side chains not only endow RG-I pectin with various physiological activities but the entanglement and cross-linking of these side chains also endow RG-I pectin with excellent emulsifying and gelling properties. We believe that this review can not only provide a comprehensive reading for new workers interested in RG-I pectin, but also provide a valuable reference for future research directions of RG-I pectin.

Effects of glycation with chitooligosaccharide on digestion and fermentation processes of lactoferrin in vitro

This study aimed to investigate the digestion and fermentation processes of lactoferrin (LF) glycated with chitooligosaccharide (COS) under a controlled Maillard reaction, utilizing the in vitro digestion and fermentation model, and to compare the results of these processes to LF undertaken without glycation. After gastrointestinal digestion, the products of the LF-COS conjugate were found to have more fragments with lower molecular weight than LF, and the antioxidant capabilities (via ABTS and ORAC assay) of the LF-COS conjugate digesta also increased. In addition, the undigested fractions could be further fermented by the intestinal microbiota. Compared with LF, more short-chain fatty acids (SCFAs) were generated (from 2397.40 to 2623.10 μg/g), and more species of microbiota (from 451.78 to 568.10) were observed in LF-COS conjugate treatment. Furthermore, the relative abundance of Bacteroides and Faecalibacterium that could utilize carbohydrates and metabolic intermediates to produce SCFAs also increased in LF-COS conjugate than that of LF. Our results demonstrated that glycation with COS under the controlled wet-heat treatment Maillard reaction could modify the digestion of LF and have a potentially positive influence on the intestinal microbiota community.

High-temperature glycosylation modifies the molecular structure of ovalbumin to improve the freeze-thaw stability of its high internal phase emulsion

In this study, ovalbumins (OVAs) were glycosylated with fructo-oligosaccharide (FO) at different temperatures (80 °C, 100 °C, 120 °C, and 140 °C) and durations (1 h and 2 h) via wet-heating. The glycosylated OVAs (GOVAs) were characterized by the degree of glycosylation (DG), particle size, zeta potentials, and structural changes. GOVAs-stabilized high-internal-phase emulsions (HIPEs) were then prepared to compare their macro- and microstructure and freeze-thaw stability. The results showed that the DG of GOVAs increased with the increase in glycosylation temperature and the protein structure unfolded with it. Glycosylation decreased the particle size, zeta potential, and α-helical structures and increased the β-sheets and surface hydrophobicity (H₀) of GOVAs compared with unmodified OVAs. Moreover, GOVAs-stabilized HIPEs exhibited smaller particle sizes, zeta potentials, agglomeration indexes, oil loss rates, and freezing points and higher viscoelasticity, centrifugal stabilities, flocculation indexes, and freeze-thaw stabilities. Notably, HIPEs prepared by GOVAs (glycosylated higher than 120 °C) showed the least changes in macro- and microscopic appearances after freeze-thawing. These findings will provide a novel method for improving and broadening the functionalities of OVAs and potentially develop HIPEs with enhanced freeze-thaw stabilities.

Antioxidant Activity and Cell Protection of Glycosylated Products in Different Reducing Sugar Duck Liver Protein Systems

Duck liver is an important by-product of duck food. In this study, we investigated the effects of glucose, fructose, and xylose on the antioxidant properties of glycosylated products of duck liver protein and their protective effects on HepG2 cells. The results show that the glycosylation products of the three duck liver proteins (DLP-G, DLP-F, and DLP-X) all exhibit strong antioxidant activity; among three groups, DLP-X shows the strongest ability to scavenge DPPH, ·OH free radicals, and ABTS⁺ free radicals. The glycosylated products of duck liver protein are not toxic to HepG2 cells and significantly increase the activity of antioxidant enzymes such as SOD, CAT, and GSH-Px in HepG2 cells at the concentration of 2.0 g/L, reducing oxidative stress damage of cells (p < 0.05). DLP-X has a better effect in reducing oxidative damage and increasing cellular activity in HepG2 cells than DLP-G and DLP-F (p < 0.05). In this study, the duck liver protein glycosylated products by glucose, fructose, and xylose were named as DLP-G, DLP-F, and DLP-X, respectively.

Glycosylation with bioactive polysaccharide obtained from Rosa roxburghii Tratt fruit to enhance the oxidative stability of whey protein isolate emulsion

Whey protein isolate (WPI) is an excellent source of emulsifier, but its function is limited for oxidative unstable in emulsion. In this study, WPI was glycated with Rosa roxburghii Tratt fruit polysaccharides (RTFP) by Maillard reaction under optimum conditions. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis profile confirmed the formation of WPI-RTFP conjugates. The intrinsic fluorescence spectrum, CD and FT-IR indicated that the structure of WPI was affected after glycated with RTFP. In addition, the antioxidant activity of WPI-RTFP conjugates and WPI-RTFP emulsion were 3.5-fold and 1.5-fold stronger than that of WPI and WPI emulsion, respectively. Furthermore, the emulsion coated by conjugates demonstrated better oxidative stability than WPI with less peroxides produced after accelerated oxidation for 7 days. The results lay good foundation for the modification of protein by natural bioactive polysaccharides as well as for the application in healthy foods.