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Summary: Brown stain is a major problem for tuna during storage. This study aimed to investigate the impact of antioxidants on myoglobin oxidation and the promotion of metmyoglobin (MetMb) reduction in tuna slices. Response surface methodology (RSM) was used to optimise the formula of the compound antioxidant in yellowfin tuna (YFT) slices, with the percentage of MetMb as the response value. The ratios of ε‐polylysine, sodium lactate and D‐sodium ascorbate were 0.43%, 2.21% and 2.71%, respectively. The interactions between sodium lactate and D‐sodium ascorbate had a greater impact on the percentage of MetMb. Then, verification experiments were conducted, and the results revealed that the samples treated with compound antioxidants had higher a* values, total sulfhydryl content, Ca2+‐ATPase activity, total reducing activity (TRA) and MetMb‐reducing activity (MRA) and lower percentages of MetMb and carbonyl contents than did the control samples. It also helps to maintain the stability of the NADH/NAD+ ratio, which contributes to facilitating MetMb reduction. The results showed that the compound antioxidant significantly inhibited myoglobin oxidation, promoted the reduction of MetMb in tuna slices and significantly enhanced the myoglobin stability of refrigerated YFT slices. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Summary: The impact of κ‐carrageenan on the physicochemical structural characteristics of ready‐to‐eat (RTE) Antarctic krill surimi gel (AKSG) was investigated. The modifications in chemical bonding, protein secondary structure, protein composition and microscopic morphology were compared in both gels with and without κ‐carrageenan. According to the findings, adding 4% (w/w) κ‐carrageenan could reduce the cooking loss of AKSG significantly (P < 0.05), enhance the WHC and textural quality of AKSG and RTE AKSG and increase the amount of hydrophobic and disulfide bonds so that the secondary structure of Antarctic krill proteins could be shifted to the β‐sheet. However, there was little impact on the composition of the protein molecules according to the SDS‐PAGE. In addition, the usage of κ‐carrageenan significantly alleviated the disruption of the protein gel network caused by high‐temperature and high‐pressure treatments (P < 0.05). Therefore, applying κ‐carrageenan could effectively enhance the gel quality of RTE AKSG. [ABSTRACT FROM AUTHOR]

Summary: The effects of different grilling temperatures (220 °C, 250 °C, 280 °C, 310 °C) reaching the central temperature of 70 °C on heterocyclic amines (HAs) formation, moisture content, cooking loss, texture, colour, and sensory properties of grilled grass carp (Ctenopharyngodon idella) were investigated. The grilling condition significantly (P < 0.05) affected cooking loss, moisture content, heterocyclic amines (HAs) formation, texture, colour and sensory properties. The results showed that 5 kinds of free and 9 kinds of protein‐bound heterocyclic amines were detected. The total amount of protein‐bound heterocyclic amines was much higher than that of the free state. Harman and Norharman, belonging to β‐carboline, constituted over 80% of the total content of heterocyclic amines. Considering the HAs formation and quality attributes, when the grilling condition was 280 °C for 10 min, the total content of HAs was the lowest, and the fish had moderate moisture content, firm texture, bright colour, and high sensory evaluation score. [ABSTRACT FROM AUTHOR]

Summary: Textural deterioration is a severe problem in fish industry. In order to study the role of structural proteins in refrigerated grass carp, myofibrillar proteins and collagen degradation were investigated at different stages. Results revealed that connective tissues of fish muscle disintegrated from day 1, failing to hold muscle myotomes together, with a decrease of shear force. Meanwhile, collagen solubility increased from day 1 and degradation of nebulin was observed after 3 days, while there was no obvious change in the bands of myosin heavy chain and actin. Furthermore, Pearson coefficient analysis revealed that insoluble collagen (ISC) and nebulin were significantly correlated with shear force. Negative correlation was established between drip loss and contributing factors (ISC, titin and nebulin). All results suggested that textural loss of post‐mortem grass carp fillets was mainly mediated by the degradation of collagen and to a lesser extent by myofibrillar proteins at the early storage. [ABSTRACT FROM AUTHOR]

Summary: Silver carp myofibrillar proteins (MP) with different moleculars states were constructed by the addition of NaCl and fracture degree of muscle fibres. Results showed that salt‐dissolved MP (P+) under unfrozen and oxidised state showed higher oxidation degree with higher carbonyl (3.42 nmol mg−1) and dityrosine contents (25.98 a.u.) (P < 0.05) compared with saltless‐polymeric MP (P) and salt‐induced swelling MP (F+) due to addition of salt and broken muscle fibres. After oxidative and freeze–thaw process, P+ group also exhibited more cross‐linking as evidenced by turbidity (0.73), solubility (64.96%) and SDS‐PAGE, but unordered aggregates in P group increased probably due to severe frozen denaturation. Moreover, F+ group of salt‐induced swelling MP from intact muscle fibres suffered less structural damages with higher fluorescence intensity (668.41 a.u.) and higher α‐helix contents (15.56%). Overall, Fish‐ Hua of salt‐dissolved MP had a higher oxidation level and NaCl contributed to improve freeze–thaw stability of MP during freeze–thaw process. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 β‐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. [ABSTRACT FROM AUTHOR]

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 β‐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. [ABSTRACT FROM AUTHOR]

