Metabolomics ravels flavor compound formation and metabolite transformation in rapid fermentation of salt-free fish sauce from catfish frames induced by mixed microbial cultures.

This study demonstrates that the co-inoculation with Lactiplantibacillus plantarum, Pichia fermentans and Staphylococcus saprophyticus accelerates catfish frame fish sauce fermentation. Over a 3-day period, significant changes occurred in physicochemical properties, microbial profiles, flavor compounds, and metabolomic spectra. Notable increases in acidity coupled with decreases in glucose underscored the robust environmental adaptability of the employed microorganisms. A reduction in total amino acids, alongside a rise in umami amino acids, suggested flavor enhancement. GC-MS analysis identified 40 key volatile compounds, with esters and aldehydes crucial for aroma development. UPLC-QTOF-MS-based untargeted analysis identified 934 metabolites, with 377 differential metabolites being vital (VIP > 1.5, P < 0.05), including amino acids, peptides, organic acids, nucleic acids, and fatty acids. Metabolites linked to amino acid metabolism, particularly phenylalanine and arginine, were associated with fermentation duration. These findings offer a theoretical basis for optimizing flavor and quality in fish sauces from fish by-products through accelerated fermentation.

Oxidative regulation and cytoprotective effects of γ-polyglutamic acid on surimi sol subjected to freeze-thaw process.

Frozen surimi sol incline to protein oxidation, but the quality control strategies based on oxidation remain limited. Hence, the antioxidant and cryoprotective effects of γ-polyglutamic acid (γ-PGA) on freeze-thawed salt-dissolved myofibrillar protein (MP) sol were investigated. Results showed that γ-PGA could effectively regulate protein oxidation of MP sol during freeze-thawing with lower carbonyl contents and less oxidative cross-linking. Meanwhile, γ-PGA primely maintained sol protein structures, showing reduction of 15.28% of salt soluble protein contents at γ-PGA addition of 0.04% under unoxidized condition. Additionally, compared to the control group without oxidation treatment, cooking loss of heat-induced gel with 0.04% γ-PGA decreased by 47.19%, while gel strength obviously increased by 57.22% respectively. Overall, moderate γ-PGA addition (0.04%) could inhibit protein oxidation of sol, further improving frozen stability of sol through hydrogen bonds and hydrophobic interaction, but excessive γ-PGA was adverse to sol quality due to severe cross-linking between γ-PGA and MP.

Effects of different thermal methods and degrees on the flavor of channel catfish (Ictalurus punctatus) fillets: Fatty acids, volatile flavor and taste compounds.

The effects of different thermal processing conditions on the flavor profiles of channel catfish were evaluated in terms of fatty acids, volatile flavor and taste compounds using steaming, boiling, roasting, and microwaving with different degrees. After thermal processing, 72 volatile organic compounds were detected, including 20 hydrocarbons, 5 ketones, 20 aldehydes, 7 heterocyclic compounds, 12 alcohols and others. Meanwhile, the contents of unsaturated fatty acids like oleic acid and linoleic showed a significant decline due to their heat-sensitive properties. With regard to taste compounds, thermal processing contributed to umami amino acids and free nucleotides conversion, with the initial glutamate and IMP contents of 15.87 and 164.91 mg/100 g in raw samples mainly increasing by 2.8-10.3 and 14.4-105.5 mg/100 g in processed ones. Compared to other methods, microwaving had limited effects on flavor compounds, and steaming and roasting had better performance to improve the flavor complexity of channel catfish.

Insight into the role of lipids in odor changes of frozen grass carp (Ctenopharyngodon idella) based on lipidomics and GC-MS analysis: Impact of freeze-thaw cycles and heat treatment.

