The influence of glycosylation on the antigenicity, allergenicity, and structural properties of 11S-lactose conjugates

Dietary glycation compounds - implications for human health

The term "glycation compounds" comprises a wide range of structurally diverse compounds that are formed endogenously and in food via the Maillard reaction, a chemical reaction between reducing sugars and amino acids. Glycation compounds produced endogenously are considered to contribute to a range of diseases. This has led to the hypothesis that glycation compounds present in food may also cause adverse effects and thus pose a nutritional risk to human health. In this work, the Senate Commission on Food Safety (SKLM) of the German Research Foundation (DFG) summarized data on formation, occurrence, exposure and toxicity of glycation compounds (Part A) and systematically assessed potential associations between dietary intake of defined glycation compounds and disease, including allergy, diabetes, cardiovascular and renal disease, gut/gastrotoxicity, brain/cognitive impairment and cancer (Part B). A systematic search in Pubmed (Medline), Scopus and Web of Science using a combination of keywords defining individual glycation compounds and relevant disease patterns linked to the subject area of food, nutrition and diet retrieved 253 original publications relevant to the research question. Of these, only 192 were found to comply with previously defined quality criteria and were thus considered suitable to assess potential health risks of dietary glycation compounds. For each adverse health effect considered in this assessment, however, only limited numbers of human, animal and in vitro studies were identified. While studies in humans were often limited due to small cohort size, short study duration, and confounders, experimental studies in animals that allow for controlled exposure to individual glycation compounds provided some evidence for impaired glucose tolerance, insulin resistance, cardiovascular effects and renal injury in response to oral exposure to dicarbonyl compounds, albeit at dose levels by far exceeding estimated human exposures. The overall database was generally inconsistent or inconclusive. Based on this systematic review, the SKLM concludes that there is at present no convincing evidence for a causal association between dietary intake of glycation compounds and adverse health effects.

Film-forming properties and mechanisms of soy protein: Insights from β-conglycinin and glycinin

Extensive research has been conducted on soy protein films; however, limited information is available regarding the influence of the major components, β-conglycinin (7S) and glycinin (11S), on the film-forming properties of soy protein. This study aimed to isolate the 7S and 11S fractions in order to prepare films and investigate the impact of varying 7S/11S ratios on the film-forming solutions (FFS) and film properties. The findings revealed that higher 11S ratios led to increased protein aggregation, consequently elevating the storage modulus (G') of the FFS. Notably, an optimal 7S/11S ratio of 7S1:11S2 (CF3) significantly enhanced the film's water resistance. Specifically, it enhanced the water contact angle by an impressive 17.44 % and reduced the water vapor transmission rate by 27.56 %. These improvements were attributed to intermolecular interactions, involving hydrogen bonds and salt bridges, between the amino acid residues of 7S and 11S. As a result, a more uniform and dense microstructure was achieved. Interestingly, the mechanical and optical properties of the film were maintained by the different protein fractions examined. In summary, this study contributes to the understanding of the film-forming properties of soy protein, particularly the role of 7S and 11S.

A comprehensive review on glycation and its potential application to reduce food allergenicity

Food allergens are a major concern for individuals who are susceptible to food allergies and may experience various health issues due to allergens in their food. Most allergenic foods are subjected to heat treatment before being consumed. However, thermal processing and prolonged storage can cause glycation reactions to occur in food. The glycation reaction is a common processing method requiring no special chemicals or equipment. It may affect the allergenicity of proteins by altering the structure of the epitope, revealing hidden epitopes, concealing linear epitopes, or creating new ones. Changes in food allergenicity following glycation processing depend on several factors, including the allergen's characteristics, processing parameters, and matrix, and are therefore hard to predict. This review examines how glycation reactions affect the allergenicity of different allergen groups in allergenic foods.

Recent advances in soybean protein processing technologies: A review of preparation, alterations in the conformational and functional properties

Currently, growing concerns about sustainable development and health awareness have driven the development of plant-based meat substitutes. Soybean proteins (SPs) are eco-friendly and high-quality food sources with well-balanced amino acids to meet consumer demand. The functionality and physicochemical attributes of SPs can be improved by appropriate processing and modification. With the burgeoning advances of modern processing technologies in the food industry, a multitude of functional foods and ingredients can be manufactured based on SPs. This review mainly highlights the conformational changes of SPs under traditional and emerging processing technologies and the resultant functionality modifications. By elucidating the relationship between processing-induced structural and functional alterations, detailed and systematic insights are provided regarding the exploitation of these techniques to develop different nutritional and functional soybean products. Some popular methods to modify SPs properties are discussed in this paper, including thermal treatment, fermentation, enzyme catalysis, high hydrostatic pressure, high-intensity ultrasound, atmospheric cold plasma, high-moisture extrusion, glycosylation, pulsed ultraviolet light and interaction with polyphenols. Given these processing technologies, it is promising to expand the application market for SPs and boost the advancement of the soybean industry.