The study aimed to assess the effects of different cooking temperatures (90, 93, 95, 98, and 100 ℃) and time (1, 3, 5, 7, and 9 min) on the physicochemical, textural, microstructural, and microbiological properties of fresh whole-limb crayfish. The differential scanning calorimetric (DSC) curve and heat transfer curves showed that the protein in the crayfish muscles was completely denatured after 3 min of heating. Meanwhile, increasing cooking temperatures could result in a faster heat transfer rate, better shell color, and more moisture loss. The hardness and chewiness of crayfish muscle increased significantly within 3 min of heating and then decreased slightly in the later phase (P > 0.05). Crayfish cooked at 93 to 95 ℃ for 3 to 5 min showed the highest hardness about 330–373 g. With increasing heating time, the microstructure of muscle fibers changed from a compact state to a loose state due to water loss and the damage to the endomuscular membrane. Higher temperature resulted in markedly lower TVC compared to 90 ℃. This research provided a reliable reference for cooking and processing crayfish. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Summary: In this study, the effect of several additives, including CaCl2, L‐histidine (L‐His) and sodium pyrophosphate, incorporation with ultrasound treatment on the gel properties of reduced‐salt surimi, was tested. Among these additives and ultrasound treatment times, 0.1% L‐His and 10‐min ultrasound alone were determined to be more effective in increasing the gel strength, water‐holding capacity (WHC) and reducing cooking loss (CL) of reduced‐salt (1% NaCl) surimi gel. L‐His and ultrasound alone or in combination could facilitate the transition of α‐helix to β‐sheet and random coil, thereby increasing hydrophobic interactions and disulfide bonds in the gel. The results of low‐field nuclear magnetic resonance showed that the proportion of immobilised water (PT22) in reduced‐salt surimi gel was significantly increased (P < 0.05). The storage modulus (G′) of reduced‐salt surimi gel was also increased. Moreover, scanning electron microscopy results showed that the gels treated with L‐His and ultrasound alone or in combination had a more compact network structure. Notably, the synergy of L‐His combined ultrasound treatment was the most effective in enhancing the characteristics of reduced‐salt surimi gel. [ABSTRACT FROM AUTHOR]

BACKGROUND: Apoptosis activation is an essential research to reveal the triggering mechanism of flesh quality deterioration. This study was aimed at explaining apoptotic mechanism of postmortem fish in terms of caspases activation, cytochrome c (cyt‐c) release, B‐cell lymphoma 2 (Bcl‐2) and Bcl2‐associated X (Bax) protein levels, transcriptional levels of its molecules, and apoptosis‐inducing factor (AIF) translocation at 4 °C for 5 days. RESULTS: Activation of caspase‐9, caspase‐8, caspase‐3 and the release of mitochondrial cyt‐c were observed during storage. The decreased Bcl‐2 protein levels, increased Bax protein expressions and Bax/Bcl‐2 ratio were major steps for inducing apoptosis. Collectively, transcriptional regulation of Fas ligand (FasL), apoptotic protease activating factor‐1 (Apaf‐1), inhibitors of apoptosis proteins (IAPs), myeloid cell leukemia‐1 (Mcl‐1), c‐Jun N‐terminal kinase (JNK) and p38 mitogen‐activated protein kinase (MAPK) indicated that extrinsic apoptotic pathways (FasL/caspase‐8/caspase‐3) and intrinsic pathway [(JNK and p38 MAPK)/(Bcl‐2, Bax and Mcl‐1)/cyt‐c/Apaf‐1/caspase‐9/caspase‐3] were involved in apoptotic process. Mitochondrial AIF translocation to nuclear indicated that AIF mediated caspase‐independent pathway. CONCLUSION: Therefore, transcriptional and translational alterations of multiple signaling molecules acted important roles in regulating apoptosis activation in postmortem process. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Alterations of apoptosis have notable influences on flesh quality, but the mechanism is still unclear. Thus, apoptotic behaviors and related triggering mechanisms need to be explored. Fish muscle was prepared and stored at 4 °C for 0, 24, 48, 72, 96, and 120 h for apoptosis analysis. Results showed that positive apoptotic nuclei were positively correlated with drop loss and negatively correlated with shear force and water holding capacity (p < 0.05). Results showed that the triggering apoptotic mechanisms were involved with enhanced transcriptional levels of caspase-2, 3, 7, 8, and 9 through mitochondria and death receptor pathways in the muscle of grass carp. The decreased ATP content, changed cytochrome c redox state, increased protein levels of HSP27 and HSP 90, and enhanced activity of cathepsin (B, L, and D), calpain, and serine proteinase were involved in apoptosis activations. Results indicated that caspases, energy metabolism, cytochrome c redox state, heat shock protein expressions, and protease activities played critical roles in apoptosis alterations in carp muscle during refrigerated storage. [ABSTRACT FROM AUTHOR]

Summary: This study investigated the effects of different NaCl substitutes on the gel properties, physicochemical properties, and sensory attributes of shrimp surimi gel to produce high‐quality reduced‐salt shrimp surimi gel. The results showed that CaCl2, calcium ascorbate (Vc‐Ca), and L‐arginine (L‐Arg) could significantly improve the gel strength and texture of shrimp surimi gel compared to NaCl. The addition of CaCl2, Vc‐Ca, and L‐Arg significantly increased the number of disulphide bonds and the content of β‐sheet structures compared to NaCl. The electrophoretic analysis revealed that CaCl2, Vc‐Ca, and L‐Arg had protective effects on the myosin heavy chain during thermal gelation. Additionally, CaCl2 and L‐Arg promoted the cross‐linking of myofibrillar proteins to form the denser and less porous microstructures, and thus improved the gel properties of shrimp surimi gel. In general, the introduction of L‐Arg as a substitute for NaCl acquired the best gel properties and sensory attributes of shrimp surimi gels, followed by CaCl2 and Vc‐Ca. [ABSTRACT FROM AUTHOR]

