Chitooligosaccharides suppress the freeze-denaturation of actomyosin in Aristichthys nobilis surimi protein

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.

Study on the interactions between the screened polyphenols and Penaeus vannamei myosin after freezing treatment

The denaturation of proteins (particularly myosin) due to freezing can lead to the deterioration of Penaeus vannamei. The purpose of this study was to verify the antifreeze protective effects of polyphenols screened by a molecular docking technique, and to explore their interactions with myosin after freezing treatment. It was found that the screened polyphenols could significantly increase the freezing rate and unfreezable water content of shrimp paste. The results of fluorescence spectra indicated that the hesperetin to myosin quenching process included both dynamic and static quenching, and it was primarily bound to myosin through hydrophobic interactions; The quenching of myosin by both dihydroquercetin and mangiferin was static quenching, and they were bound to myosin mainly by hydrogen bonds and van der Waals forces; All three of these polyphenols had only one binding site on myosin. Surface hydrophobicity indicated that all four polyphenols were engaged in non-covalent binding (hydrophobic interactions) with myosin. Infrared spectra demonstrated that the addition of these four polyphenols significantly increased the α-helix content of myosin. They also reduced the myosin particle size, zeta potential, and protein degeneration degree. Scanning electron microscopy revealed that the four polyphenols reduced the degree of aggregation, while more uniformly distributing the myosin particles. These observations provide a basis for the screening of polyphenols and further research into the protective mechanism of polyphenols on frozen myosin.

Effect of combined treatment of L-arginine and transglutaminase on the gelation behavior of freeze-damaged myofibrillar protein

This research focused on the effects of L-arginine (Arg, 5 mM), transglutaminase (TG, E : S = 1 : 500), and the combination (Arg + TG) on the physicochemical properties and heat-induced gel performance of freeze-damaged myofibrillar protein (MP). The incorporation of Arg decreased the α-helix percentage (48.4%) and the mean particle size of freeze-damaged MP, as well as cooking loss (46.5%) and the overall textural characteristics of MP gels. The addition of TG reduced the α-helix content by 10.7% but significantly enhanced the crosslinking and heat-induced gel behavior of freeze-damaged MP, resulting in a slight reduction of cooking loss (17.7%) and the most ideal textural properties of MP gels. Although the presence of Arg remarkably suppressed the heat-induced development of storage modulus (G') and reduced the hardness of MP gels (by 13.4%), the combination (Arg + TG) showed the lower cooking loss and the improved textural characteristics, with the set gel displaying the most delicate and compact microstructure. These findings indicated that the combination of Arg and TG could be a potential strategy to enhance the gelling performance of freeze-damaged meat proteins.

Cryoprotective Roles of Carboxymethyl Chitosan during the Frozen Storage of Surimi: Protein Structures, Gel Behaviors and Edible Qualities

Carboxymethyl chitosan (CMCh) is an ampholytic chitosan derivative that manifests versatile applications in food industry, such as antibacterial ingredients and nutritional additives. However, its use as a cryoprotectant remains under-researched. In this study, the cryoprotective effect of CMCh oligosaccharide (CMCO) on frozen surimi (silver carp) was systematically investigated in terms of protein structures, gelling behaviors, and sensory qualities. CMCO (0.6%) was incorporated in the surimi before frozen storage (-18 °C for 60 days) while the commercial cryoprotectant (4% sucrose, 4% sorbitol) was used as a positive control. Results indicated that CMCO could inhibit the freezing-induced denaturation of myofibrillar protein, whose values of solubility, Ca2+-ATPase and sulfhydryl content were 24.8%, 64.7%, and 17.1% higher than the nonprotected sample, respectively, while the surface hydrophobicity was 21.6% lower. Accordingly, CMCO stabilized microstructure of the surimi gels associated with improved gel strength, viscoelasticity, water-holding capacities, and whiteness. Moreover, the cryoprotective effect of CMCO with higher degree of carboxymethyl substitution (DS: 1.2) was more pronounced than that of low-DS-CMCO (DS: 0.8). Frozen surimi treated with high-DS-CMCO achieved competitive gelling properties and sensory acceptability to those with the commercial counterpart. This study provided scientific insights into the development of ampholytic oligosaccharides as food cryoprotectants.

