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Abstract: To improve the characteristics and functionality, and increase the use of fish muscle, three groups mixed starter cultures (group one: Lactobacillus plantarum-15, Staphylococcus xylosus-12 and Pediococcus pentosaceus-ATCC33316 [S-PXP]; group two: Lactobacillus planatrum-15, Staphylococcus xylosus-12 and Lactobacillus casei subs casei-1.001 [S-PXC]; and group three: Staphylococcus xylosus-12, Lactobacillus casei subsp. casei-1.001 and P. pentosaceus-ATCC33316 [S-XCP]) were inoculated in minced silver carp muscle to produce a fermented fish product. During the 48h fermentation at 30°C, silver carp muscle inoculated with mixed starter cultures resulted in a rapid pH decrease, suppression in the increase of thiobarturic acid (TBARS) values, total volatile base nitrogen (TVB-N), trimethylamine (TMA), and the growth of spoilage bacteria and pathogens, and had higher whiteness than the control (without any starter) (P<0.05). The changes in SDS-PAGE indicated extensive hydrolysis of muscle protein occurred during fermentation. This study showed that the mixed starter cultures could substantially improve the flavor, digestibility, and nutritional value of the silver carp muscle. [Copyright &y& Elsevier]

Abstract: The selected 11 chitosan samples were evaluated for their fat- and bile acid-binding capacities, physico-chemical properties, and the correlations between each binding capacity and individual physico-chemical properties. The bile acid- and fat-binding capacities were estimated using in vitro assays, whereas the measured physico-chemical properties were deacetylation degree, swelling capacity, and solution viscosity. Chitosan samples might differ in their binding capacities against fat and/or individual bile acids. The bile acid-binding capacities were 0.20–0.61, 0.43–1.63, and 0.61–1.61μmol/g chitosan for cholic, deoxycholic, and chenodeoxycholic acids, respectively. Stronger binding capacity of chitosan against a selected bile acid does not warrant greater binding capacity for other bile acid. The fat-binding capacity ranged from 1077–1239g oil/g for the chitosan samples under the experimental conditions. No correlation was observed between any binding ability and individual physico-chemical properties, although the swelling capacity of chitosan was correlated to the solution viscosity (, ) and deacetylation degree (, ), indicating that none of the measured physico-chemical properties can be used to predict the fat- or bile acid-binding ability of chitosan. [Copyright &y& Elsevier]

Abstract To better understand the role of fermentative microorganisms in lipid changes during the processing of fermented fish, sterile fish paste with or without the antioxidant tert-butylhydroquinone (TBHQ) was used to investigate the roles of three strains isolated from traditional fermented fish in free fatty acid (FFA) liberation and lipid oxidation. The results showed that the addition of 0.03% TBHQ had no significant influence (P > 0.05) on the strain growth but could effectively inhibit fatty acid oxidation. Staphylococcus xylosus 135 demonstrated the highest liberation of FFAs, followed by Saccharomyces cerevisiae 31, with its released FFAs being almost all polyunsaturated fatty acids (PUFA). Furthermore, the highest amount of PUFA oxidation in FFAs was observed in the samples inoculated with Staphylococcus xylosus 135 (802 mg/kg DM), followed by Lactobacillus plantarum 120 (476 mg/kg DM) and Saccharomyces cerevisiae 31(388 mg/kg DM). The results suggested that Staphylococcus xylosus may play a major role in the lipolysis and lipid oxidation during the processing of fermented fish. Lactobacillus plantarum also contributed to the fatty acid oxidation although it had no obvious lipolysis ability. Highlights • Role of microbes in free fatty acids release and oxidation was determined. • 0.03% TBHQ had no effect on strain growth but inhibit fatty acids oxidation. • Oxidation caused the major loss of fatty acids during fermentation of fish. • Staphylococcus xylosus 135 had the highest ability of lipolysis and lipid oxidation. • Lactobacillus plantarum 120 contributed to lipid oxidation but had no lipolytic activity. [ABSTRACT FROM AUTHOR]