To understand the effect of the interaction between wheat starch (W S) and wheat gluten (W G) on batter characteristics and oil penetration of deep-fried breaded fish nuggets, batters were prepared using a W S and W G blend at the ratios of 15 : 1, 13 : 1, 11 : 1, 9 : 1, and 7 : 1 w / w , respectively, and batter-breaded fish nuggets (BBFNs) were fried at 170°C for 40 s followed by 190°C for 30 s. Moisture adsorption isotherms of W S and W G , viscosity, rheological behavior, and calorimetric properties of the batters were measured, and pick-up of BBFNs, thermogravimetric properties of the crust, and oil transport were investigated. The moisture absorption capacity of W G was higher than W S at a low water activity (0.04–0.65), while the opposite trend was observed at a highwater activity (0.65–0.88). As the proportion of W S decreased, the viscosity, G " and tan δ of batter, pick-up of BBFNs, temperature and enthalpy change (ΔH) of protein denaturation and W S gelatinization, and oil penetration of BBFNs during deep-fat frying, which are decreased until reaching a minimum value at the ratio of 11 : 1 w / w , then increased (p < 0.05). However, G' of batter and thermogravimetry temperatures of crust exhibited the opposite trend. These results proved that the W S – W G interaction significantly affected the batter characteristics and oil penetration of BBFNs during deep-fat frying, which can be used to guide the manufacturing of low-fat fried BBFNs. [ABSTRACT FROM AUTHOR]

Summary: Although the characterisation of volatile compounds in silver carp (Hypophthalmichthys molitrix) have been studied, their respective contribution to specific odour feeling was unclear. Therefore, an investigation was made in this study by big data mining, solid phase microextraction‐gas chromatography–mass spectrometry (SPME‐GC–MS), odour activity values (OAVs), odour recombination in surimi models and omission experiment. The results demonstrated that 91 volatile compounds were obtained by data mining and 62 volatile compounds were identified by instrumental analysis. Among them, twenty‐one volatile compounds were initially selected for the construction of the surimi model. The odour recombination and omission experiment confirmed that characteristic odour of silver carp surimi were hexanal (fishy, grassy), octanal (grassy, fatty), (E)‐2‐octenal (fishy), nonanal (grassy, fatty), (E)‐2‐nonanal (fatty, grass), (E,E)‐2,4‐heptadienal (fishy), 1‐hexanol (grassy) and 1‐octen‐3‐ol (mushroom). This study specified distinct silver carp surimi odour with definite compounds. [ABSTRACT FROM AUTHOR]

Summary: The disruption of structural integrity could affect flesh quality changes. This study investigated the disruption of muscle integrity and the affecting factors in postmortem fish at 4 °C for 5 days storage. Haematoxylin–eosin staining indicated that profound disruption of structural integrity was observed for the changes of dissolved nucleus, irregular shape of myofibrils and loose attachment. The increased activities of β‐N‐acetyl‐glucosaminidase (NAG) and α‐Glucosidase (AG) enzymes confirmed the profound disruption of integrity in postmortem muscle. The abnormal up‐regulated gene expressions of claudin‐11, claudin‐12, claudin‐15a, claudin‐15b and myosin light chain kinase (MLCK) implied the disrupted intercellular integrity. The impaired cellular integrity and the increased oxidative damage was due to the decreased antioxidant capacity, which was regulated by the decreased transcriptional levels of antioxidant enzymes. Collectively, this study provided a partial molecular mechanisms for the disruption of structural integrity and the changes of flesh quality in postmortem fish muscle. [ABSTRACT FROM AUTHOR]

Globally, fish processing industries are much concerned to produce fish proteins for the fulfilment of the nutritive requirements of human being. More than 60% fish by-products, including liver, head, skin, roes, viscera, and bones that the richest source of proteins, and these are processed to obtain valuable food products in different industries. Numerous studies have proved that fish proteins have a great potential to reduce the risks of cancer, aging, diabetics, and cardiovascular diseases. Their functional properties such as water and oil holding, film-forming, emulsification, solubility, and gelling capacities, which have increased their importance for the development of functional foods. So, this review is focused on different kinds of sources, extraction methods, and functional properties of fish proteins, also their utilization as functional bioactive compounds in the production of fish protein-enriched food products. [ABSTRACT FROM AUTHOR]

BACKGROUND: Textural deterioration is a serious problem in chilled fish flesh. Cysteine proteinases are proposed to participate in disintegration of collagen fibers during this process, while its mechanism remains elusive. In the present study, a cysteine proteinase was purified from grass carp muscle and identified by mass spectrometry, and its effect on structural changes of collagen fibers was investigated. RESULTS: During storage at 4 °C, cysteine proteinase activity in fillets increased to 1.53‐fold at day 5 and maintained a high level later, and this variable was related to a decline in shear force and an increase in drip loss. A 29 kDa cysteine proteinase was purified through ammonium sulfate precipitation and column chromatography, and identified as cathepsin L. Cathepsin L caused collagen fibers to partly disintegrate into fibril bundles and individual fibrils at 48 h, while the triple helical structure of collagen molecules remained stable. Release of soluble proteins and glycosaminoglycans from cathepsin L‐treated collagen fibers was time dependent, coinciding with a release of 4.12 ± 0.13% and 8.57 ± 0.03% at 48 h respectively. However, 0.85 ± 0.02% of hydroxyproline was freed from cathepsin L‐treated collagen fibers at 48 h. Furthermore, scanning electron microscopy revealed that the inhibitory effect of cathepsin L could retard the destruction of intramuscular connective tissues (IMCTs). CONCLUSION: These results indicated that cathepsin L might be involved in collagen fiber breakdown by degrading collagen‐associated proteoglycans during textural deterioration of grass carp. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

As an essential micronutrient, selenium participates in numerous life processes and plays a key role in human health. In the past decade, selenium nanoparticles (SeNPs) have attracted great attention due to their excellent functionality for potential applications in pharmaceuticals. However, the utilization of SeNPs has been restricted by their instability and low targeting ability. Since the existing reviews mainly focused on the applications of SeNPs, this review highlights the synthesis of SeNPs and the strategies to improve their stability and targeting ability through surface functionalization. In addition, the utilization of functionalized SeNPs for the single and co-delivery of drugs or genes to achieve the combination of therapy are also presented, with the emphasis on the potential mechanism. The current challenges and prospects of functionalized SeNPs are also summarized. This review may provide valuable information for the design of novel functionalized SeNPs and promote their future application in cancer therapy. [ABSTRACT FROM AUTHOR]

