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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]

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]

The present study was conducted to evaluate the effects of long-term storage at various temperatures (4, 25, and 358C) on flavor and microbiological and physicochemical qualities of traditional Chinese low-salt fermented fish (Suanyu). Food spoilage and pathogenic bacteria (coliforms, Pseudomonas, and Salmonella) were inhibited during the 90 days of storage at all temperatures. Lactic acid bacteria, yeast, and total viable bacteria counts of samples stored at 358C were reduced sharply, whereas other parameters were stable. Compared with refrigerated storage (48C), higher storage temperatures (25 and 358C) accelerated moisture migration, lipid oxidation, and proteolytic degradation. Storage time had a greater effect than storage temperature on the increase of volatile compounds in Suanyu. Refrigerated storage was better than higher storage temperatures (25 and 358C) for maintaining the odor quality of Suanyu during the storage period. Total biogenic amine concentrations in all samples were -200 mg/kg. Suanyu can be consumed safely during 90 days of storage based on the levels of spoilage and pathogenic bacteria and concentrations of biogenic amines, but refrigerated storage effectively slows down the microbial and physicochemical changes, resulting in better organoleptic quality. The results of this study will be useful for processors controlling the safety and quality of fermented fish during transport and storage. [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]

Effects of three carp species on texture, color, and aroma properties of Chinese traditional fermented freshwater fish (Suan yu) were investigated. Suan yu were produced from Ctenopharyngodon idella (Grass Carp, GC), Hypophthalmichthys molitrix (Silver Carp, SC), and Cyprinus carpio (Common Carp, CC) as the control. GC displayed the highest hardness and resilience, while SC showed the lowest texture except for springiness (p <.05). GC had the greatest L* and ΔE* values but the least a* value (p <.05). Esters (7), alcohols (7), acids (9), aldehydes (8), ketones (1), hydrocarbons (4), and others (5) were identified by GC‐MS in all samples. E‐nose analysis showed a remarkable difference in the overall aroma profile among all samples. Sensory evaluation and PCA analysis indicated that grass carp could be used as an alternative raw material for Suan yu production, which would improve the utilization of freshwater fish. Practical applications: Suan yu is a type of Chinese traditional fermented freshwater fish with a unique flavor, which is popular among consumers. Such products are commonly manufactured from fresh common carp (Cyprinus carpio) with long‐term anaerobic fermentation. Grass carp (Ctenopharyngodon idella) and silver carp (Hypophthalmichthys molitrix) are popular among consumers as major domesticated fish in China with higher annual harvests than that of common carp, which show potential as raw materials for Suan yu production. It is the first time to investigate the texture, color, and aroma of Suan yu produced from the three carp species (grass carp, silver carp, and common carp) in the same process and to evaluate their quality differences and acceptability. This will help increase the sources of raw materials for Suan yu production and improve the utilization of freshwater fish. [ABSTRACT FROM AUTHOR]

Fermentation is a traditional food preservation method and is widely used for improving food safety, shelf life, and organoleptic and nutritional attributes. Fermented fish are produced and consumed in different parts of the world and are an integral part of many food cultures. Furthermore, fermented fish are a source of interesting microbes and are an important industry in many countries. This review tries to update the types and manufacturing processes for fermented fish around the world. The emphasis is on this work related to fermented fish and their health benefits, as well as the contribution of microorganisms to their fermentation. A variety of different approaches have been used to determine and understand microbial composition and functionality. Moreover, some challenges and future research directions regarding fermented fish are also discussed in this review. Further research into fermented fish products is of crucial importance not only for the food industry but also for human health. However, extensive in vivo and toxicological studies are essential before the application of bioactive-rich fermented fish products for human health benefits. [ABSTRACT FROM AUTHOR]

Summary: To accelerate fermentation and improve quality of fermented fish, the impact of fermentation at elevated temperature on physicochemical, microbiological and flavour characteristics, as well as biogenic amines (BAs) accumulation of low‐salt fermented fish was investigated. Results showed that increasing temperature at later stage significantly promoted the growth of lactic acid bacteria, retarded the reduction of yeast and increased the titratable acidity, while staphylococci and enterobacteriaceae were inhibited to higher extent when fermented at elevated temperature. BAs contents in samples fermented at 30 °C during later stage were lower than those in the group fermented at 25 °C for 28 days, and the lowest values were observed in the sample initially fermented at 25 °C for 10 days followed by fermentation at 30 °C for 18 days. Furthermore, fermentation at elevated temperature at later stage favoured the formation of desired volatile flavour compounds. Results suggested that fermentation at elevated temperature at later stage could reduce BAs accumulation and enhance quality attributes of low‐salt fermented fish. The impact of fermentation temperature on quality attributes of low‐salt fermented fish. [ABSTRACT FROM AUTHOR]