Abstract Effects of processing stage and inoculation of autochthonous starter cultures on the lipid fraction and fatty acid profile in low-salt fermented fish were investigated. Drying had less influence on lipid composition. After 4 weeks of fermentation, there were slight changes in neutral lipid (NL) contents, while the proportion of phospholipids (PL) decreased significantly with a concomitant increase in free fatty acids (FFA). Comparing with the CO batch, addition of starter cultures resulted in increase in FFA contents to different extents, and the sample with Staphylococcus xylosus 135 had the highest FFA contents. Inoculation with Saccharomyces cerevisiae 31 caused minimum PL loss. Fatty acid profile analysis showed that higher proportions of monounsaturated fatty acids and polyunsaturated fatty acids were liberated than saturated fatty acids after fermentation regardless of starter cultures. Addition of starter cultures could retard the loss of the polyunsaturated fatty acids (PUFA) during fermentation. Furthermore, results indicated that the increased FFA especially free PUFA in fermented Suan yu mainly resulted from lipolysis of PL. Highlights • Effects of processing stage and starter cultures on lipid changes were studied. • Fatty acid profile of different lipid classes in fermented fish was determined. • Inoculation of starter cultures could promote lipolysis of Suan yu. • Lipolysis of phospholipids contributed largely to the release of free fatty acids. [ABSTRACT FROM AUTHOR]

Abstract: The physicochemical and rheological properties of silver carp mince with different levels of glucono-δ-lactone (GDL) with or without heat treatment at 90 °C for 20 min were investigated. Breaking force, deformation, and whiteness of GDL-induced gels increased with increasing GDL concentration. Heat treatment of GDL-induced gels led to a significant increase in breaking force and whiteness, but decreased deformation. Disulphide bond formation was observed in GDL-induced gels, which increased after heating of the acidified gels. Solubility profiles of gels in different solutions suggested that gel networks were mainly due to hydrophobic interactions, although other chemical interactions may also occur. SDS-PAGE showed that acidification resulted in a large decrease in myosin heavy chain (MHC) band intensity, suggesting the extensive formation of covalent cross-links among silver carp myosins during GDL-induced gelation. [Copyright &y& Elsevier]

Novel yeasts have been developed in recent years to help reinforce and improve food aroma. This study aimed to investigate the possibilities for aroma improvement using two non- Saccharomyces strains with strong aroma production in sour fish fermentation. Two yeasts, Wickerhamomyces anomalus (Wa) and Pichia fermentans (Pf), screened by growth and environmental tolerance, were used to replace Saccharomyces cerevisiae in the mixed starter for sour fish fermentation. Gas chromatography-mass spectrometry, gas chromatography-ion mobility spectrometry and electronic nose were used to analyze the aroma of sour fish inoculated with different starter cultures. Moisture, pH, colony numbers, and content of free amino acids, organic acids and free fatty acids were monitored during the fermentation. Compared with the Sc group, the Wa group and Pf group had no significant effect on microbial composition, moisture content and free amino acids (P > 0.05) at the end of fermentation, while the Pf group had higher levels of organic acids, free fatty acids and alcohol acyltransferases (P < 0.05). Sensory evaluation revealed that the aroma of the Wa group was more similar to that of the Sc group, with a strong flowery and fruity aroma. Generally, W. anomalus was found to be capable of boosting the blossom-like aroma of sour fish. • Two non- Saccharomyces strains were tested for sour fish fermentation. • Wickerhamomyces anomalus and Pichia fermentans drastically increased esters content. • Inoculation of P. fermentans enhanced the sauce aroma of sour fish. • Inoculation of W. anomalus improved the floral and fruity aroma of sour fish. [ABSTRACT FROM AUTHOR]