This study discovered a novel chitosanase from Penicillium oxalicum M2 based on a new screening strategy. An extracellular chitosanase was isolated and purified from the fermentation broth of Penicillium oxalicum M2. A 19.34-fold purification was achieved on a cation exchange column. Using sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis, chitosanase was determined at approximately 42 kDa without any subunits. The sequence of peptide in the protein was identified as SALNKNYITNFSTLR by MALTI-TOF/TOF MS. The maximum catalytic activity of the purified enzyme was 60.45 U/mg at the optimum pH and temperature of 5.5 and 60 °C. The enzyme activity held stability in the range of 35–50 °C and pH 3–4.5. Ca2+, Mn2+, non-ionic surfactants (Tween 20/40/60/80 and Trition X-100) and some common reducing agents (DTT and β-ME) could significantly activate chitosanase. The purified enzyme showed rigorous specificity to chitosan as a substrate. The hydrolysate in the final stage of hydrolysis consisted of chitooligosaccharides with a degree of polymerization ranging from 2 to 5 and without glucosamine or acetylglucosamine. The monomeric enzyme obtained by one-step purification reveal applications potential in sugar industry, and expanded our understanding of the GH75 family chitosanases simultaneously. [ABSTRACT FROM AUTHOR]

Summary: One of the most worrisome problems with frozen fish is its undesirable softening texture, due in part to the alteration of fish protein structure. Therefore, a new immersion freezing (IF) technology with the edible medium, which was proven to improve food freezing speed and quality, was compared with air blast freezing (AF) and liquid nitrogen freezing (LNF) on the scope of protein structure. Protein fractions, structure, chemical bonds and particle size of the grass carp muscle were used as indicators. At the end of 24 weeks of frozen storage, the content of salt‐soluble protein in IF (106.22 ± 1.01 mg g−1 meat) was significantly higher than that of AF (90.77 ± 1.11 mg g−1 meat) and LNF (97.44 ± 1.40 mg g−1 meat) (P < 0.05). Compared to AF, the α‐helix content of IF and LNF was higher, the content of β‐turn and random coil was lower, while no statistical difference was detected in IF and LNF groups (P < 0.05). Meanwhile, the intrinsic fluorescence intensity, ionic bonding and hydrogen bonding in IF were significantly higher than in AF. The lowest value of D[3,2] was observed in the IF group after 24 weeks storage. Therefore, IF is an effective approach to reducing protein denaturation and can be adopted as an alternative freezing method. [ABSTRACT FROM AUTHOR]

Summary: This study was designed to evaluate the effect of different cooking methods on the protein digestion characteristics of channel fish (Ietalurus punetaus). The channel fish muscles were subjected to different cooking methods, namely boiling, steaming and roasting and were subjected to in vitro gastrointestinal digestion simulation using raw fish as a control. All the cooking methods increased the protein digestibility (1.60–8.28%) and decreased the protein particle size at the end of the gastrointestinal digestion. The highest protein digestibility (66.78%) and the smallest protein particle size values (600.7 nm) were observed for the steamed group. Samples which were steam cooked showed lowest β‐sheet content (9.63 ± 0.81%) and were accompanied with moderate protein oxidation. As the core temperature increased from 40°C to 90°C, protein oxidation increased significantly (P < 0.05) with the increase of carbonyl groups and Schiff bases and decrease of sulfhydryl groups in all cooked groups. Based on the results, steaming was recommended as the best methods of cooking channel fish for improved protein digestibility. [ABSTRACT FROM AUTHOR]

Effects of two thermal treatments (sterilization at 118°C and pasteurization at 90°C) and acidification on the color, texture, chemical composition, and microstructure of high‐moisture laver were investigated. Results showed that the reddish‐purple of laver faded to varying degrees after heating due to rapid degradation of phycoerythrin. With increasing heating time, the a* value gradually decreased accompanied by the increase in b* value, and the color changed to yellow‐green. Besides, the hardness and toughness gradually decreased, while the adhesiveness increased. Microstructure and soluble sugar results indicated that the cell tissue of the laver was destroyed after intensive heating. Compared to sterilization, laver subjected to pasteurization at 90°C exhibited better texture and color. Intensive thermal processing accelerated quality deterioration as evidenced by pigment degradation, cell rupture, and increase in soluble substances. The combination of acidification (pH < 4.6) with mild heat treatment contributed to better quality retention of ready‐to‐eat lavers with higher moisture. Practical applications: Since most of the existing laver products in the market are dry, the development of high‐quality wet laver products has attracted attention. However, due to the extremely thin leaves and soft texture, the color and texture of laver are prone to deterioration during the heat sterilization process. Understanding the quality changes of laver under typical sterilization conditions is conducive for exploring solutions. The present study clarifies the effects of heat treatment and acidification on the characteristics of high‐moisture laver, which serves as a foundation for the future development of instant wet laver products that can meet both safety and palatability, and provides theoretical guidance for the seaweed processing industry. [ABSTRACT FROM AUTHOR]

Chitosan is obtained from chitin and considered to be one of the most abundant natural polysaccharides. Due to its functional activity, chitosan has received intense and growing interest in terms of applications for food preservation over the last half-century. Compared with earlier studies, recent research has increasingly focused on the exploration of preservation mechanism as well as the targeted inhibition with higher efficiency, which is fueled by availability of more active composite ingredients and integration of more technologies, and gradually perceived as "chitosan-based biofilm preservation." In this Review, we comprehensively summarize the potential antimicrobial mechanisms or hypotheses of chitosan and its widely compounded ingredients, as well as their impacts on endogenous enzymes, oxidation and/or gas barriers. The strategies used for enhancing active function of the film-forming system and subsequent film fabrication processes including direct coating, bioactive packaging film and layer-by-layer assembly are introduced. Finally, future development of chitosan-based bioactive film is also proposed to broaden its application boundaries. Generally, our goal is that this Review is easily accessible and instructive for whose new to the field, as well as hope to advance to the filed forward. [ABSTRACT FROM AUTHOR]