Summary: In this study, three previously isolated dominant autochthonous strains from Chinese traditional fermented fish products (CTFPs), namely Lactobacillus plantarum 120, Saccharomyces cerevisiae 2018 and Staphylococcus xylosus 135, were used to evaluate their nitrite degradation abilities. The highest nitrite degradation rate (NDR) was observed in L. plantarum 120 (90.70%), followed by S. cerevisiae 2018 (78.75%) and S. xylosus 135 (13.09%). The nitrite reductase activities of L. plantarum 120 and S. cerevisiae 2018 could be promoted by appropriate sodium chloride contents (4%–6%). Meanwhile, nitrite could be degraded in soluble grass carp proteins, and the NDR was positively associated with the protein concentration. Inoculation with L. plantarum 120, S. cerevisiae 2018 and S. xylosus 135 significantly (P < 0.05) decreased the nitrite and nitrate concentrations in CTFPs. Therefore, dominant autochthonous strains, especially L. plantarum 120 and S. cerevisiae 2018, could be used as promising starter cultures to inhibit nitrite accumulation in CTFPs. The nitrite degradation pathways of dominant autochthonous strains isolated from Chinese traditional fermented fish. [ABSTRACT FROM AUTHOR]

The effect of mixed starter cultures isolated from Suanyu on flavor compounds development has been researched. Microorganism, pH, TA, sugars, nonvolatile organic acids and volatile compounds were analyzed in Suanyu with or without starters. In inoculated samples, a higher growth of lactic acid bacteria (LAB) and a declining rate of pH were determined when compared with the controlled samples. Besides, higher levels of volatile compounds were detected in inoculated Suanyu (19342.47, 19852.74 × 106 area units for PS) than those in controlled samples. During the process, aldehydes, acids, alcohols, esters and ketones were formed and increased continuously. Especially in Suanyu with PS, higher levels of ethanol (6973.8, 6549.9 × 106 area units) and acetic acid (2116.8, 2471.1 × 106 area units) were detected, which could produce unique wine flavor and moderate acid taste. Furthermore, high content of hexanal was generated through the addition of PS, which could contribute to a green grass odor. Practical Applications In this study, microorganism, pH, TA, sugars, nonvolatile organic acids and volatile compounds were analyzed in Suanyu with autochthonous starter cultures. The results showed that the generative stability of Suanyu can be assured and the product quality can be advanced by adding autochthonous starter cultures compared with that of noninoculated samples. There is a need to add modern processing technology such as microbial fermentation of the fermentation process to achieve effective control to ensure product flavor and product quality stability. In this study, autochthonous starter cultures isolated from Suanyu, which were propitious to the demand of industrialization. Besides, once the research is applied in the industrialized production, and considerable social and economic benefits can be obtained. Therefore, this study has a good prospect in application. [ABSTRACT FROM AUTHOR]

The hydrolysis of sarcoplasmic proteins during the growth of Lactobacillus plantarum 120 originally isolated from Suanyu, a traditional Chinese low salt fermented fish, was evaluated. Fermentation was carried out in a fish meat model system at 30C for 96 h. Proteolytic activity of this strain on fish muscle sarcoplasmic protein was determined by proteins, peptides and free amino acids analyses. There was a pronounced hydrolysis of almost all protein bands in electrophoretic pattern by L. plantarum 120. It also resulted in the generation of new peptides and disappearance of original peaks. In addition, the studied strain generated greater amounts of free amino acids than the control, especially for alanine, glutamic acid, phenylalanine, valine, methionine, aspartic acid, isoleucine and leucine. In general, proteolysis of fish sarcoplasmic proteins by L. plantarum 120 occurred during fermentation, resulting in increase in peptides and free amino acids, which may contribute to the taste and aroma of Suanyu. Practical Applications Suanyu is one of the Chinese traditional fermented fish products in South China. According to its characteristic flavor and high nutrition value, Suanyu has been accepted around China in recent year. However, Suanyu is still manufactured on a small scale by spontaneous fermentation. It is difficult to guarantee product quality and increase the efficiency. Lactic acid bacteria is one of the essential agents of the meat fermentation process that contribute to the hygienic and sensory qualities of meat products. Lactobacillus plantarum 120, isolated from Suanyu, exhibited optimal properties as a potential starter in our previous work. Once L. plantarum 120 is used as an industrial starter, it will promote fish muscle proteolysis, shorten the fermentation period and then improve product quality assurance activity. [ABSTRACT FROM AUTHOR]