In this study, the effect of different temperatures (4 °C and 10 °C) on the physicochemical properties of surimi sol was investigated during various storage time (0–7 d). In addition, the water distribution, gel properties and microstructure of gels prepared from treated surimi sol, both with and without shearing, were analyzed. The results showed a continuous increase in the gel strength of surimi sol, indicating a sol-gel transition occurred. Notably, there was a significant decrease (P < 0.05) in protein solubility and the formation of sol network structures, suggesting protein cross-linking and aggregation after cold storage. The analysis of chemical bonds content and gel electrophoresis pointed to the involvement of disulfide bonds and hydrophobic interactions in protein cross-linking. Furthermore, the cold-induced sol-gel transition adversely affected the quality of heat-induced gel, and this deterioration was exacerbated by shearing before cooking. Compared to the unsheared group, shearing before heating resulted in a more pronounced texture and cooking loss in the sheared group, with the heat-induced gel exhibiting a more disordered and rougher surface. These findings shed light on the importance of controlling the cold storage process and shearing treatment to maintain the desired quality of heat-induced gel in surimi sol applications. [Display omitted] • Protein cross-linking and aggregation occurred obviously during cold storage of surimi sol. • Disulfide bonds and hydrophobic interactions were the main forces involved in cold-gelation of surimi sol. • Cold-gelation of surimi sol caused quality deterioration of heat-induced gel. • Shearing before heating exacerbated quality deterioration of heat-induced gel. [ABSTRACT FROM AUTHOR]

Valorization of Nile tilapia fish head hydrolysate (FHH) for a novel fish sauce fermented by non-halophilic lactic acid bacteria (LAB) in the absence of added salt was investigated. Lactobacillus fermentum PCC (LF-PCC), Lactobacillus plantarum 299v (LP-299v) and Lactococcus lactis subsp. cermoris 20069 (LL-20069) were selected. All the LAB presented good growth in FHH, but LF-PCC had better survival relative to LP-299v and LL-20069. No significant differences in glucose consumption were observed among the three LAB fermented FHH (P > 0.05), while there were significant differences in organic acids especially for lactic acid and acetic acid (P < 0.05). In addition, significantly higher levels of free amino acids were observed in LF-PCC and LP-299v (P < 0.05) fermented FHH. Furthermore, the sample inoculated with LF-PCC yielded the highest level of volatiles, including aroma compounds such as alcohols and esters, without the undesirable odor note that is typical of traditional fish sauce. On the whole, the LF-PCC exhibited better survival and fermentation performance than LL-20069 in the salt-free environment. This study demonstrated that non-halophilic LAB could be applied to the production of a novel fish sauce with a clean flavor. • Nile tilapia fish head hydrolysate were used for a salt-free fish sauce production. • Selected non-halophilic LAB was employed as single starter culture. • All the LAB presented good growth in fish head hydrolysate. • Higher levels of FAAs and volatiles were observed in Lactobacillus fermentum PCC. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effects of l -arginine (L-Arg) on the gel properties of reduced-salt shrimp surimi gel (SSG) treated with microbial transglutaminase (MTGase). The results showed that replacing NaCl with different concentrations of L-Arg in reduced-salt (0.5% NaCl) shrimp surimi treated with MTGase significantly increased the gel strength and texture of SSG, even at low L-Arg (0.5%) concentrations. However, 0.5% L-Arg added alone under low-salt conditions did not significantly improve the gel strength of SGG compared with the control SSG containing 0.5% NaCl. L-Arg and MTGase added together significantly increased the disulfide bonds and protein β-sheet structure of SSG while improving the moisture distribution and rheological properties. The electrophoretic analysis and microstructure images revealed that L-Arg and MTGase together promoted the cross-linking of proteins in shrimp surimi to form a dense gel network structure. In conclusion, the combined treatment of L-Arg and MTGase significantly improved the gel properties of SSG and reduced the amount of NaCl. Therefore, the combined treatment of L-Arg and MTGase could enhance the quality of reduced-salt shrimp surimi products. • L-Arg inhibited protein degradation in shrimp surimi during thermal gelation. • L-Arg could be added to shrimp surimi instead of NaCl to make the shrimp surimi gel (SSG) have better gel quality. • The addition of MTGase significantly improved the gel properties and texture of SSG. • L-Arg and MTGase had a synergistic effect on the quality improvement of SSG. • L-Arg and MTGase affected the rheological properties of shrimp surimi and the chemical interactions of SSG. [ABSTRACT FROM AUTHOR]