The role of lipids in changes of volatile organic compounds (VOCs) in grass carp during 1 month of frozen storage with different freeze-thaw cycles and subsequent heat treatment was investigated. Sixty VOCs were identified in all groups by SPME-GC-MS. Odor contents fluctuated along with the freeze-thaw cycles and heat treatment, and the highest odor content was observed in frozen sample without freeze-thaw cycles. Freeze-thaw and heat treatment significantly promoted the lipid oxidation and hydrolysis for all the groups(p<0.05). Lipid metabolites were analyzed using non-targeted lipidomics and could be well distinguished among different freeze-thaw groups and heat-treatment groups. A total of 10 key differential lipid molecules were annotated, involving 4 metabolic pathways related to lipid degradation and odor formation. Spearman correlation analysis showed that these key differential lipids were significantly related to the formation of key VOCs (p<0.05).

Kinetics and mechanisms of thermal deterioration in silver carp (Hypophthalmichtys molitrix) surimi gel quality under high-temperature sterilization.

BACKGROUND: The gelation properties of surimi gel under various high temperatures (115, 118, and 121 °C) and sterilization intensities (F0 values of 3-7 min) were systematically investigated. A kinetic model detailed quality changes during heat treatment through mathematical analysis, elucidating mechanisms for gel quality degradation. RESULTS: Increased sterilization intensity significantly reduced the quality characteristics of surimi gel. Compared to the gel without sterilization treatment, when the sterilization intensity was increased to 7 min, the gel strength of the groups treated at 115 °C, 118 °C, and 121 °C decreased by 68.35%, 51.4%, and 51.71%, respectively, and the water-holding capacity decreased by 24.87%, 16.85%, and 22.5%, respectively. The hardness, chewiness, and whiteness of the gel also significantly decreased, and the changes in these indicators all conformed to a first-order kinetic model. Activation energy of 291.52 kJ mol-1 highlighted gel strength as the least heat-resistant. At equivalent sterilization intensities, 115 °C exhibited the poorest gel quality, followed by 121 °C, with 118 °C showing relatively better gel quality. Increased T22 and decreased PT22 suggested heightened water mobility and transition of immobilized water within the gel into free water. Protein degradation, weakened disulfide bonds and hydrophobic interaction, and protein conformation changes collectively led to a rough and incoherent gel network structure with large fissures, as verified by the results of scanning electron microscopy. Correlation analysis indicated potential for precise control over surimi gel quality by modulating physicochemical attributes. CONCLUSION: The outcomes may be beneficial to improve the production and quality control of ready-to-eat surimi-based products. © 2024 Society of Chemical Industry.

Effects of Inoculating Autochthonous Starter Cultures on Changes of N-Nitrosamines and Their Precursors in Chinese Traditional Fermented Fish during In Vitro Human Digestion.

The objective of this research was to investigate the impact of inoculating autochthonous starter cultures on the alterations in microorganisms, biogenic amines, nitrite, and N-nitrosamines in Chinese traditional fermented fish products (CTFPs) during in vitro human digestion. The results revealed that gastric digestion significantly (p < 0.05) inhibited the proliferation of lactic acid bacteria, yeast, Staphylococcus, and Enterobacteriaceae, whereas various microorganisms proliferated extensively during small intestine digestion. Meanwhile, small intestine digestion could significantly increase (p < 0.05) levels of putrescine, cadaverine, and tyramine. The reduced content observed in inoculated fermentation groups suggests that starter cultures may have the ability to deplete biogenic amines in this digestion stage. Gastric digestion significantly (p < 0.05) inhibited nitrite accumulation in all CTFPs samples. Conversely, the nitrite content increased significantly (p < 0.05) in all groups during subsequent small intestine digestion. However, the rise in the inoculated fermentation groups was smaller than that observed in the spontaneous fermentation group, indicating a potentially positive role of inoculated fermentation in inhibiting nitrite accumulation during this phase. Additionally, gastric digestion significantly (p < 0.05) elevated the levels of N-nitrosodimethylamine (NDMA) and N-nitrosopiperidine in CTFPs. Inoculation with L. plantarum 120, S. cerevisiae 2018, and mixed starter cultures (L. plantarum 120, S. cerevisiae 2018, and S. xylosus 135 [1:1:1]) effectively increased the degree of depletion of NDMA during this digestion process.