Proteolytic changes in Suanyu, a traditional fermented fish product of China, were determined during 6 weeks of fermentation. The gradual decrease of pH value andawwas detected, accompanied with an increasing trend detected in trichloroacetic acid–soluble C-1: peptides concentration. Protein composition changed throughout the fermentation. A decrease in sarcoplasmic and myofibrillar protein fractions was accompanied by an increase in the insoluble fraction. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed most bands of sarcoplasmic, myofibrillar, and insoluble proteins lightened or disappeared due to proteolysis or denaturation. New bands emerged especially in insoluble proteins. Fluctuation of molecular weight distribution of the water-soluble nitrogen in Suanyu was found during fermentation. The highest percentage in Suanyu end-products was observed in the fraction of <0.18 kDa, followed by 0.18–0.5 kDa, 66.02 ± 0.38% and 10.79 ± 0.27%, respectively. Free amino acids analysis showed that nearly all amino acids increased, especially for Asp, Glu, Met, Phe, Leu, Val, and Ile. Overall, intense proteolysis in Suanyu brought numerous of small peptides and free amino acids, which contribute to the taste and flavor of Suanyu. [ABSTRACT FROM AUTHOR]

Effect of autochthonous starter cultures on the volatile flavour compounds of Chinese traditional fermented fish was studied. Lactobacillus plantarum 120, Staphylococcus xylosus 135 and Saccharomyces cerevisiae 31, isolated from Suan yu, were selected as starter cultures. Volatiles were extracted by headspace solid-phase microextraction ( SPME) and analysed by gas chromatography-mass spectrometry technology ( GC- MS). Esters and alcohols were the main components of volatiles, accounting for over 50 percentage points in all samples. The highest content of esters (3034.54 μg kg−1) was observed in S1 inoculated with L. plantarum 120, while the highest content of alcohols (2164.53 μg kg−1) and ketones (379.98 μg kg−1) was detected in S3 inoculated with S. cerevisiae 31. The content of acids and aldehydes was lower in inoculated samples. Principal component analysis revealed that the volatile composition was primarily influenced by the nature of the starter cultures. L. plantarum 120 and S. xylosus 135 could accelerate fermentation. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the lipolysis and lipid oxidation of Staphylococcus xylosus 135 and Saccharomyces cerevisiae 31 in Suan yu. Suan yu were made inoculated with and without two strains at different stages, and model systems of emulsions were also established. Lipolysis and lipid oxidation were evaluated by determining the changes in free fatty acid ( FFA) content and composition, conjugated diene ( CD) value and thiobarbituric acid reactive substances ( TBARS) value. The total FFA of the sample without cultures increased from 476.61 mg/100 g fat to 1413.89 mg/100 g fat after 5 weeks fermentation, while those of samples with cultures declined to 258.98 and 452.89 mg/100 g fat, respectively. On the other hand , CD and TBARS values of samples with inoculation markedly increased. In the model system, higher FFA, CD and TBARS values for the samples added with CFE were observed. This study showed that Staphylococcus xylosus 135 and Saccharomyces cerevisiae 31 made a significant contribution to lipolysis and lipid oxidation during the processing of Suan yu. [ABSTRACT FROM AUTHOR]