The effects of high‐temperature treatments (100–125 °C) on the properties of silver carp surimi gel were studied. The results showed that the gel strength and water holding capacity (WHC) of surimi gel decreased significantly (P < 0.05), with the increase of heating temperature and the prolongation of heating time, and the higher the temperature, the greater the decrease trend. Hydrophobic interaction and disulphide bonds decreased significantly, while ionic bonds increased significantly (P < 0.05), as well as β‐sheet increased while β‐turn and coil decreased significantly, which confirmed the changes of protein secondary structure caused by high‐temperature treatments. Myosin heavy chain (MHC) and actin bands gradually narrowed, and the production of new bands larger than 250 kDa by SDS‐PAGE showed the aggregation and cross‐linking reaction of proteins. However, the increased band intensity of 50–75 kDa and the increase of trichloroacetic acid (TCA) soluble peptides showed the degradation of proteins. The decrease of PT22 and the increase of PT23 indicated the conversion of immobilised water to free water in the gel matrix. In conclusion, high‐temperature heating caused the changes of protein secondary structure as well as chemical forces and water conversion, resulting in protein denaturation, aggregation, cross‐linking and degradation, forming a loosen and irregular gel network. [ABSTRACT FROM AUTHOR]

Summary: This study aimed to investigate the effects of antibacterial agent ultrasonic immersion on the quality of salted casings in terms of microorganism, physicochemical characters and structure characteristics. The results showed that citric acid immersion had the most significant effect as compared to that of control samples, with a reduction of 1.00, 1.65 and 1.66 log CFU g−1 in Staphylococcus, Halophile and Psychrophiles compared to control samples respectively. Citric acid and tea polyphenol treatment increased the elongation at break of casings by 11.3% and 10.4%, and the most significant increase in the tensile strength of samples with chitosan oligosaccharide was 13.7%. Meanwhile, all samples were not discriminative in colour, collagen solubility, water solubility, thermal swelling and thermal shrinking rate. Furthermore, a compact and dense casing surfaces found by the scanning electron microscopy (SEM) images after antibacterial agent treatment. Therefore, antibacterial agent immersion has the potential to control microorganisms' growth, improve mechanical properties and extend the application field of salted casings. [ABSTRACT FROM AUTHOR]

The production of fish protein hydrolysates from bighead carp (Hypophthalmichthys nobilis) using ficin enzymes was achieved in optimal conditions of 3% enzyme/substrate ratio, 40 °C temperature, and pH 6. Three different hydrolysis times, 1, 3, and 6 h, were investigated, and their degree of hydrolysis (DH) values were 13.36%, 17.09%, and 20.15%, respectively. The hydrolysate yield values increased with DH increase, and the highest yield was obtained at DH 20.15%. The crude protein content increased from 80.58% to 85.27%, and amino acid compositions increased from 78.33% to 83.07%. The peptides formed during hydrolysis indicated low molecular weight that might improve functional characteristics of fish protein hydrolysates, including protein solubility, which ranged from 84.88% to 95.48% for all hydrolysates. The thermal degradation of hydrolysates occurred from 160 to 168 °C with intensive endothermic peaks. Results revealed that oil holding capacity was higher at DH 13.36%; water holding capacity was higher when DH increased. Hence, fish protein hydrolysates (FPH) from bighead carp have improved functional properties, and can be utilized as supplements and excellent protein sources in various uses in food applications. [ABSTRACT FROM AUTHOR]

Summary: The physicochemical and microbiological parameters of postmortem crayfish stored at 4 °C and 25 °C were evaluated in order to reduce safety risks of crayfish from temperature abuse during transportation and storage. Results showed that hepatopancreas of postmortem crayfish had significantly higher contents of total volatile basic nitrogen, biogenic amines (BAs) and higher microbial loads than tail meat, regardless of storage temperature. Enterobacteriaceae and Pseudomonas counts reached log 6.41 log10 CFU g−1 and 6.31 log10 CFU g−1 in hepatopancreas of crayfish at 25 ℃ for 6 h. Putrescine and cadaverine were the main BAs in tail meat with levels of 28.18 ± 0.73 mg kg−1 and 187.32 ± 3.57 mg kg−1, respectively, whilst cadaverine, spermidine and spermine were the major BAs in hepatopancreas, reaching 283.45 ± 3.95 mg kg−1, 62.87 ± 9.02 mg kg−1 and 155.31 ± 4.55 mg kg−1, respectively, after postmortem storage at 25 °C for 12 h. With time increasing, Acinetobacter, Flavobacterium, Aeromonas and Chryseobacterium at 25 °C and Acinetobacter, Flavobacterium, Psychrobacter at 4 °C in tail meat as well as Bacteroides and Muribaculaceae at 25 °C, and Acinetobacter, Psychrobacter at 4 °C in hepatopancreas, gradually became the major genus at the end of storage. Based on the results of spoilage microorganisms and biogenic amines, crayfish stored at 4 °C and 25 °C could be edible within 24 h and 6 h, respectively. [ABSTRACT FROM AUTHOR]

Summary: Inventions into chitosan oligosaccharide (COS) derivatives over recent decades have hugely broadened their application in food safety. Herein, monomethyl fumaric acid (MFA) was grafted on the OH position of COS to synthesise new COS‐O‐MFA derivatives and evaluated their in vitro antibacterial properties. The degrees of substitution (DS) of the derivatives yielded almost 15% with the range of 0.093 to 0.260. The in vitro antibacterial properties of the new COS‐O‐MFA1‐3 derivatives against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) were significantly enhanced concerning COS. Based on the finding, the introduction of MFA and increasing DS have a great impact on the enhancement of antibacterial properties of the COS‐O‐MFA1‐3 derivatives. This work proves that COS‐O‐MFA1‐3 derivatives can be potential novel antibacterial agents and also open up a new avenue to improve their antibacterial attributes. [ABSTRACT FROM AUTHOR]