Molecular structure and functional properties of glycinin conjugated to κ-carrageenan and guar gum: A comparative study

Molecular structure and functional properties of glycinin conjugated to κ-carrageenan and guar gum using a dry-heating method were comparatively analyzed. Glycosylation was confirmed by analyzing the degree of grafting, protein subunit composition, infrared absorption profile, and changes in contents of protein secondary structures. K-carrageenan was proven to possess a greater susceptibility to be grafted to glycinin than guar gum due to its relatively low molecular weight and negatively charged characteristics. The improvement of solubility by glycosylation with guar gum near the isoelectric point of glycinin was better than that by glycosylation with κ-carrageenan. Glycinin glycosylated with both polysaccharides exhibited enhanced emulsifying activity and stability. The enhanced apparent viscosity, elastic modulus, and viscous modulus also demonstrated that glycosylation promoted the appearance of stable elastic network structure. In summary, glycosylation with these two polysaccharides conferred glycinin superior emulsifying and rheological properties, and κ-carrageenan exhibited a better performance compared to guar gum.

Maillard Reaction Induced Changes in Allergenicity of Food

Food allergy is increasing in prevalence, posing aheavier social and financial burden. At present, there is still no widely accepted treatment for it. Methods to reduce or eliminate the allergenicity of trigger foods are urgently needed. Technological processing contributes to producing some hypoallergenic foods. Among the processing methods, the Maillard reaction (MR) is popular because neither special chemical materials nor sophisticated equipment is needed. MR may affect the allergenicity of proteins by disrupting the conformational epitope, disclosing the hidden epitope, masking the linear epitope, and/or forming a new epitope. Changes in the allergenicity of foods after processing are affected by various factors, such as the characteristics of the allergen, the processing parameters, and the processing matrix, and they are therefore variable and difficult to predict. This paper reviews the effects of MR on the allergenicity of each allergen group from common allergenic foods.

Soybean allergy: characteristics, mechanisms, detection and its reduction through novel food processing techniques

Human beings have consumed soybean as an excellent food source for thousand years due to its rich protein, fatty acids, minerals, and fibers. However, soybeans were recognized as one of the big eight allergens resulting in allergic symptoms and even could lead to death. With the increasing demand for soybean products, the challenges caused by soybean allergy need to be solved urgently. This review detailly described the pathogenesis and clinical characteristics of soybean allergy, and also the advantages and disadvantages of four different diagnostic methods were summarized. The major soybean allergens and their structures were summarized. Three types of soybean allergy including Type I, III, and IV, which could trigger allergic reactions were reported in this review. Summary in four different diagnostic methods showed that double-blind, placebo-controlled food challenge is recognized as a gold standard for diagnosing soybean allergy. Three types of processing techniques in reducing soybean allergy were discussed, and the results concluded that some novel food processing techniques such as ultrasound, cold-plasma treatment, showed potential application in the reduction of soybean allergenicity. Further, some suggestions regarding the management and treatment of food allergies were addressed in this review.

Covalent and non-covalent interactions of cyanidin-3-O-glucoside with milk proteins revealed modifications in protein conformational structures, digestibility, and allergenic characteristics

Currently, there is a need to explore the effects of different types of protein-anthocyanin complexations, as well as the possible changes in the nutrition and allergenicity of the formed complexes. Here, we systematically investigated the covalent and non-covalent interactions between cyanidin-3-O-glucoside (C3G) and two major milk proteins, α-casein (α-CN) and β-lactoglobulin (β-LG). Fluorescence quenching data showed that, under non-covalent conditions, C3G quenched the fluorescence of the two proteins via a static process, with the interaction forces being revealed; for covalent products, decreased fluorescence intensities were observed with red shifts in the λ_max. Multiple spectroscopic analyses implied that C3G-addition induced protein structural unfolding through transitions between the random coil and ordered secondary components. With a two-stage simulated gastrointestinal (GI) digestion model, it was seen that covalent complexes, not their non-covalent counterparts, showed reduced protein digestibility, ascribed to structural changes resulting in the unavailability of enzyme cleaving sites. The GI digests displayed prominent 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation-scavenging abilities (3.8-11.1 mM Trolox equivalents per mL digest), in contrast to the markedly reduced 1,1-diphenyl-2-picrylhydrazyl radical-scavenging capacities. Additionally, covalent protein-C3G complexes, but not their non-covalent counterparts, showed lower IgE-binding levels in comparison to the native control. This study provides new understanding for the development of anthocyanin-milk protein systems as functional ingredients with health-beneficial properties.