Abstract: A total of 21 Lactobacillus plantarum were isolated from a Chinese traditional low salt fermented whole fish product “Suan yu” and identified by biochemical and molecular methods. The isolates were screened for acidifying and amino-biogenic ability for proteolysis, lipolysis, antimicrobial activity, and sensory in order to select the most suitable candidates as the starter cultures. All the strains had high acidifying activities and were able to reduce the pH to lower than 4.5 in 36, 24 and 16 h at 15, 25 and 37 °C respectively. Major strains showed antimicrobial activities against Listeria monocytogenes, Staphylococcus aureus and Escherichia coli, and ten L. plantarum strains could produce bacteriocins. Five L. plantarum strains exhibited weak proteolytic activities against myofibrillar proteins, as evidenced by the agar plate assay and sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS-PAGE). None of the strains showed lipolytic activity. Major L. plantarum strains displayed different enzymatic profiles. Besides, the isolates mostly showed negative-decarboxylase activities, but Lp-10 had a decarboxylase activity against l-tyrosine. Furthermore, the fermented fish surimi inoculated with Lp-15 and Lp-21 strains respectively scored high for overall acceptability. Therefore, Lp-15 and Lp-21 presented the best technological properties, which should be given first priority as the starter culture for manufacturing fermented fish products. [Copyright &y& Elsevier]

Abstract: In this study, three groups of mixed starter cultures (S1: Lactobacillus plantarum 120, Staphylococcus xylosus 135 and Saccharomyces cerevisiae 31; S2: L. plantarum 145, S. xylosus 135 and S. cerevisiae 22; S3: Pediococcus pentosaceus 220; S. xylosus 135 and S. cerevisiae 22), isolated from Suan yu, were inoculated to produce the traditional fermented fish. After 42 days fermentation at 24 °C, Suan yu inoculated with different mixed starter cultures underwent rapid growth of lactic acid bacteria (LAB), declined pH, suppressed increase of thiobarbituric acid (TBARS) and total volatile base nitrogen (TVB-N) as well as growth of spoilage bacteria and pathogens. Besides, Suan yu had higher contents of non-protein nitrogen (NPN) and total free amino acids (FAA) compared to the control (P < 0.05). The muscle proteins were severely hydrolyzed during fermentation (SDS-PAGE). Moreover, the sensory evaluation indicates the fermented fish was more widely accepted than the control. The results suggest that the inoculation with S1, S2 and S3 reduced the lag time that fermentation began and improved the quality of Suan yu. [Copyright &y& Elsevier]

In this study, two groups of mixed starter cultures ( S1, S2), which were isolated from Suan yu, were inoculated for this experimental product, and a batch without starters was used as the control. The effect of the mixed starter cultures on the suppression of biogenic amine ( BA) produced during the ripening of Suan yu was investigated. Changes in BA, p H, total volatile base nitrogen ( TVB-N), microbial counts and free amino acids ( FAA) contents were detected during ripening. The results show that the mixed starter cultures rapidly decreased p H, inhibited the growth of contaminant microorganisms emerged in the sample and drastically reduced the accumulations of tyramine, putrescine and cadaverine. However, histamine and spermine were not produced in any batch. Besides, p H, FAA and BA production were not directly correlated. The study suggests that inoculation with S1 and S2 inhibited BA, thereby improving the product safety. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports the first study on the chemical and microbial properties of Suan yu, a sanitary Chinese traditional low-salt fermented whole fish product of high nutrition, unique flavor, and long-storage capability. Six brands of Suan yu from different locations in China were studied. Significant differences were observed in some characteristics of this traditional fermented fish, raw material and other spontaneously fermented fish. The values of Enterobacteria and Pseudomonads were under the detection limits in six different brands. In addition, the products contained higher protein and lower moisture ranging from 17.2% to 22.9% and 52.9%–58.1%, respectively. The pH values ranged between 4.27 and 5.18, and lactic acid was the major organic acid. The proteolysis of the myosin heavy chain and actin chain were observed through sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis. Moreover, low concentrations of biogenic amine (BA) and thiobarturic acid (TBARS) values were found in all samples. The characteristics of the six Suan yu brands were all influenced by raw materials, ingredients, and fermentation processes and conditions. [Copyright &y& Elsevier]