Taking the spices in cooked flavor craytish as the research object, the angle of repose, the slip angle, the swelling capacity and the dissolution effect of different particle size were studied after micro-grinding and screening. In addition, the color, sensory, volatile flavor components and adding amount of the boiled liquid of the spices were compared and analyzed. The results showed that with the decrease of particle size, the angle of repose and the slip angle of the material increased gradually, while the swelling capacity decreased gradually. Spices of 820~1500 μm could achieve the highest spice dissolution effect and the most intense aroma. Compared with the original size of spices, relative content of volatile flavor compounds in 820 μm spices was higher. The 820 μm spices was the most suitable for cooking the soup of cooked flavor craytish and its additive amount was 3~4 g/ L. [ABSTRACT FROM AUTHOR]

BACKGROUND Texture softening is always a problem during chilling of grass carp fillets. To solve this problem and provide for better quality of flesh, understanding the mechanism of softening is necessary. Gelatinolytic proteinases are suspected to play an essential role in the disintegration of collagen in softening of fish flesh. In the present study, the types and contribution of gelatinolytic proteinases in chilled fillets were investigated. RESULTS: Four active bands (G1, 250 kDa; G2, 68 kDa; G3, 66 kDa; G4, 29 kDa) of gelatinolytic proteinases were identified in grass carp fillets by gelatin zymography. The effect of inhibitors and metal ions revealed that G1 was possibly a serine proteinase, G2 and G3 were calcium‐dependent metalloproteinases and G4 was a cysteine proteinase. The effect of the inhibitors phenylmethanesulfonyl fluoride (PMSF), l‐3‐carboxy‐trans‐2,3‐epoxy‐propionyl‐l‐leucine‐4‐guanidinobutylamide (E‐64) and 1,10‐phenanthroline (Phen) on chilled fillets revealed that gelatinolytic proteinase activities were significantly suppressed. Collagen solubility indicated that metalloproteinase and serine proteinase played critical roles in collagen breakdown during the first 3 days, and cysteine proteinase revealed its effect after 3 days. Meanwhile, during chilled storage for 11 days, the final values of shear force increased 19.68% and 24.33% in PMSF and E‐64 treatments when compared to control fillets respectively, whereas the increase after Phen treatment was 49.89%. CONCLUSION: Our study concluded that the disintegration of collagen in post‐mortem softening of grass carp fillets was mainly mediated by metalloproteinase and to a lesser extent by serine proteinase and cysteine proteinase. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

This research evaluates the quality and acceptability of 25%, 50%, and 75% fish protein concentrate (FPC) egg substituted cakes. Proximate chemical composition, batter and cake physical quality, microbial activity, and sensory evaluation were carried out. An impressive increase in protein, fats and ash content was noticed in GPSC. By increasing the FPC concentration, the viscosity of batters and cake volume decreased, while the specific gravity increased. In texture, the hardness, chewiness, and gumminess were increased while elasticity and cohesiveness were decreased with increase in substitution. An increase in substitution increased baking loss (BL) but reduced the water activity (aw) and the number and size of air bubbles in cake batter. By evaluating microbial activity, the total plate count (TPC) value increased, and the total fungal count (TFC) decreased while the cake crumb showed inconsistent change. The cake with 75% egg substitution was highly nutritious but displayed lower sensory attributes due to slight fishy flavor and dark color, while 25% and 50% GPSCs showed almost similar sensory attributes but nutritional value of 50% GPSC was higher than 25% GPSC. So, the cake with 50% substitution is a better option to prepare a good quality protein-enriched cake with acceptable sensory attributes. [ABSTRACT FROM AUTHOR]

β-Carotene (vitamin A precursor) and α-tocopherol, the utmost energetic form of vitamin E (VE), are known to be fat-soluble vitamins (FSVs) and essential nutrients needed to enhance the growth and metabolic functions of the human body. Their deficiencies are linked to numerous chronic disorders. Loading of FSVs within nanoemulsions could increase their oxidative stability and solubility. In this research, VE and β-Carotene (BC) were successfully co-entrapped within oil-in-water nanoemulsions of carrier oils, including tuna fish oil (TFO) and medium-chain triglycerides (MCTs), stabilized by modified starch and Tween-80. These nanoemulsions and free carrier oils loaded with vitamins were stored for over one month to investigate the impact of storage circumstances on their physiochemical characteristics. Entrapped bioactive compounds inside the nanoemulsions and bare oil systems showed a diverse behavior in terms of oxidation. A more deficiency of FSVs was found at higher temperatures that were more noticeable in the case of BC. VE behaved like an antioxidant to protect BC in MCT-based nanoemulsions, whereas it could not protect BC perfectly inside the TFO-loaded nanoemulsions. However, cinnamaldehyde (CIN) loading significantly enhanced the oxidative stability and FSVs retention in each nanoemulsion. Purity gum ultra (PGU)-based nanoemulsions comprising FSVs and CIN presented a greater BC retention (42.3%) and VE retention (90.1%) over one-month storage at 40 °C than Twee 80. The superior stability of PGU is accredited to the OSA-MS capabilities to produce denser interfacial coatings that can protect the entrapped compounds from the aqueous phase. This study delivers valuable evidence about the simultaneous loading of lipophilic bioactive compounds to enrich functional foods. [ABSTRACT FROM AUTHOR]

Summary: Effects of refrigerated (3.5 ± 0.5 °C), iced (0 ± 0.5 °C) and superchilled (−3.0 ± 1.0 °C) storage on quality of crayfish (Procambarus clarkii) were evaluated by monitoring the water migration, microbial contamination, biogenic amines accumulation, and nucleotides catabolism during 21 days. The results indicated that superchilling was effective in accelerating the rate of water migration and reducing total volatile basic nitrogen, trimethylamine, total viable bacteria, Enterobacteriaceae and psychrotrophic bacteria of crayfish. Meanwhile, significant (P < 0.05) lower putrescine, cadaverine and tyramine contents were observed in superchilled sample (SS), whereas histamine concentrations were at lower levels (0.76–2.31 μmol g−1) in all treatments. In addition, the predominant nucleotides degradation pathway in crayfish was the conversion of inosine monophosphate, which was accumulated massively (3.74 µmol g−1) in SS at the end of storage. According to the dynamic changes of inosine and hypoxanthine contents, the shelf life of SS was prolonged to 15 days. [ABSTRACT FROM AUTHOR]