Selection of texture-associated biomarkers in chilled and iced grass carp (Ctenopharyngodon idella) fillets via DIA-based proteomics.

Consumers care about the texture of fresh fish flesh, but a rapid quantitative analytical method for this has not been properly established. In this study, texture-associated biomarkers were selected by DIA-based proteomics for possible future application. Results indicated a significant decline in texture and moisture characteristics with extended storage under chilled and iced conditions, and flesh quality was categorized into three intervals. A total of 8 texture-associated biomarkers were identified in the chilled storage group, and 3 distinct ones in the iced storage group. Biomarkers were further refined based on their expression levels. Isobutyryl-CoA dehydrogenase, mitochondrial and [Phosphatase 2A protein]-leucine-carboxy methyltransferase were identified as effective texture-associated biomarkers for chilled fish, and Staphylococcal nuclease domain-containing protein 1 for iced fish. This study provided suitable proteins as indicators of fresh fish flesh texture, which could help establish a rapid and convenient texture testing method in future studies.

Uncovering quality changes of surimi-sol based products subjected to freeze-thaw process: The potential role of oxidative modification on salt-dissolved myofibrillar protein aggregation and gelling properties.

Frozen surimi quality generally correlates with oxidation, but impacts of protein oxidation on salt-dissolved myofibrillar protein (MP) sol in surimi remain unclear. Hence, physicochemical and gelling properties of MP sol with different oxidation degrees were investigated subjected to freeze-thaw cycles. Results showed that mild oxidation (≤1 mmol/L) improved unfrozen MP gel quality with lowest cooking loss (3.29 %) and highest hardness (829.76 N). Whereas, oxidized sol suffering freeze-thawing degenerated severely, showing reduction of 23.85 % of salt soluble protein contents with H2O2 concentrations of 10 mmol/L. Shearing before heating influenced gelling properties of freeze-thawed sol, depending on oxidation levels. Oxidized gel with shearing displayed disorganized network structures, whereas gel without shearing displayed relatively complete appearances without holes under high oxidation condition (10 mmol/L). Overall, freeze-thaw process aggravated denaturation extents of MP sol subjected to oxidation, further causing high water loss and yellow color of heat-induced gel, especially to gel with shearing.

Effect of different starch on masking fishy odor compounds.

Starch is a common ingredient to improve gel property of freshwater fish surimi, but the function of natural starch to mask fishy odor compounds in surimi products has not been investigated systematacially. Therefore, this study aimed to determine which natural starch could effectively mask fishy odor compounds and clarify their interaction by GC-MS, FT-IR spectroscopy, raman spectroscopy, X-ray diffraction, scanning electron microscopy and 13C nuclear magnetic resonance. The results showed that when the concentration, crystal type, amylose content, and dispersion degree of starch was 1 %, type C, 48 % (w/v), and 200 mesh with 0.88 span, the starch had the strongest masking effect on typical fishy odor compounds, namely hexanal, 1-Octen-3-ol, (E,E)-2,4-Heptadienal and (E)-2-Octenal. It indicated that complexation and hydrogen bonding both occurred between the fishy odor compounds and starch.

Influence of cellulose viscosity on the physical, mechanical, and barrier properties of the chitosan-based films.

This research paper presents a comprehensive investigation into developing biodegradable films for food packaging applications using chitosan (CN) in conjunction with three distinct types of cellulose (CE), each characterized by varying viscosities. The primary objective was to assess the influence of cellulose viscosity on the physical, mechanical, and barrier properties of the resulting films. The medium-viscosity cellulose imparted numerous advantageous qualities to the biodegradable films. These films exhibited optimal thickness (31 µm), ensuring versatility in food packaging while maintaining favorable mechanical properties, blending strength, and flexibility. Also, medium-viscosity cellulose significantly improved the films' barrier performance, particularly regarding oxygen permeability [1.80 × 10-6 (g.mm.m-2. s-1)]. Furthermore, the medium-viscosity cellulose contributed to superior moisture-related properties, including reduced water vapor permeability [14.80 × 10-9 (g.mm.m-2. s-1. Pa-1)], moisture content (13.22 %), and water solubility (22.87 %), while maintaining an appropriate degree of swelling (41.88 %). Moreover, the study employed advanced analytical techniques, including FTIR, XRD, and TGA, to provide critical insights into the films' chemical, structural, and thermal aspects. This research underscored the importance of the viscosity of film formulation materials as a crucial element in designing and efficiently producing films for food packaging.