• Aroma of a new fish flavouring was modulated by the cysteine-xylose Maillard reaction. • Response surface methodology assessed the optimum condition of this reaction. • 2-Methyl-3-furanthiol (MFT) and 2-furfurylthiol (FFT) were used as responses. • Heating temperature significantly affected the production of MFT and FFT. Aroma defects limit the application of fish protein hydrolysates as flavourings. This study aimed to develop a flavour concentrate from fermented tilapia fish head hydrolysate by maximising the Maillard reaction production of meaty and roasted aroma associated compounds. We studied the optimal conditions of the Maillard reaction of xylose with cysteine to form meat-like odorants using response surface methodology. A 3-factored and 3-leveled Box Behnken design was employed, where the independent variables were cysteine concentration (A, w/v, %), heating temperature (B, °C) and heating time (C, min). 2-Methyl-3-furanthiol and 2-furfurylthiol were used as response factors. The optimal conditions were obtained as follows: A, 0.80%; B, 183.80 °C; C, 89.34 min. Compared with the controls, Maillard reaction products enriched the meaty and roasted aroma associated compounds in the treated hydrolysate. In conclusion, the treated tilapia fish head hydrolysate may be used as a base in development of new fish-based flavourings. [ABSTRACT FROM AUTHOR]

This study aims to investigate the technological properties of yeast strains isolated from traditional low‐salt fermented Suan yu fish as starter culture. A step‐by‐step approach was used to determine the technological properties of the isolated yeast strains. The enzymatic activity (catalase, urease, β‐glucosidase, protease, and lipase) under adverse conditions (pH, salt, and temperature) were evaluated. Principal component analysis was used to assess data. Twenty‐five strains with desirable technological properties were selected for evaluation of probiotic traits (tolerance at pH 2.5 and 0.3% bile salts, antimicrobial activity, hydrophobic properties, and biofilm production). These isolates were identified by sequencing the D1/D2 region of 26S rDNA. Finally, seven isolates with desirable probiotic traits were analyzed for their ability to survive through gastric transit using a gastrointestinal simulation model. An In vitro test showed that isolates 3, 12, 19, 24, and 43 exhibited high survival levels (60%–70%), similar to those of the indicator strain (Saccharomyces cerevisiae). The results suggest that five isolates (S. cerevisiae strains 3, 12, 19, 24, and 43) showed desirable technological properties and probiotic traits and therefore can be used as functional starter cultures to produce fermented fish products. Practical applications: Researchers have investigated the activity of LAB as functional and probiotic microorganisms; however, information on the probiotic potential of yeasts remains limited. Yeasts are microorganisms that present and induce biochemical changes in several fermented meat and fish products. In the present study, the technological and probiotic properties of 52 isolates from Suan yu were investigated to identify potential probiotic strains for starter cultures. Our results suggest that five isolated S. cerevisiae strains showed desirable technological properties and probiotic traits and therefore can be used as functional starter cultures to produce fermented fish products, and other fermented foods. Functional yeast isolates are used to effectively improve the quality of fermented fish products for consumer acceptance. This study has focused on the possibility to produce a functional Suan yu using a potential probiotic S. cerevisiae as starter culture to enhance health benefits. [ABSTRACT FROM AUTHOR]

The effects of three autochthonous starter cultures (Lactobacillus plantarum 120, Saccharomyces cerevisiae 2018 and Staphylococcus xylosus 135) on biogenic amines (BAs) accumulation in Chinese traditional fermented freshwater fish products (CTFPs) were studied. Some quality parameters of CTFPs, namely microbiological characteristics, α‐amino nitrogen, trichloroacetic acid (TCA)‐soluble peptides, protease activity, and free amino acids (FFAs) were also detected. No histamine accumulation was observed in each fermentation group. Putrescine and tyramine were the dominating BAs in CTFPs. Putrescine accumulation was significantly (p < 0.05) suppressed by inoculated with L. plantarum 120 and S. xylosus 135, and lowest tyramine content (363.15 mg/kg) was observed in sample inoculated with mixed starter cultures. Low levels of cadaverine (8.22–20.03 mg/kg), spermidine (6.60–8.11 mg/kg) and spermine (7.94–9.62 mg/kg) were observed in all groups at the end of the fermentation. Additionally, total BAs contents showed a significant (p < 0.05) correlation with protease activities and α‐amino nitrogen contents. Practical applications: The present study demonstrated the changes in some quality parameters and BAs contents of CTFPs influenced by different starter cultures. Results showed that lactic acid bacteria (LAB) and yeast were gradually increased, severe hydrolysis of proteins was occurred during CTFPs fermentation process, histamine accumulation was inhibited completely in all fermentation groups, putrescine was significantly (p < 0.05) suppressed by inoculated with L. plantarum 120 and S. xylosus 135, and significant (p < 0.05) inhibition of tyramine was observed in sample inoculated with mixed starter culture. To date, CTFPs were usually produced by spontaneous fermentation, and the quality was unsteady. Therefore, to improve the quality and avoid the unacceptable levels of BAs accumulation, inoculation of proper autochthonous starter cultures is advisable. [ABSTRACT FROM AUTHOR]

