Influence of pulsed light treatment on the aggregation of whey protein isolate

Effect of thermal and non-thermal processing methods on the Structural and Functional Properties of Whey Protein from Donkey Milk

This study evaluated the impact of thermal, ultrasonication, and UV treatment on the structural and functional properties of whey proteins from donkey milk (DWP). Whey proteins exhibited notable stability in non-heat-treated environments, while their structural and functional characteristics were notably impacted by excessive heat treatment. The application of high-temperature long-time thermal treatment (HTLT) resulted in a decrease in fluorescence intensity, foaming and emulsification stability, and considerable damage to the active components of the proteins. Specifically, the preservation of lysozyme activity was only 23%, and lactoferrin and immunoglobulin G exhibited a significant loss of 70% and 77%, respectively. Non-thermal treatment methods showed superior efficacy in preserving the active components in whey proteins compared with heat treatment. Ultrasonic treatment has demonstrated a notable capability in diminishing protein particle size and turbidity, and UV treatment has been observed to have the ability to oxidize internal disulfide bonds within proteins, consequently augmenting the presence of free sulfhydryl groups, which were beneficial to foaming and emulsification stability. This study not only offers a scientific basis for the processing and application of DWP but also serves as a guide to produce dairy products, aiding in the development of dairy products tailored to specific health functions.

Nonthermal Sterilization of Animal-based Foods by Intense Pulsed Light Treatment

The consumption of meat has been increasing, leading to a dynamic meat and meat processing industry. To maintain the quality and safety of meat products, various technologies have been explored, including intense pulsed light (IPL) technology. Several factors affect the inactivation of microorganisms by IPL treatment, including light intensity (fluence), treatment duration, pulse frequency, and the distance between the lamp and the samples. Meat products have been studied for IPL treatment, resulting in microbial reductions of approximately 0.4-2.4 Log. There are also impacts on color, sensory attributes, and physico-chemical quality, depending on treatment conditions. Processed meat products like sausages and ham have shown microbial reductions of around 0.1-4 Log with IPL treatment. IPL treatment has minimal impact on color and lipid oxidation in these products. Egg products and dairy items can also benefit from IPL treatment, achieving microbial reductions of around 1-7.8 Log. The effect on product quality varies depending on the treatment conditions. IPL technology has shown promise in enhancing the safety and quality of various food products, including meat, processed meat, egg products, and dairy items. However, the research results on animal-based food are not diverse and fragmentary, this study discusses the future research direction and industrial application through a review of these researches.

Improved encapsulation effect and structural properties of whey protein isolate by dielectric barrier discharge cold plasma

The whey protein isolate (WPI) was modified by dielectric barrier discharge cold plasma (DBD) in order to improve its encapsulation efficiency of rutin. In this work, the effect of DBD treatment on structure and physicochemical properties of WPI and the interaction between DBD-treated WPI and rutin were investigated. The results showed that the structural change of WPI leaded to the exposure of internal hydrophobic groups, increasing the interaction site with rutin. The encapsulation efficiency of DBD-treated WPI (30 kV, 30 s) on rutin was improved by 12.42 % compared with control group. The results of multispectral analysis showed that static quenching occurred in the process of interaction between DBD-treated and rutin, hydrogen bond and van der Waals force were the main forces between them. Therefore, DBD treatment can be used as a method to improve the encapsulation efficiency of WPI on hydrophobic active substances.

Effects of protein aggregation induced by NaCl and temperature on gelation of silkworm (Antheraea pernyi) pupa raw powder

Edible insects have great potential for producing protein-rich ingredients. This study aimed to investigate the effects of protein aggregation induced by NaCl (0-1 M) and temperature (65-95 °C) on gelation of Antheraea pernyi (A. pernyi) pupa raw powder. No thermal aggregates were observed at low temperature (65 °C), on the basis of there being no significant enhancement in turbidity and particle size (P > 0.05), regardless of NaCl concentrations. At elevated temperatures (75-95 °C), protein solutions exhibited significantly higher turbidity and particle size (P < 0.05), accompanied by an initial rise in surface hydrophobicity followed by a decline, alongside declining sulfhydryl. This marks the beginning of massive thermal aggregation driven by molecular forces. In addition, covalent (disulfide bonds) and non-covalent (hydrogen bonding, electrostatic interactions, and hydrophobicity) forces were influenced by NaCl, leading to variability in the protein aggregation and gelation. Correlation analysis indicates that the higher protein aggregation induced by ions was beneficial to the construction of more compact three-dimensional structures, as well as to the rheology, texture, and water-holding capacity of A. pernyi pupa gels. However, excessive salt ions destroyed the gel structure. Our findings will aid the use of A. pernyi pupae as textural ingredients in formula foods.