Eucommia ulmoides Leaf Polysaccharide in Conjugation with Ovalbumin Act as Delivery System Can Improve Immune Response

In this investigation, to maximize the desired immunoenhancement effects of PsEUL and stimulate an efficient humoral and cellular immune response against an antigen, PsEUL and the model antigen ovalbumin (OVA) were coupled using the N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC) reaction to yield a novel delivery system (PsEUL-OVA). The physicochemical characteristics and immune regulation effects of this new system were investigated. We found the yield of this EDC method to be 46.25%. In vitro, PsEUL-OVA (200 μg mL⁻¹) could enhance macrophage proliferation and increase their phagocytic efficiency. In vivo, PsEUL-OVA could significantly increase the levels of OVA-specific antibody (IgG, IgG1, IgG2a, and IgG2b) titers and cytokine (IL-2, IL-4, IL-6, IFN-γ) levels. Additionally, it could activate T lymphocytes and facilitate the maturation of dendritic cells (DCs). These findings collectively suggested that PsEUL-OVA induced humoral and cellular immune responses by promoting the phagocytic activity of macrophages and DCs. Taken together, these results revealed that PsEUL-OVA had the potential to improve immune responses and provide a promising theoretical basis for the design of a novel delivery system.

Effects of heat treatment on the antigenicity, antigen epitopes, and structural properties of β-conglycinin

In this study, the effects of heat treatment on antigenicity, antigen epitopes, and structural changes in β-conglycinin were investigated. Results showed that the IgG (Immunoglobulin G) binding capacity of heated protein was inhibited with increased temperature, although IgE (Immunoglobulin E) binding capacity increased. Linear antigen epitopes generally remained intact during heat treatment. After heat treatment, β-conglycinin was more easily hydrolyzed by digestive enzymes, and a large number of linear epitopes was destroyed. In addition, heat denaturation of β-conglycinin led to the formation of protein aggregates and reduction of disulfide bonds. The contents of random coils and β-sheet of heated β-conglycinin decreased, but the contents of β-turn and α-helix increased. Moreover, the protein structure of heated β-conglycinin unfolded, more hydrophobic regions were exposed, and the tertiary structure of β-conglycinin was destroyed. Heat treatment affected the antigenicity and potential sensitization of β-conglycinin by changing its structure.

Identification of the linear immunodominant epitopes in the β subunit of β-conglycinin and preparation of epitope antibodies

β-conglycinin is one of the major allergens in soybean protein. The purpose of this study was to predict and to identify the major linear epitopes of the β subunit of β-conglycinin. Potential linear epitopes were predicted and confirmed by three immunoinformatics tools combined with the Immune Epitope Database (IEDB). Ten potential epitope peptides were synthesized by Fmoc (9-fluorenylmethoxycarbonyl) solid phase peptide synthesis and were validated by the indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) using sera from soybean allergic patients. Polyclonal antibodies, which were prepared by immunizing rabbits with synthesized peptides, were used to confirm their binding ability with β-conglycinin through western blot and dot blot assays. The results showed that 10 peptides were screened as the main epitopes for the β subunit of β-conglycinin. All 10 peptides (P1-P10) presented IgG binding activity, and P2 and P6 were also validated as IgE binding peptides. Moreover, the results of dot blot showed that P5 and P8 might be located inside the protein molecule. Western blot indicated that most of polyclonal antibodies were bound effectively to the β subunit of β-conglycinin. In addition, few polyclonal antibodies exhibited an immune cross-reaction with the α and α' subunits.

Effect of Fructus Mori. bioactive polysaccharide conjugation on improving functional and antioxidant activity of whey protein

Whey protein with high biological and technological values is an excellent source of nutrition. However, the limited functional properties prevent its widespread applications in food industry. In this study, the whey protein functionality was improved via glycation with mulberry fruit polysaccharide by Maillard reaction. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis profile and free amino groups determination confirmed the glycation occurred between whey protein and mulberry fruit polysaccharide. The emulsion capacity and stability of the conjugates were 1.40-fold and 1.52-fold higher than that of whey protein. The conjugates also exhibited remarkably improved antioxidant activity. The fish oil emulsion coated by conjugates demonstrated smaller droplet size, better storage and oxidative stability than that stabilized by whey protein. The findings would be of vital importance for updated understanding of the modification in emulsifying properties of proteins by glycation with natural bioactive polysaccharides as well as for the development of healthy foods.