Effect of sugar reduction on sensory characteristics of dried fish mince product.

BACKGROUND: Excessive sugar consumption has been linked to type 2 diabetes, obesity and other diseases. Therefore, it is indispensable to reduce sugar of food. However, the sensory characteristics of food are affected after sugar reduction (SR). Currently, SR has been reported in drinks, jams, candies, and other fruit related or sweet foods; but salty or protein related foods have not been explored, therefore there is a big gap that needs to be filled. RESULTS: Sensory scores of initial sweetness and sweetness reduced by 0.26 and 0.12 in 10% SR dried fish mince product compared with control, and there was a small difference between 25% SR (3.33) and 40% SR (3.09) samples. It also showed that 10% SR sample had a small reduction in sweetness value and free sugar content by 3.5% (0.42/11.9) and 7.8% (2.12/27.06) compared with control; while values in 25% SR sample decreased sharply but were not much different from 40% SR sample. Electronic nose results showed that SR had a small effect on odor. Texture analysis showed that texture properties of 25% SR sample were significantly different from control. CONCLUSIONS: Dried fish mince product with below 10% SR had a small difference on the sensory characteristics and there was a big change when SR was more than 20%. Dried fish mince product with 25% SR and 40% SR had no significant difference. SR had a small effect on odor, but had a great effect on texture properties, especially over 20% SR. © 2023 Society of Chemical Industry.

Study on the effect and mechanism of chicken breast on the gel properties of silver carp (Hypophthalmichtys molitrix) surimi.

BACKGROUND: Adding appropriate exogenous substances is an effective means to improve the quality of freshwater fish surimi. The present study investigated the effects of chicken breast on the gel properties of mixed minced meat products. RESULTS: With the increase in the proportion of chicken breast, the breaking force of mixed gels gradually increased. When the addition ratio was 30:70, the gel strength of mixed gels had the highest strength of 759.00 g cm-1 and also the highest water holding capacity of 87.36%. Compared with surimi gels (0:100), the hardness, adhesiveness and chewiness of mixed gels were significantly improved. The increase in the proportion of chicken breast increased the thermal stability of the mixed sol and improved the rheological properties of the mixed sol. When the proportion was 40:60, the area of immobile water (A22 ) in the mixed gel increased significantly, and the highest A22 was 3463.24. The hydrophobic interactions and disulfide bonds in the mixed gel were significantly increased as a result of the addition of chicken breast. The results of microstructure, electrophoresis and Raman spectroscopy indicated that the addition of chicken breast promoted the cross-linking of the proteins in mixed gels, which facilitated the transformation of the protein secondary structure from α-helical to ß-folded structure, thus forming a more uniform and orderly network structure. CONCLUSION: These results suggest that improving the gel properties of silver carp surimi by use of chicken breast has practical implications for the development of new blended products for surimi processing. © 2023 Society of Chemical Industry.

Neuroprotective effect of chitosan oligosaccharide on alcohol-induced hippocampal injury using proteomic analysis.

