Studying the effects of high pressure-temperature treatment on the structure and immunoreactivity of β-lactoglobulin using experimental and computational methods

Changes of structure properties and potential allergenicity of ovalbumin under high hydrostatic pressures

Egg proteins, notably ovalbumin (OVA), contribute to a prevalent form of food allergy, particularly in children. This study aims to investigate the impact of high hydrostatic pressure (HHP) treatment at varying levels (300, 400, 500, and 600 MPa) on the molecular structure and allergenicity of OVA. The structure of HHP-treated OVA was assessed through fluorescence spectroscopy, circular dichroism spectroscopy, and molecular dynamics (MD) simulation. HHP treatment (600 MPa) altered OVA structures, such as α-helix content decreased from 28.07 % to 19.47 %, and exogenous fluorescence intensity increased by 8.8 times compared to that of the native OVA. The free sulfhydryl groups and zeta potential value were also increased with HHP treatment (600 MPa). ELISA analysis and MD simulation unveiled a noteworthy reduction in the allergenicity of OVA when subjected to 600 MPa for 10 min. Overall, this study suggests that the conformational changes in HHP-treated OVA contribute to its altered allergenicity.

Effects of high pressure processing on structural changes, aggregation, and binding mechanisms of β-Lactoglobulin with typical polyphenols

The binding capacity of β-Lactoglobulin (BLG) is crucial for delivering polyphenols, influenced by structural changes. High pressure processing (HPP) has the potential to modify BLG's structure and aggregation, but its specific impact on BLG-polyphenol interactions is uncertain. This study used circular dichroism spectroscopy and molecular dynamics simulations to reveal HPP-induced structural changes in BLG, supported by particle size analysis indicating aggregation. Seven structurally diverse polyphenols (quercetin-QR, hesperetin-HSP, dihydromyricetin-DHM, gallic acid-GA, (-)-epicatechin-EC, resveratrol-RES, and secoisolariciresinol diglucoside-SDG) were investigated to comprehensively analyze their binding patterns using fluorescence spectroscopy and molecular docking. HPP reduced BLG's ordered structure and increased its aggregation. Binding affinities peaked at 400 MPa for DHM, QR, HSP, GA, and RES, while SDG and EC exhibited maximum affinities at atmospheric pressure and 600 MPa, respectively. Elevated pressures enhanced BLG-polyphenol interactions, particularly at residues 44GLU and 160CYS, with van der Waals forces dominating the binding free energy.

The mechanism of epigallocatechin-3-gallate inhibiting the antigenicity of β-lactoglobulin under pH 6.2, 7.4 and 8.2: Multi-spectroscopy and molecular simulation methods

The antigenicity of β-lactoglobulin (β-LG) can be influenced by pH values and reduced by epigallocatechin-3-gallate (EGCG). However, a detailed mechanism concerning EGCG decreasing the antigenicity of β-LG at different pH levels lacks clarity. Here, we explore the inhibition mechanism of EGCG on the antigenicity of β-LG at pH 6.2, 7.4 and 8.2 using enzyme-linked immunosorbent assay, multi-spectroscopy, mass spectrometry and molecular simulations. The results of Fourier transform infrared spectroscopy (FTIR) and circular dichroism (CD) elucidate that the noncovalent binding of EGCG with β-LG induces variations in the secondary structure and conformations of β-LG. Moreover, EGCG inhibits the antigenicity of β-LG the most at pH 7.4 (98.30 %), followed by pH 6.2 (73.18 %) and pH 8.2 (36.24 %). The inhibitory difference is attributed to the disparity in the number of epitopes involved in the interacting regions of EGCG and β-LG. Our findings suggest that manipulating pH conditions may enhance the effectiveness of antigenic inhibitors, with the potential for further application in the food industry.

Study on potential antigenicity and functional properties of whey protein treated by high hydrostatic pressure based on structural analysis

High hydrostatic pressure (HHP) is extensively utilized in the field of food processing due to its remarkable ability to preserve the freshness of food. The potential antigenicity of β-lactoglobulin (β-LG) in whey protein isolate (WPI, 3%) treated by HHP was detected by enzyme linked immunosorbent assay (ELISA) using monoclonal antibodies. Furthermore, the impact of pressure-induced structural alterations on the emulsification properties and antioxidant activity of WPI was investigated. The findings revealed that pressures exceeding 300 MPa resulted in molecular aggregation, the formation of inter-molecular disulfide bonds, and an increase in surface hydrophobicity (H0). The percentage of β-sheet decreased along with the pressure. The results showed the increment of α-helix and β-turn with pressure. ELISA demonstrated a significant reduction in the antigenicity of β-LG following HHP treatment (100-600 MPa), with a slight recovery observed at 300 MPa. These spatial structural modifications led to the unfolding of the β-LG molecule, thereby enhancing its digestibility. Moreover, HHP treatment substantially improved the antioxidant properties, with the exposure to hydrophobic amino acids contributing to increased antioxidant properties and emulsion stability.