Effect of Active Coatings Containing Lippa citriodora Kunth. Essential Oil on Bacterial Diversity and Myofibrillar Proteins Degradation in Refrigerated Large Yellow Croaker

The research evaluated the effects of locust bean gum (LBG) and sodium alginate (SA) active coatings containing 0.15, 0.30 or 0.60% lemon verbena (Lippa citriodora Kunth.) essential oil (LVEO) on the bacterial diversity and myofibrillar proteins (MPs) of large yellow croaker during refrigerated storage at 4 °C for 18 days. Variability in the dominant bacterial community in different samples on the 0, 9th and 18th day was observed. Pseudomonas and Shewanella were the two major genera identified during refrigerated storage. At the beginning, the richness of Pseudomonas was about 37.31% and increased for control (CK) samples during refrigerated storage, however, the LVEO-treated samples increased sharply from day 0 to the 9th day and then decreased. LBG-SA coatings containing LVEO treatments significantly delayed MPs oxidation by retarding the formation of free carbonyl compounds and maintaining higher sulfhydryl content, higher Ca²⁺-ATPase activity, better organized secondary (higher contents of α-helix and β-sheet) and tertiary structures during refrigerated storage. The transmission electron microscope (TEM) images showed that the integrity of the sarcomere was damaged; the boundaries of the H-, A-, and I-bands, Z-disk, and M-line were fuzzy in the CK samples at the end of storage. However, the LVEO-treated samples were still regular in appearance with distinct dark A-bands, light I-bands, and Z-disk. In brief, LBG-SA active coatings containing LVEO treatments suggested a feasible method for protecting the MPs of large yellow croaker during refrigerated storage.

Effect of soluble soybean polysaccharides on freeze-denaturation and structure of myofibrillar protein of bighead carp surimi with liquid nitrogen freezing

This paper investigated the synergistic effect of 3% soluble soybean polysaccharides (SSPS) and liquid nitrogen freezing (-80 °C) on the freezing process and protein denaturation of bighead carp surimi. Freezing curve showed that liquid nitrogen freezing could significantly minimize the elapsed time of maximum-ice-crystal formation zone. Both liquid nitrogen freezing and SSPS were useful in preventing protein denaturation of surimi during 12-week frozen storage. Protein denaturation results indicated that SSPS-LNfreezing surimi1 had the highest protein solubility, Ca2+-ATPase activity and total sulfhydryl content. SDS-PAGE indicated that SSPS and liquid nitrogen freezing could effectively inhibit the decrease of myosin heavy chain concentration after 12 weeks of frozen storage. Raman spectra showed that tryptophan and tyrosine were exposed to polar microenvironment, the ɑ-helix and β-sheet turned into random coil and β-turn, and the conformation of disulfide bond changed from trans-gauche-trans (t-g-t) to gauche-gauche-trans (g-g-t). Either SSPS or liquid nitrogen freezing could mitigate these changes during frozen storage and a synergistic effect emerged on preventing myofibrillar protein denaturation and protein structure change. The combination of SSPS with liquid nitrogen freezing could be applied to freeze bighead carp surimi.

Effect of chitosans and chitooligosaccharides on the processing and storage quality of foods of animal and aquatic origin

Purpose

– The aim of the paper is to shed light on the use of chitosans and chitooligosaccharides as biopreservatives in various foods animal. Foods of animal and aquatic origin (milk, meat, fish, eggs, sea foods, etc) become contaminated with a wide range of microorganisms (bacteria, molds and yeasts) during harvesting, transporting, processing, handling and storage operations. Due to the perishable nature of these foods, their preservation is of utmost importance. Though many synthetic chemicals are available, yet their use is quite restricted due to their hazardous effects on human health.

Design/methodology/approach

– Within the domain of food industry, traditionally chitosan is used for biopreservation of foods, which is well known for its nutritional and medicinal properties in human nutrition. However, chitooligosaccharides also possess a number of nutraceutical and health promoting properties in addition to their preservative effect and shelf-life extension of foods. In this study, the comparative effects of both chitosan and chitooligosaccharides on preservation of foods of animal and aquatic origin have been summarized.

Findings

– Though chitosan has been extensively studied in various foods, yet the use of chitooligosaccharides has been relatively less explored. Chitooligosaccharides are bioactive molecules generated from chitosan and have several advantages over the traditional use of chitosan both in food products and on human health. But unfortunately, little or no literature is available on the use of chitooligosaccharides for preservation of some of the foods of animal origin. Notable examples in this category include cheese, beef, pork, chicken, fish, sea foods, etc.

Originality/value

– This paper focuses on the effects of chitosans and chitooligosaccharides on the processing and storage quality of foods of animal and aquatic origin, which offers a promising future for the development of functional foods.