Alcoholism is a serious public health problem, and the abuse of drinking seriously damages the health of people. Chitosan oligosaccharides (COSs) are small-molecule oligosaccharides with amino groups that have many unique properties. The neuroprotective effect of COS on alcohol-induced hippocampal injury in Sprague-Dawley (SD) rats was investigated. The discrimination ratio of the COS group in the Y-maze experiment was 59.3% higher than that of the ETOH group. Meanwhile, the discrimination index was less than 0 in the ETOH group but greater than 0 in the COS group during the object recognition test. The cells in the COS group were more tightly arranged than those in the ETOH group. Proteomics was used to identify differentially expressed proteins in the hippocampus. There were 27 differentially expressed proteins in the COS and ETOH group for further bioinformatic analysis. There are three enriched pathway categories, namely, primary immunodeficiency, hedgehog signaling, and sulfur relay system. Next, sonic hedgehog signaling pathway-related proteins were verified through western blotting. The protein expression level of ß-arrestin-2 in the COS group was 2.85 times higher than that in the ETOH group. This work may contribute to understanding the underlying mechanism of the neuroprotective effect of COS against alcohol-induced hippocampal injury in SD rats.

L-histidine-assisted ultrasound improved physicochemical properties of myofibrillar proteins under reduced-salt condition - Investigation of underlying mechanisms.

The effects of the L-hisdine (L-His)-assisted ultrasound on physicochemical characteristics and conformation of myofibrillar protein (MP) under reduced-salt condition were investigated using spectroscopic analysis, and the binding mechanism between L-His and MP was further elucidated through molecular docking and molecular dynamics (MD) simulations. UV second derivative spectra and intrinsic Try fluorescence spectra revealed that L-His formed a complex with MP and altered the microenvironment of MP. After L-His-assisted ultrasound treatment, MP showed smaller particle size, higher solubility, and more uniform atomic force microscopy image due to the decrease of α-helix content and the subsequent increase in zeta potential, active sulfhydryl content, and surface hydrophobicity. Molecular docking and MD simulations demonstrated the optimal docking pose (minimum binding affinity of -6.78 kcal/mol) and revealed hydrophobic interactions and hydrogen bonds as the main interaction forces between L-His and MP, with several residues (ILE-464, ILE-480, THR-483, ASN-484, GLY-466, ASP-463, PHE-246) identified as binding sites.

The inhibition mechanism of nanoparticles-loading bilayer film on texture deterioration of refrigerated carp fillets from the perspective of protein changes and exudates.

Herein, the protective pattern of bilayer film on the texture stability of fillets was discussed in terms of endogenous enzyme activity, as well as protein oxidation and degradation. The texture properties of fillets wrapped with nanoparticles (NPs) bilayer film were greatly improved. NPs film delayed protein oxidation by inhibiting the formation of disulfide bond and carbonyl group as evidenced by the increase of α-helix ratio (43.02%) and the decrease of random coil ratio (15.87%). The protein degradation degree of fillets treated with NPs film was lower than that of control group, specifically with a more regular protein structure. The exudates accelerated the degradation of protein, while NPs film effectively absorbed exudates to delay protein degradation. Overall, the active agents in the film were released into the fillets to play an antioxidant and antibacterial roles, and the inner layer of film could absorb exudates, thus maintaining the texture characteristics of fillets.

Synthesis, characterization, and anticancer activity of protamine sulfate stabilized selenium nanoparticles.

Selenium nanoparticles (SeNPs) have attracted much recent interest as nutraceuticals, while they face great challenges, such as poor stability and low cellular uptake efficiency. This study introduced a facile approach to synthesizing protamine sulfate (PS) functionalized selenium nanoparticles (PS-SeNPs) by using PS as a surface decorator. The monodisperse spherical PS-SeNPs with a particle size of 130 nm and a ζ-potential of +31 mV were ligated with PS through Se-N, Se-O bonds, and physical adsorption, which exhibits excellent physical stability against pH, temperature, and storage time. The positive surface charge of PS-SeNPs contributed to the enhancement of cellular uptake efficiency by endocytosis, which was 3-times higher than bare SeNPs. Compared to SeNPs (IC50 = 17.675 µg/mL), PS-SeNPs could dramatically inhibit the proliferation of HepG2 cells with an IC50 value of 5.507 µg/mL, as reflected by the induction of apoptosis, S phase arresting, overproduction of intracellular ROS, and depolarization of mitochondria membrane. Overall, these results demonstrated the great potential of PS-SeNPs that can be applied as a functional ingredient in foods and nutraceuticals.