The reduction of fat absorption during deep-fat frying of battered and breaded fish balls (BBFBs) was investigated using bamboo shoot dietary fiber (BSDF). BBFBs were prepared with 0–10% BSDF treatments, fried at 170 °C (50 s) followed by 190 °C (10 s), then evaluated for fat absorption, textural characteristics, and other quality parameters. The addition of 6% BSDF in the batter improved sensory quality of fried BBFBs (higher brightness and a golden-yellow crust); fat content of the crust and the core of fried BBFBs decreased from 25.5% and 2.4% to 17.7% and 1.3%, respectively. Hardness and chewiness of the crust and the core of fried BBFBs were also improved after adding BSDF to the batter. Microscopic analysis revealed more a compact crust structure and smaller pores inside the core that were more uniformly distributed when compared to fried BBFBs without BSDF. Moreover, of all the treatments, the addition of 6% BSDF produced the lowest oil penetration into fried BBFBs. These findings proved that BSDF added to the batter can significantly reduce fat absorption allowing low-fat fried BBFBs production. [ABSTRACT FROM AUTHOR]

The effects of different content of sodium chloride (NaCl) and sodium pyrophosphate (SPP) on the stability of myofibrillar proteins (MPs) sol subjected to freeze-thaw cycles (F-T cycles), as well as the performance of heat-induced gel subsequently formed from the frozen-thawed MPs sol, were investigated. The molecular states of MPs with high NaCl (15 g/kg, 25 g/kg) and additional SPP (1 g/kg, 3 g/kg, 5 g/kg) were altered due to the cross-linking and aggregation, showing the larger turbidity, higher surface hydrophobicity, and intrinsic fluorescence intensity. Additionally, compared with the control and 5 g/kg NaCl groups, MPs sol with high NaCl content exhibited less proteins denaturation and higher stability of water molecules after 2 F-T cycles. However, the poor gel properties were observed in high NaCl groups with larger cooking loss, weak gel strength, inferior textural parameters, and disorganized micro-network structure, revealing cross-linking and aggregation of MPs during F-T cycles were negative to the gelling properties. Furthermore, the additional SPP (1 g/kg) significantly inhibited protein aggregation and water migration during F-T cycles of MPs sol, resulting in superior gel properties with ordered gel microstructures. • Freeze-thaw cycles caused structural changes and aggregation of myofibrils. • High NaCl content led to better water stability but inferior gel properties. • Sodium pyrophosphate inhibited aggregation of myofibrillar protein. • Non-disulfide covalent cross-linking was weakened by sodium pyrophosphate. • Moderate sodium pyrophosphate improved gel textural properties. [ABSTRACT FROM AUTHOR]

Softening, causing by the degradation of collagen, leads to serious quality deterioration of fish fillets during post-mortem storage. In order to study the role of endogenous enzymes in softening of fish muscle, collagen fibers from grass carp (Ctenopharyngodon idellus) were degraded by serine proteinase. The structural and biochemical changes of collagen fibers with serine proteinase digestion were investigated in terms of scanning electron microscopy, fourier transform infrared spectroscopy, electrophoresis and chemical analysis. In the present study, an endogenous proteinase (approximately 250 kDa) with gelatinolytic activity was isolated from grass carp muscle by ammonium sulfate precipitation and column chromatographies, and identified as serine proteinase. Collagen fibers were partly disaggregated into collagen fibrils after serine proteinase treatment for 48 h, coinciding with a release of hydroxyproline (5.56 ± 0.02%) and glycosaminoglycans (9.04 ± 0.03%). However, almost all gelatin and 40% of acid-soluble collagen were degraded within 1 h and 6 h, respectively. Meanwhile, serine proteinase-treated collagen fibers maintained the triple-helical structure of collagen molecule, while their thermal stability was gradually decreased with digestion time. All results indicated that disintegration of collage fibers by serine proteinase might be due to both the degradation of proteoglycans and collagen molecules during textural deterioration of chilled grass carp fillets. • Collagen fibers were partly degraded into collagen fibrils by serine proteinase. • Serine proteinase freed hydroxyproline and glycosaminoglycan from collagen fibers. • Collagen fibers were more difficultly degraded than collagen monomer and gelatin. • Serine proteinase involves in textural deterioration of grass carp fillets. [ABSTRACT FROM AUTHOR]