Effect of Low-Dose Line-Spectrum and Full-Spectrum UV on Major Humoral Components of Human Blood

Ultraviolet blood irradiation (UVBI) is an alternative approach to the treatment of infectious diseases of various pathogeneses. Recently, UVBI has attracted particular interest as a new immunomodulatory method. Experimental studies available in the literature demonstrate the absence of precise mechanisms of the effect of ultraviolet radiation (UV) on blood. Here, we investigated the effect of UV radiation of line-spectrum mercury lamp (doses up to 500 mJ/cm²) traditionally used in UVBI on the major humoral blood components: albumin, globulins and uric acid. Preliminary data on the effect of various doses of UV radiation of full-spectrum flash xenon lamp (doses up to 136 mJ/cm²), a new promising source for UVBI, on the major blood plasma protein, albumin, are presented. The research methodology included spectrofluorimetric analysis of the oxidative modification of proteins and analysis of the antioxidant activity of humoral blood components by chemiluminometry. The effect of UV radiation on albumin caused its oxidative modification and, accordingly, an impairment of the transport properties of the protein. At the same time, UV-modified albumin and γ-globulins acquired pronounced antioxidant properties compared to native samples. Uric acid mixed with albumin did not protect the protein against UV-induced oxidation. The flash full-spectrum UV qualitatively had the same effect on albumin as line-spectrum UV did, but an order of magnitude lower doses were required to achieve comparable effects. The suggested protocol can be used for selecting a safe individual dose for UV therapy.

Impact of Cavitation Jet on the Structural, Emulsifying Features and Interfacial Features of Soluble Soybean Protein Oxidized Aggregates

A cavitation jet can enhance food proteins' functionalities by regulating solvable oxidized soybean protein accumulates (SOSPI). We investigated the impacts of cavitation jet treatment on the emulsifying, structural and interfacial features of soluble soybean protein oxidation accumulate. Findings have shown that radicals in an oxidative environment not only induce proteins to form insoluble oxidative aggregates with a large particle size and high molecular weight, but also attack the protein side chains to form soluble small molecular weight protein aggregates. Emulsion prepared by SOSPI shows worse interface properties than OSPI. A cavitation jet at a short treating time (<6 min) has been shown to break the core aggregation skeleton of soybean protein insoluble aggregates, and insoluble aggregates into soluble aggregates resulting in an increase of emulsion activity (EAI) and constancy (ESI), and a decrease of interfacial tension from 25.15 to 20.19 mN/m. However, a cavitation jet at a long treating time (>6 min) would cause soluble oxidized aggregates to reaggregate through an anti-parallel intermolecular β-sheet, which resulted in lower EAI and ESI, and a higher interfacial tension (22.44 mN/m). The results showed that suitable cavitation jet treatment could adjust the structural and functional features of SOSPI by targeted regulated transformation between the soluble and insoluble components.

Plant Protein versus Dairy Proteins: A pH-Dependency Investigation on Their Structure and Functional Properties

Plant proteins are constantly gaining attention as potential substitutes for dairy proteins, due to their suitable functionality and nutritional value. This study was designed to compare the structural and functional responses of different plant protein isolates (soy, pea, lentil, and chickpea) with two commonly used dairy protein (whey protein isolates and sodium caseinate) under different pH treatments (pH 3.0, 5.0, 7.0, and 9.0). The results showed that pH had a different alteration on the structural, surface properties and functional properties of plant and dairy proteins. Plant protein generally possessed a darker color, lower solubility, emulsifying properties, and foaming capacity, whereas their foaming stability and water holding capacity were higher than those of dairy proteins. Soy protein isolates were characterized by its comparable proportion of β-turn and random coils, zeta-potential, emulsifying (30.37 m²/g), and water-holding capacity (9.03 g/g) at alkaline conditions and chickpea protein isolates showed good oil-holding capacity (3.33 g/g at pH 9) among plant proteins. Further analysis confirmed that pH had a greater influence on the structural and functional properties of proteins as compared to protein sources, particularly at acidic conditions. Overall, this study might help processors select the appropriate plant protein as dairy alternatives for their target application in plant-based food products.

Crystallization of Lactose-Protein Solutions in the Presence of Flavonoids

Lactose is commonly crystallized in the presence of whey proteins, forming co-crystals of lactose and proteins. This work hypothesized that flavonoids such as rutin or epigallocatechin-3-gallate (EGCG) could be incorporated into the lactose and protein co-crystal structure since flavonoids may interact with both lactose and proteins. The interactions between whey proteins and flavonoids were first studied. Then, lactose-protein solutions were crystallized with and without flavonoids, measuring the kinetic parameters of crystallization and characterizing the resulting crystals. The incorporation of flavonoids in lactose-protein co-crystals depended on the hydrophilic nature of flavonoids. The hydrophilic EGCG was scarcely enclosed in the crystal lattice of lactose and avoided the inclusion of whey proteins in the crystals. In contrast, the less water-soluble rutin interacted with whey proteins and lactose, leading to the formation of co-crystals containing lactose, protein, and a large concentration of rutin (3.468 ± 0.392 mg per 100 mg of crystals).