Summary: The microbial dynamics, diversity and succession characterisation during the fermentation of fish‐chili paste, with and without starter cultures by high‐throughput sequencing, were investigated to identify the relationship between microbial composition and the accumulation of biogenic amines. Results showed that Firmicutes was the predominant phylum, and Lactobacillus and Weissella were the main genera during fermentation process, regardless of the inclusion of starter cultures. Compared with naturally fermented samples (NS; no starter cultures), Pediococcus and Staphylococcus flourished in samples inoculated with SBM‐52 starter culture (Staphylococcus xylosus + Staphylococcus carnosus + Pediococcus pentosaceus + Pediococcus acidilactici). Staphylococcus also accounted for a larger proportion in samples inoculated with WBX‐43 starter culture (Staphylococcus xylosus + Staphylococcus carnosus). Furthermore, Enterobacter was inhibited in inoculated samples. Unweighted pair‐group method with arithmetic means and principal component analyses revealed that microbiota structures were different among NS, SBM and WBX samples. In case of biogenic amines, the concentration of putrescine, cadaverine and tyramine increased to higher levels in NS samples compared with inoculated samples. Our work also investigated the relationship between core bacterial communities and biogenic amines. This study provided an improved understanding for the effects of starter cultures on the microbial community and the quality of fish‐chili paste. [ABSTRACT FROM AUTHOR]

Summary: Effects of endogenous enzymes on texture deterioration of Macrobrachium rosenbergii during frozen storage (−18 °C) were investigated. The prawn was pretreated with iodoacetic acid (IAA) solution to inhibit cysteine proteases and/or phenylmethylsulfonyl fluoride (PMSF) solution to inhibit trypsin before frozen storage, and sterile distilled water was used as the control. After 16 weeks of cryopreservation, the shear force of the groups treated with enzyme inhibitors was significantly higher than that of sterile distilled water‐treated group (control; P < 0.05), while significantly fewer TCA‐dissolved peptides, α‐amino nitrogen and Myofibril fragmentation index (MFI) value were observed in all inhibitor‐treated groups (P < 0.05). Compared with PMSF treatment, IAA or IAA + PMSF treatment effectively alleviated softening and remarkably reduced the accumulation of TCA‐soluble peptides and AAN (α‐amino nitrogen) during frozen storage, with a lower MFI value and a higher sodium dodecyl sulphate‐polyacrylamide gel electrophoresis band intensity. Therefore, endogenous cysteine proteases in muscle play a crucial part in texture deterioration of giant freshwater prawn during cryopreservation. [ABSTRACT FROM AUTHOR]

Summary: The effect of immersion treatment with different concentration (0, 1.0, 5.0, 20.0 and 100.0 mm) of hydrogen peroxide (H2O2) on volatile profiles and gel properties of silver carp surimi gel were investigated. The results showed that the immersion treatment with H2O2 obviously changed flavour characteristic of surimi gel depending on H2O2 concentration and different layers (outside, middle and inner). The contents of typical fishy off‐flavour substances such as 1‐octen‐3‐ol, heptanal, nonanal, octanal and decanal were largely reduced in the outside layer of surimi gel after H2O2 treatment, with no obvious change in the inner portion. The gel strength and whiteness were increased after H2O2 treatment with concentration higher than 20 mm. The content of carbonyl compounds was positively correlated with the concentration of H2O2, suggesting that the volatiles variation of surimi gel probably be highly related to the protein oxidation. In conclusion, immersion treatment with H2O2 provided a promising method to remove fishy odour of surimi gel with improved gel properties. [ABSTRACT FROM AUTHOR]

Summary: This study aimed to determine the role of intramuscular connective tissue (IMCT) in softening of ice‐stored grass carp (Ctenopharyngodon idella) fillet. The change in important proteins in IMCT and impact of IMCT destruction in fish softening were both investigated. The exogenous collagenase was used to differentiate the role of IMCT. Results showed that decorin, elastin and collagen in IMCT decreased by 71%, 48% and 54%, respectively. Decorin and elastin were mainly degraded in the primary stage, while collagen decreased mainly in the later stage. Then, IMCT destruction experiment showed that collagenase was quite effective for destruction of IMCT, while myofibre tissue was not affected. Subsequently, specific role of IMCT could be distinguished. Decrease in shear force became twofold faster in the collagenase group at the beginning than that in the control group, indicating a quite important role of IMCT in maintaining fish texture, especially in the primary stage of storage. [ABSTRACT FROM AUTHOR]

A novel charge‐reversible surfactant, (CH3)2N‐(CH2)10COONa, was designed and synthesized, which together with silica nanoparticles can stabilize a smart n‐octane‐in‐water emulsion responsive to pH. At high pH (9.3) the surfactant is anionic carboxylate, which together with the negatively charged silica nanoparticles co‐stabilize flowable oil‐in‐dispersion emulsions, whereas at low pH (4.1) it is turned to cationic form by forming amine salt which can hydrophobize in situ the negatively charged silica nanoparticles to stabilize viscous oil‐in‐water (O/W) Pickering emulsions. At neutral pH (7.5), however, this surfactant is converted to zwitterionic form, which only weakly hydrophobises the silica particles to stabilize O/W Pickering emulsions of large droplet size. Moreover, demulsification can be achieved rapidly triggered by pH. With this strategy particles can be controlled either dispersed in water or adsorbed at the oil‐water interface endowing emulsions with the capacity for intelligent and precise control of stability as well as viscosity and droplet size. [ABSTRACT FROM AUTHOR]