Unique flavor is the key quality of fermented fish. In this study, the precursors and key enzymes related to the flavor of Suanyu were analyzed. The results showed that 17 kinds of free amino acids and 22 kinds of free fatty acids were detected during the fermentation. According to variable importance for predictive components values (VIP), amino acids including aspartate, phenylalanine, methionine, glutamic acid, leucine, valine, isoleucine, cysteine and fatty acids including C16:0, C20:5, C20:4, C18:1, C22:6, C18:0 and C16:1 were screened as key precursors affecting the characteristic flavor of Suanyu. Moreover, the changes of enzyme activities in different metabolic processes of flavor were determined. Phosphofructokinase (PFK), pyruvate kinase (PK), lipoxygenase (LOX), hydroperoxidase lyase (HPL) and alcohol acyltransferase (AAT) activities reached the maximum in the first week of fermentation. However, hexokinase (HK), branched chain amino acid transferase (BCAT), aromatic amino acid transferase (ARAT) and esterase activities significantly decreased with the fermentation. Furthermore, ARAT, HPL, esterase, BCAT, AAT and HK were screened as the key enzymes that affected the characteristic flavor of Suanyu. All these results indicated that the control of key flavor precursors and enzymes during fermentation was a potential method to improve the flavor of fermented fish. • The key precursors and enzymes related to Suanyu flavor were identified using O2PLS-VIP method. • Seven kinds of fatty acids and eight kinds of amino acids were selected as key flavor precursors. • BCAT, HPL and HK enzymes could affect flavor in the early fermentation. • ARAT, esterase and AAT enzymes could affect flavor in the late fermentation. [ABSTRACT FROM AUTHOR]

Fish texture is important for consumers and degradation of myofibrillar structural proteins could cause softening. However, the role of endogenous proteases in degrading was not clear. In this study, protease inhibitors (Ac-DEVD-CHO, E−64 and EDTA-2Na) were used to distinguish the role of endogenous caspase-3, cathepsin B and L, and calpain. Results showed that caspase-3 and calpain had relatively high activity at initial ice-storage and decreased quickly afterwards, while cathepsins increased firstly and then fluctuated. Titin, nebulin and troponin-T were partially degraded by caspase-3 firstly. However subsequently, only titin and troponin-T were affected by cathepsins and calpain. Desmin showed a different degradation pattern. It was influenced by calpain significantly but not by caspase-3. Less than 2.5% of desmin remained after storage. Myofibril fragmentation index and shear force indicated that caspase-3-induced degradation occurred at initial ice-storage, while cathepsins had the greatest importance in texture softening during the whole storage. • Role of endogenous caspase-3, cathepsins and calpain were specified in ice storage. • Caspase-3 initiated degradation of titin, nebulin and troponin-T in fish. • Calpain mainly degraded desmin and desmin remained lower than 2.5% finally. • Cathepsins contributed the most for the fish softening during whole ice storage. [ABSTRACT FROM AUTHOR]

The novel chitosan oligosaccharide derivatives modified with cinnamyl onto the NH 2 position were synthesized through a one-step reaction and their in vitro antibacterial activities were ascertained. The structural characterization and properties of derivatives were verified by UV–vis, FT-IR, 1H, 13C NMR, TGA, XRD, and elemental analysis. The degrees of substitution (DS) of derivatives were from 0.255 to 0.366 with yields up to 82%. The in vitro antibacterial activities for the novel chitosan oligosaccharide derivatives against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were greatly improved compared to COS, sodium benzoate, and potassium sorbate. Moreover, their antibacterial activities were DS-dependent and more sensitive to S. aureus than E. coli. This study demonstrated that the new derivatives were expected to be a promising potential antimicrobial agent in the food industry. • Chitosan oligosaccharide derivatives modified with cinnamyl onto the NH 2 position were synthesized. • The structure of derivatives was identified by FT-IR, NMR, and elemental analysis. • The derivatives showed higher antibacterial activities than chitosan oligosaccharide. [ABSTRACT FROM AUTHOR]