Insight into covalent conjugates of β-lactoglobulin with rutin: Characterizing allergenicity, digestibility, and antioxidant properties in vitro

β-lactoglobulin (β-LG) is an essential nutrient in milk, but it is the primary allergen causing dairy allergy in humans. Currently, researchers are focusing on using flavonoids to covalently modify β-LG for improving its functionality. However, the impact and underlying mechanisms of rutin covalent modification on the functional properties and allergenicity of β-LG remain unclear. Here, we aim to investigate the changes in allergenicity, digestive characteristics, and antioxidant properties of β-LG after covalent modification using a combination of spectroscopy, enzyme-linked immunosorbent assay (ELISA), simulated digestion, and antioxidant assays. The results indicate that rutin forms covalent bonds with the free amino group, sulfhydryl group, and tryptophan of β-LG, leading to alterations in the secondary structure of β-LG. Furthermore, the modified β-LG exhibits improved antioxidant capacity and decreased allergenicity, along with reduced resistance to pancreatin digestion in vitro. This study provides novel insights and strategies to expand the functional application of β-LG.

Prior interaction of protein and lipid affects the formation of ternary complexes with starch

The effects of prior interaction between β-lactoglobulin (βLG) and lauric acid (LA) on their formation of ternary complexes with wheat starch (WS) was studied. Firstly, the interaction between βLG and LA after they were heated at different temperatures between 55 and 95 °C was characterized by fluorescence spectroscopy and molecular dynamics simulation. This showed that a greater degree of βLG-LA interaction occurred after heating at higher temperatures. The WS-LA-βLG complexes formed subsequently were analyzed by differential scanning calorimetry, X-ray diffraction, Raman and FTIR spectroscopy, which showed that as interaction of βLG and LA increased there was an inhibitory action on the formation of ternary complex with WS. Hence, we conclude that there is competition in the ternary systems between the protein and starch to interact with the lipid, and that stronger interaction of the protein and lipid may hinder the formation of ternary complexes with starch.

Dissecting the essential role of N-glycosylation in catalytic performance of xanthan lyase

Modified xanthan produced by xanthan lyase has broad application prospects in the food industry. However, the catalytic performance of xanthan lyase still needs to be improved through rational design. To address this problem, in this work, the glycosylation and its influences on the catalytic performance of a xanthan lyase (EcXly), which was heterologously expressed in Escherichia coli, were reported. Liquid chromatography coupled to tandem mass spectrometry analysis revealed that the N599 site of EcXly was modified by a single N-glycan chain. Based on sequence alignment and three-dimensional structure prediction, it could be deduced that the N599 site was located in the catalytic domain of EcXly and in close proximity to the catalytic residues. After site-directed mutagenesis of N599 with alanine, aspartic acid and glycine, respectively, the EcXly and its mutants were characterized and compared. The results demonstrated that elimination of the N-glycosylation had diminished the specific activity, pH stability, and substrate affinity of EcXly. Fluorescence spectra further revealed that the glycosylation could significantly affect the overall tertiary structure of EcXly. Therefore, in prokaryotic hosts, the N-glycosylation could influence the catalytic performance of the enzyme by changing its structure. To the best of our knowledge, this is the first report about the post-translational modification of xanthan lyase in prokaryotes. Overall, our work enriched research on the role of glycan chains in the functional performance of proteins expressed in prokaryotes and should be valuable for the rational design of xanthan lyase to produce modified xanthan for industrial application.

Alteration of the allergenicity of cow's milk proteins using different food processing modifications

Milk is an essential source of protein for infants and young children. At the same time, cow's milk is also one of the most common allergenic foods causing food allergies in children. Recently, cow's milk allergy (CMA) has become a common public health issue worldwide. Modern food processing technologies have been developed to reduce the allergenicity of milk proteins and improve the quality of life of patients with CMA. In this review, we summarize the main allergens in cow's milk, and introduce the recent findings on CMA responses. Moreover, the reduced effects and underlying mechanisms of different food processing techniques (such as heating, high pressure, γ-ray irradiation, ultrasound irradiation, hydrolysis, glycosylation, etc.) on the allergenicity of cow's milk proteins, and the application of processed cow's milk in clinical studies, are discussed. In addition, we describe the changes of nutritional value in cow's milk treated by different food processing technologies. This review provides an in-depth understanding of the allergenicity reduction of cow's milk proteins by various food processing techniques.

Non-thermal Processing Technologies for Dairy Products: Their Effect on Safety and Quality Characteristics

Thermal treatment has always been the processing method of choice for food treatment in order to make it safe for consumption and to extend its shelf life. Over the past years non-thermal processing technologies are gaining momentum and they have been utilized especially as technological advancements have made upscaling and continuous treatment possible. Additionally, non-thermal treatments are usually environmentally friendly and energy-efficient, hence sustainable. On the other hand, challenges exist; initial cost of some non-thermal processes is high, the microbial inactivation needs to be continuously assessed and verified, application to both to solid and liquid foods is not always available, some organoleptic characteristics might be affected. The combination of thermal and non-thermal processing methods that will produce safe foods with minimal effect on nutrients and quality characteristics, while improving the environmental/energy fingerprint might be more plausible.