A novel charge‐reversible surfactant, (CH3)2N‐(CH2)10COONa, was designed and synthesized, which together with silica nanoparticles can stabilize a smart n‐octane‐in‐water emulsion responsive to pH. At high pH (9.3) the surfactant is anionic carboxylate, which together with the negatively charged silica nanoparticles co‐stabilize flowable oil‐in‐dispersion emulsions, whereas at low pH (4.1) it is turned to cationic form by forming amine salt which can hydrophobize in situ the negatively charged silica nanoparticles to stabilize viscous oil‐in‐water (O/W) Pickering emulsions. At neutral pH (7.5), however, this surfactant is converted to zwitterionic form, which only weakly hydrophobises the silica particles to stabilize O/W Pickering emulsions of large droplet size. Moreover, demulsification can be achieved rapidly triggered by pH. With this strategy particles can be controlled either dispersed in water or adsorbed at the oil‐water interface endowing emulsions with the capacity for intelligent and precise control of stability as well as viscosity and droplet size. [ABSTRACT FROM AUTHOR]

Summary: The aim of the present study was to investigate the underlying mechanisms of softening texture in chilled grass carp filletsunderpinning collagen solubility, gelatinolytic proteinase activity and physicochemical parameters. Acid‐soluble collagen (ASC) and heat soluble collagen (HSC) increased markedly, while a significant decline was detected in total collagen and insoluble collagen (ISC) during the first 3 days of storage, coinciding with a loss of shear force and water‐holding capacity (WHC) (P < 0.05). Moreover, the activity of gelatinolytic proteinases was gradually activated and reached the peak at day 3 (P < 0.05). Pearson coefficient analysis showed that gelatinolytic proteinase activity revealed a significant correlation with collagen solubility. Total collagen, ASC, ISC and HSC were significantly correlated with shear force and WHC. Our study clarified that the increase of collagen solubility by gelatinolytic proteinases played an important role for texture softening in the early stage of chilled grass carp fillets. [ABSTRACT FROM AUTHOR]

Fermentation is an important way to process and preserve fish. It not only gives the product a unique flavor and texture, but it also contributes to increased nutritional value and better functional properties. The production of fermented fish relies on naturally occurring enzymes (in the muscle or the intestinal tract) as well as microbial metabolic activity. This review focuses on the role of microorganisms on texture change, flavor formation, and biogenic amines accumulation in fermented fish. In addition, the production conditions and the major biochemical changes in fermented fish products are also introduced to help understand the factors influencing the quality of fermented fish. Moreover, prospects for further research of fermented fish are discussed. [ABSTRACT FROM AUTHOR]

Summary: To evaluate the effects of irradiation and thermal treatments on the quality characteristics of the vacuum‐packaged low‐salted fermented fish (Suanyu) during 90‐day storage, thermal‐treated group (TTG), irradiated‐treated group (ITG) and non‐treated group (CG) were prepared. The results showed that total viable counts reduced by 4.49 and 4.67 log CFU/g after thermal and irradiation treatments, respectively, and no coliforms and pseudomonas growth occurred during storage. Compared with CG, lower levels in L*, springiness, chewiness of TTG and higher levels in L*, b* and chewiness of ITG were detected after 90‐day storage. Total biogenic amines content was significantly reduced in ITG compared with CG and TTG (P < 0.05). Both irradiation and thermal treatments have the potential to maintain quality of Suanyu during room storage. Compared with irradiation, thermal treatment could better stabilise the free amino acids and volatile compounds of Suanyu during room storage, but had some negative effects on texture quality. [ABSTRACT FROM AUTHOR]

Battered and breaded fish nuggets (BBFNs) were fried at three different temperatures (160, 170, and 180°C) for 30–180 s to study the mass transfer kinetics of moisture loss and fat absorption. The mass transfer mechanism was investigated through an analysis of microstructure, surface oil (SO), and penetrated surface oil (PSO) contents of fried BBFNs. The results showed that Fick's second law of diffusion and the first-order kinetic model could well describe the kinetics of moisture loss and fat absorption of the crust, respectively. Transfer coefficients of the two mass transports significantly increased with an increase in the frying temperature (P < 0.05). With the increase in the frying temperature, pore size of the crust increased. The PSO content of the crust also increased with elevated frying temperature. These results suggest that frying temperature affects the moisture loss and fat absorption kinetics of the crust by changing its microstructure. [ABSTRACT FROM AUTHOR]

In order to clarify the action of a seasoning mixture of salt and Chinese liquor in maintaining the hygienic and quality characteristics of refrigerated grass carp, the changes in physicochemical properties, biogenic amines, and microbial growth in grass carp fillets during storage at 4°C for 30 days were investigated. Results showed that fillets lightly salted with Chinese liquor had lower values of total volatile basic nitrogen, drip loss, biogenic amines contents, and higher hardness as well as stable pH during storage, compared to the untreated or individual salted groups. The increase in total viable counts and total psychrophile counts were significantly inhibited by combined adding salt and Chinese liquor. Additionally, Illumina sequencing analysis showed Enterobacteriaceae and Carnobacteriaceae were the major spoilage bacteria species in untreated samples at the end of storage, but they were highly inhibited by adding salt and Chinese liquor. Practical applications: Refrigerated storage can better maintain the fresh quality of fish because it is stored under nonfrozen conditions, but the shelf life is limited due to the action of microorganisms and endogenous enzymes. Food seasoning ingredients have the characteristics of high safety, low cost, and convenient application. The combination of salt with other ingredients in fish curing to develop low‐salt preservation techniques has attached increasing interest. The present study showed that curing of grass carp using salt combined with Chinese liquor can largely delay chemical changes, lower the accumulation of putrescine and cadaverine, and inhibit the growth of spoilage microorganisms in refrigerated fish fillets compared to the untreated group. This study provided a promising cost‐efficient and simple preservation technique of fish. [ABSTRACT FROM AUTHOR]