The effects of cold air drying (CD) and hot air drying (HD) on the physical properties and protein stability of slightly salted silver carp fillets were investigated in terms of water-related indicators, texture profile, color and protein denaturation analysis. The results indicated moisture content of fillets exponentially decreased to 1.19 and 1.07 g water/g drying matter at the end of drying, respectively, accompanied with the decreases in water activity, and water mobility based on the results of leftward shifted T 21 and T 22 relaxation time. The gradual increase of hardness and chewiness, and decrease of adhesiveness of dried fillets were observed in both groups during the drying process. By contrast, CD made fillets with higher hardness and chewiness properties when compared to HD under similar moisture content. The more intense browning reaction was observed in hot air dried fillets, reflecting by the sharp increase of b * value (p < 0.05) from the initial 1.25 to final 13.44. Besides, the results of protein-related indicators showed HD easily resulted in protein aggregation and secondary structure degradation. Summarily, this study revealed the change characteristics of salted silver carp fillets during two conventional air dryings, providing a basis to further propose reasonable combination drying programs. • Cold air- (CD) and hot air drying (HD) characteristics of fillets were evaluated. • Higher hardness/chewiness were observed in CD group under same moisture content. • Higher proportion of bound water was observed at the end of HD in samples. • HD easily caused discoloration and protein aggregation denaturation of samples. [ABSTRACT FROM AUTHOR]

The effects of commercial starter cultures on the quality characteristics of fermented fish-chili paste were investigated. Five batches of fish-chili paste were prepared with different starter cultures, namely, SBM-52 (Staphylococcus xylosus, Staphylococcus carnosus, Pediococcus pentosaceus and Pediococcus lactis), PRO-MIX5 (Staphylococcus xylosus, Lactobacillus plantarum and Lactobacillus sakei), WBX-43 (Staphylococcus xylosus and Staphylococcus carnosus) , V3 (Lactobacillus plantarum), and CO (spontaneous fermentation) as the control. The results showed that all the starter cultures accelerated the growth of lactic acid bacteria and obviously reduced the Enterobacteriaceae count compared with the CO batch. SBM-52, PRO-MIX5 and V3 quickly reduced the pH, and there was no obvious difference in the protease activities among these five batches (P > 0.05). The SBM-52 batch displayed a significantly higher level of total free amino acids than the control (P < 0.05). The accumulation of organic acids was mainly due to lactic acid in all the samples. Volatile analysis indicated that more ester compounds were detected in WBX-43 compared with the other samples. E-nose analysis showed an obvious difference in the overall odor among the different samples. In conclusion, the starter cultures of WBX-43 and SBM-52 could be used for the production of high-quality fish-chili paste with better flavor. • Effects of commercial starter cultures on the fish-chili paste were investigated. • Starter cultures benefit microbial quality against the undesirable microorganisms. • An appropriate addition of starter cultures produces more pleasant flavor. [ABSTRACT FROM AUTHOR]

The impact of immersion freezing (IF) with edible solution (ethanol, NaCl, dextran, active protein, chrysin and naringenin) on physical properties of obscure pufferfish (Takifugu Obscurus) was compared with air freezing (AF) and liquid nitrogen freezing (LNF). Freezing process, microstructure, texture characteristics, water holding capacity, and cell integrity were investigated. Results showed that IF(-30 °C) rate was 11.5/4.7-fold quicker than AF(-18/-50 °C) rate. As for microstructure, ice crystals in IF(-30 °C) fish were much smaller than that in AF. Referring to texture characteristics and water holding capacity, shear force and hardness of IF(-30 °C) fish were 12.9% and 16.7% higher, and drip and cooking loss were 44.1% and 8% lower, than that of AF(-50 °C) fish after 24 weeks storage. Besides, IF led to higher integrity of muscle fibers than AF. For all physical indexes, IF fish had similar quality as LNF fish. Principal component analysis (PCA) further proved these results. In conclusion, edible IF(-30 °C) could retard physical properties deterioration of frozen fish in a better way than AF and have potential to replace LNF. • AF, IF and LNF were shown freezing curves and rates. • Microstructure, texture, water holding capacity and cell integrity were compared. • Edible IF(-30 °C) rate was 11.5-fold quicker than AF(-18 °C). • Physical properties and PCA showed edible IF(-30 °C) had similar aspects as LNF. [ABSTRACT FROM AUTHOR]