The separation and identification of the residual antigenic fragments in soy protein hydrolysates

Soybean is one of the major food allergens. In this study, soy protein isolate was hydrolyzed by Neutrase and Flavourzyme. The hydrolysates were separated by ultrafiltration and ion-exchange chromatography. The antigenicity of proteins was determined by indirect competitive ELISA. The molecular weight distribution was characterized by SDS-PAGE. The amino acid sequence of chromatography fractions was analyzed by LC-MS. The results showed that proteins with >50 kDa in hydrolysates had the highest antigenicity and were further separated into F1 -F5 fragments by ion-exchange chromatography. Fragment F4 , which was the most antigenic, was analyzed by LC-MS. The results of mass spectrometry showed that most of the peptides that contained antigen epitopes in chromatography fraction F4 belonged to glycinin subunits. The antigenicity of soy protein was reduced by enzymatic hydrolysis, but glycinin showed resistance to enzymatic hydrolysis. PRACTICAL APPLICATIONS: The identification of residual antigenicity in soy protein hydrolysates by LC-MS provides important information on the resistance mechanism of enzymatic hydrolysis of soybean protein allergens. In addition, the efficient separation of soy protein hydrolysates could be beneficial for developing low-allergenic soybean products.

Effects of irradiation on the structure and properties of glycosylated soybean proteins

At present, there are few reports on the glycosylation modification of soybean proteins under irradiation. In this paper, a soybean protein isolate and maltose were used as raw materials to prepare a glycosylated soybean protein under gamma-ray treatment to improve the functional properties and evaluate the changes in the structure. The results of analysis of the graft degree, browning index, polyacrylamide gel electrophoresis, infrared spectrum, fluorescence spectrum and ultraviolet spectrum of the modified product showed that the Maillard reaction between the soybean protein isolate and maltose occurred and the structure of the reaction product changed. When the irradiation dose was 7.5 kGy, the solubility of modified products increased by 23 ± 0.21% compared with that of the control group. The foaming property and foam stability increased by 62.5 ± 0.34% and 41 ± 0.47%, respectively. Emulsification, water absorption capacity and fat absorption capacity of glycosylated compounds also increased significantly. Compared with other modification methods, irradiation technology had the advantages of short action time, high efficiency and low cost, and more importantly, its industrial production was easy to implement. This experiment combined irradiation technology with the glycosylation modification method. It was proved that irradiation could promote the Maillard reaction between the soybean protein isolate and maltose, and significantly improve the functional properties of the modified protein, providing theoretical and technical support for expanding the application of the soy protein isolate in the food industry.

Molecular Mechanism for Improving Emulsification Efficiency of Soy Glycinin by Glycation with Soy Soluble Polysaccharide

Glycation with carbohydrates has been considered to be an effective strategy to improve the emulsifying properties of plant storage globulins, but the knowledge is inconsistent and even contradictory. This work reported that the glycation with soy soluble polysaccharide (SSPS) progressively improved the emulsification efficiency of soy glycinin (SG) in a degree-of-glycation (DG)-dependent manner. The glycation occurred in both the acidic (A) and basic (B) polypeptides to a similar extent. The physicochemical and structural properties of glycated SG samples with different DG values of 0-35% were characterized. The emulsifying properties of unglycated and glycated SG were performed on the emulsions at an oil fraction of 0.3 and a protein concentration in the aqueous phase, produced using microfluidization as the emusification process. The glycation with increasing the DG led to a progressive decrease in solubility and surface hydrophobicity but remarkably increased the magnitude of ζ-potential. Dynamic latter scattering and spectroscopic results showed that the glycation resulted in a gradual dissociation of the 11S-form SG at the quaternary level (into different [AB] subunits), in a DG-dependent way, while their tertiary ([AB] subunits) and secondary structure were slightly affected. Besides the emulsification efficiency, the glycation progressively accelerated the droplet flocculation and facilitated the adsorption of the proteins at the interface and formation of bridged emulsions. The results demonstrated that the improvement of the emulsification efficiency of SG by the glycation with SSPS was largely attributed to the enhanced conformation flexibility at the [AB] subunit level as well as facilitated formation of bridged emulsions. It was also confirmed that once the glycated SG adsorbed at the interface, it would readily dissociated into subunits; the dissociated [AB] subunits exhibited an outstanding Pickering stabilization. The findings would be of importance for providing new knowledge about the molecular mechanism for the modification of emulsifying properties of oligomeric globulins by the glycation with polysaccharides.