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]

Phospholipid molecular species composition of Chinese traditional low-salt fermented fish (Suan yu) inoculated with different starter cultures was investigated. Fifty-six molecular species of phospholipid including 20 species of phosphatidylcholine (PC), 15 species of phosphatidylethanolamine (PE), 6 species of phosphatidylserine (PS), 9 species of lysophosphatidylcholine (LPC), and 6 species of lysophosphatidylethanolamine (LPE) were identified using ultra-performance liquid chromatography with quadrupole-time-of-flight mass spectrometry (UPLC-Q-TOF-MS). PC (C16:0–C18:1), PE (C16:0–C22:6), PS (C15:0–C22:6), LPC (C22:6) and LPE (C22:5) were the predominant species. Bioactive polyene phospholipids mainly existed in PE. Furthermore, starter cultures exhibited different influence on phospholipid molecular species. Compared to naturally fermented Suan yu, more molecular species of PE and PS as well as polyene phospholipids were detected in the samples inoculated with Saccharomyces cerevisiae 31 and mixed starter cultures. [ABSTRACT FROM AUTHOR]

• The aroma-profiles of fermented sour fish were characterized. • Eighteen aroma compounds (OAV>1) were confirmed. • Key aroma compounds were identified by recombination and omission experiments. • Key aroma compounds included four esters, two aldehydes and one furan. In this study, key aroma compounds of low-salt fermented sour fish were characterized using headspace solid-phase micro extraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC–MS), odor activity values (OAV) and aroma recombination and omission experiments. Eighty-eight volatile compounds, including esters, aldehydes, alcohols, acids, furans and pyrazines, were identified by HS-SPME-GC–MS. Eighteen aroma-active compounds were quantified by employing calculation of OAV greater than 1. A recombination aroma model prepared using aroma-active compounds based on the odorless fish matrix sensorially matched the aroma of fermented sour fish with a score of 4.5 out of 5. The omission experiment showed that 7 out of 18 compounds had a significant contribution to the overall aroma (P < 0.05). The key aroma compounds of fermented sour fish were concluded to be ethyl acetate (OAV = 189), ethyl hexanoate (OAV = 66), isoamyl acetate (OAV = 424), ethyl butyrate (OAV = 26), hexanal (OAV = 49), 1-hexadecanal (OAV = 14) and 2-pentylfuran (OAV = 13). [ABSTRACT FROM AUTHOR]

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]

The correlation between microbiota succession and flavor development in Chinese traditional fermented fish (Suanyu) inoculated with mixed starter cultures was studied. The results showed that 17 free amino acids, 22 free fatty acids and 9 organic acids were present. A total of 81 aroma compounds were detected during Suanyu fermentation. Aldehydes were the most abundant aroma compounds in the early stage of fermentation and esters contributed most to the aroma in the later stage of fermentation. The correlation analysis of microbial succession and flavor dynamics based on bidirectional orthogonal partial least squares (O2PLS) suggested that in addition to starter cultures, other microorganisms including 2 bacteria genera and 11 fungi genera were also responsible for the formation of flavor compounds. These results may help focus further research to improve the flavor quality of traditional fermented fish. • Correlations between microorganism and flavors was preliminarily explored. • Correlations between flavors and precursors were preliminarily explored. • Five genera were determined as core functional flavor-producing microbiota. • Lactobacillus are involved in the most flavors formation. • The production of ethyl acetate was strongly associated with the fungi genera. [ABSTRACT FROM AUTHOR]