The migration and loss of water in emulsified surimi gels prepared with different phase states of lipids: Effect of freeze-thawing treatments.

The freeze-thawing (FT) stability generally correlates well with the economic value and acceptability of frozen surimi-based products. However, quality changes of emulsified surimi gels under FT conditions are still unclear. Therefore, the gel properties of samples with different phase states of lipids (lard, lard + soybean oil, and soybean oil) were investigated at FT conditions. Results showed that the soybean oil evidently improved the rheological behaviors of sols/gels compared to the lard group. The moisture content of samples with different lipids decreased by 2.40%-2.71% after 4 FT cycles. With increasing FT cycles, the water-holding capacity decreased accompanied by the increase of cooking loss. Spin-spin relaxation spectra and hydrogen proton density images proved the occurrence of water migration of gels during these processes. Better gel integrity was observed in samples consisting of soybean oil, where the proportion of pores was lower than those with lard regardless of FT treatments. Additionally, the intermolecular forces of gels also changed under FT treatments. There results suggested that the lipids with different phase states affected the migration and loss of water in emulsified surimi gels under FT cycles. PRACTICAL APPLICATION: The quality changes of heating-induced surimi gel products under frozen storage have been ignored, especially the emulsified surimi gels. This study discloses the changes of the gel properties in emulsified gel products with different phase states of lipids after FT treatments, which provides critical insights into the quality improvement of this novel emulsified surimi product during processing, storage, and transportation.

Influence of the Enzymatic Hydrolysis Using Flavourzyme Enzyme on Functional, Secondary Structure, and Antioxidant Characteristics of Protein Hydrolysates Produced from Bighead Carp (Hypophthalmichthys nobilis).

In the current study, bighead carp fish were used in conjunction with the flavourzyme enzyme to obtain (FPH) fish protein hydrolysates. The optimum conditions of the hydrolysis process included an enzyme/substrate ratio of 4% and a temperature of 50 °C and pH of 6.5. The hydrolysis time was studied and investigated at 1, 3, and 6 h, and the (DH) degree of hydrolysis was recorded at 16.56%, 22.23%, and 25.48%, respectively. The greatest yield value was 17.83% at DH 25.48%. By increasing the DH up to 25.48%, the crude protein and total amino acid composition of the hydrolysate were 88.19% and 86.03%, respectively. Moreover, more peptides with low molecular weight were formed during hydrolysis, which could enhance the functional properties of FPH, particularly the solubility property ranging from 85% to 97%. FTIR analysis revealed that enzymatic hydrolysis impacted the protein's secondary structure, as indicated by a remarkable wavelength of amide bands. Additionally, antioxidant activities were investigated and showed high activity of DDPH radical scavenging, and hydroxyl radical scavenging demonstrated remarkable activity. The current findings demonstrate that the functional, structural, and antioxidant characteristics of FPH might make it an excellent source of protein and suggest potential applications in the food industry.

The protective pattern of chitosan-based active coating on texture stabilization of refrigerated carp fillets from the perspective of proteolysis.

Herein, the protective pattern of chitosan coating enriched with green tea extract on texture stabilization of refrigerated grass carp fillets was explored. In general, higher shear force and lower endogenous enzyme activities were observed in coated fillets, with the max. level of cathepsins and calpain decreasing by 30.2 âˆ¼ 39.6 % when compared to the control during storage. Meanwhile, the coating reduced protein composition changes and accumulation of protein degradation products. According to label-free proteomic analysis, the proteome closer to fresh sample was observed in coated fillets than that of the control, as supported by PCA and hierarchical cluster analysis. Meanwhile, 33 differential proteins involved in tissue structure, protein phosphorylation and protein turnover were further screened out, and most DAPs showed up-regulation in coated fillets compared to the control on day 12. Presumably, the coating modulated endogenous enzyme-induced myofibrillar protein degradation and protein phosphorylation level, thereby stabilizing the texture properties of refrigerated fillets.