Physicochemical, structural and adhesion properties of walnut protein isolate-xanthan gum composite adhesives using walnut protein modified by ethanol

Low-sugar and high-protein adhesives have broad market application prospects, while natural plant proteins have confronted technical bottlenecks due to their poor adhesion. In this study, the effects of ethanol with different concentrations (0-80%) on the adhesion properties of walnut protein isolate-xanthan gum (WNPI-XG) composite adhesives were investigated. Results showed the bonding strength of WNPI-XG treated with 40% ethanol reached 12.55 MPa, the denaturation temperature and the surface hydrophobicity increased to 87.91 and 185.07 respectively, displaying the best rheological and texture properties. It also indicated appropriate concentration of ethanol (40%) didn't change the molecular weight of WNPI-XG, but greatly strengthened the fluorescence intensity, leading changes in contents of reactive sulfhydryl groups, electrostatic forces, hydrophobic interactions, hydrogen bonds and disulfide bonds. Furthermore, the treatment also facilitated a conformation conversion of the secondary structures from β-sheet to α-helix, promoting the full unfolding of protein molecules. The microstructure analysis showed after 40% ethanol treatment, the WNPI structure was uniform, the surface of WNPI-XG adhesive was flat and smooth, combined more closely with water molecules. By analyzing the influence of ethanol treatment on adhesion of WNPI-XG, the research laid a theoretical foundation for protein modification, providing good technical references for its development and utilization.

Comparative Study of Oxidative Structural Modifications of Unadsorbed and Adsorbed Proteins in Whey Protein Isolate-Stabilized Oil-in-Water Emulsions under the Stress of Primary and Secondary Lipid Oxidation Products

The impact of typical primary or secondary lipid oxidation (LPO) products, selected as linoleic acid 13-hydroperoxide (13-HPODE) and malondialdehyde (MDA), on the structural modification of unadsorbed or adsorbed proteins in whey protein isolate (WPI)-stabilized oil-in-water (O/W) emulsions during storage up to 48 h at 37 °C in the dark was investigated. The results showed that either 13-HPODE and MDA could lead to structural modifications of unadsorbed or adsorbed proteins with a concentration-dependent manner and time relationship, respectively. Moreover, higher levels of MDA rendered a higher degree of oxidative modifications of WPI than 13-HPODE, indicated by the higher protein carbonyl contents and N'-formyl-L-kynurenine (NFK) and lower fluorescence intensity. Additionally, adsorbed proteins were more easily oxidized by LPO products than unadsorbed proteins. Overall, our results indicated that the formation of secondary LPO products and the protein position were crucial factors to increase the degree of oxidative modifications of WPI in O/W emulsion systems.

Effect of reaction temperature on the protein structure and the ability to encapsulate β-carotene of WPI-dextran conjugates

In this paper, we studied the effect of glycosylation reaction on the molecular structure and functional properties of whey protein isolate (WPI), and studied the effect of reaction temperature (50 to 90 °C) on the molecular structure and functional properties of WPI-dextran conjugates (WPI-D). The results of the extent of glycation (EG) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis confirmed the formation of WPI-D. Circular dichroism (CD), Fourier transform infrared spectrum, and fluorescence spectroscopy indicated that the molecular structure of WPI was changed after glycosylation-the β-sheet content was decreased and the tryptophan content was increased. The emulsifying properties and the ability to encapsulate β-carotene of WPI-D were improved compared with WPI (P < 0.05). When the reaction temperature was 70 and 80 °C, the EG and the ability to encapsulate β-carotene of WPI-D were better (P < 0.05), which was related to protein unfolding. However, due to the polymerization between the WPI molecules, the emulsion activity index of WPI-D and the ability to encapsulate β-carotene were lowered at 90 °C (P < 0.05). Therefore, the glycosylation reaction can change the molecular structure and functional properties of WPI; the emulsifying properties and the ability to encapsulate β-carotene of WPI-D can be changed by controlling the reaction temperature of glycosylation. PRACTICAL APPLICATION: The glycosylation reaction can change the molecular structure and functional properties of Whey protein isolate; the emulsifying properties and the ability to encapsulate β-carotene of WPI-dextran conjugates can be changed by controlling the reaction temperature of glycosylation.