Highlights • Three autochthonous strains isolated from CTFPs could degrade NDMA directly. • LAB counts were obviously promoted by L. plantarum 120 and mixed starter cultures. • The precursors levels of NDMA in inoculated samples were lower than in control. • The accumulation of nitrite and NDMA were inhibited in inoculated samples. Abstract This study investigated the effects of Lactobacillus plantarum 120, Saccharomyces cerevisiae 2018 and Staphylococcus xylosus 135 inoculation on N -nitrosodimethylamine (NDMA) and its precursors formation, and on microbiological characteristics of Chinese traditional fermented fish products (CTFPs). The results indicated that three strains could directly degrade NDMA in culture broth, and the highest degradation rate was observed in L. plantarum 120. The lactic acid bacteria counts in samples inoculated with L. plantarum 120 and mixed starter cultures were significantly (P < 0.05) higher than the others during the initial and middle fermentation stages (≤3 weeks). The final contents of total volatile base nitrogen, trimethylamine, dimethylamine, nitrite and NDMA in inoculated samples were significantly (P < 0.05) lower than those in spontaneous fermentation samples. According to these results, the inoculation with autochthonous starter cultures was a promising method to inhibit the NDMA and its precursors accumulation in CTFPs during fermentation process. [ABSTRACT FROM AUTHOR]

To investigate the contribution of autochthonous microflora on free fatty acids (FFA) release and flavor development in low-salt fermented fish, three groups of processed fish, including bacteriostatic-acidification group (BAG), bacteriostatic group (BG), and spontaneous fermented fish (CG) were established. Results showed that addition of NaN 3 reduced microbial load in BAG and BG below 3.5 log CFU/g after 3 weeks of incubation. Activities of lipases and lipoxygenase declined markedly with increasing time, where BG had the highest activities, followed by CG and BAG. There is a 36.3% higher in the total FFA content in CG than that in BAG, indicating both microbial and endogenous lipases contributed to the FFA liberation in fermented fish while endogenous lipases play a major role. However, compared to BAG and BG, largely higher levels of volatile compounds were observed in CG, suggesting that autochthonous microflora dominated the generation of volatile flavor compounds in fermented fish. [ABSTRACT FROM AUTHOR]

[Display omitted] • The inoculation of mixed starter cultures and addition of spices mixture could effectively inhibit BAs production. • The inoculation of starter cultures could inhibit Enteroccoccus and other microorganisms. • Spices introduced Bacillus into Suanyu. • Staphylococcus , Macrococcus , and Lactobacillus were the core microbial genus in Suanyu. • Fermentation with starter cultures and spices could improve the safety of fermented fish. Suanyu is one of the traditional Chinese fermented fish products with a pleasant flavor. The present study sought to evaluate the effects of starter cultures and spices on the physicochemical properties and microbial flora of Suanyu after fermentation and storage. The results indicated that fermentation with mixed starter cultures could lower the pH and inhibit TVB-N formation in Suanyu after fermentation and during storage. Moreover, inoculation of starter cultures could promote free amino acids production during storage. Additionally, inoculation of mixed starter cultures and spices mixture could effectively inhibit the formation of most biogenic amines in Suanyu, revealing the significant role of mixed starter cultures. Staphylococcus , Macrococcus , and Lactobacillus were the core microbial genus in Suanyu. The inoculation of starter cultures could inhibit Enteroccoccus and other microorganisms, while spices introduced Bacillus into Suanyu. The study results provide a theoretical basis for the industrial production and storage of Suanyu. [ABSTRACT FROM AUTHOR]

[Display omitted] • The whole fermentation of Suanyu was divided into 3 stages using OPLS-DA model. • The aroma markers of different fermentation stage were confirmed. • The characteristic flavor metabolic network of Suanyu was constructed. • The different metabolic roles of key microbes in flavor formation were elucidated. Microbial metabolism is crucial for the flavor development of traditional Suanyu. A total of 21 characteristic volatile compounds of Suanyu were identified according to GC-MS combined with GC-O analysis. HCA results indicated that the whole fermentation process could be divided into three stages: raw material (fresh), initial fermentation (0–2 week) and the late fermentation (2–4 week). Moreover, nine flavor markers in different fermentation stages were revealed using the OPLS-DA model and VIP values. Furthermore, metagenomic sequencing was used to analyze the possible formation pathways of the characteristic flavor compounds and identify the key microorganisms related to flavor formation at the gene level. The top 10 bacterial genera associated with flavor formation were Staphylococcus , Enterococcus , Vibrio , Kocuria , Lactobacillus , Macrococcus , Streptococcus , Enterobacter , Lactococcus and Pediococcus , accounting for large parts of flavor formation of fermented Suanyu. This study is helpful to elucidate the different metabolic roles of microorganisms in flavor formation during fermentation. [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]