Effects of mixed starter cultures and exogenous L-Lys on the physiochemical and sensory properties of rapid-fermented fish paste using longsnout catfish by-products

Enhancing the quality of fermented sufu: synergistic effects of Staphylococcus sciuri and Bacillus toyonensis

BACKGROUND

Sufu, a traditional Chinese fermented soybean product, is renowned for its long history and distinctive taste. Despite its popularity, variability in quality due to conventional fermentation practices has been a persistent challenge. This study aimed to improve the quality of sufu by introducing Staphylococcus sciuri and Bacillus toyonensis, both of which were isolated from traditional Chinese fish sauce and exhibit strong protease activity.

RESULTS

Microbial inoculants accelerated the fermentation process and improved the sufu quality significantly, with the mixed-strain group (MF) showing the greatest improvement. After 15 days of fermentation, the protease activity of the MF group was 2.8 times that of the natural fermentation (NF) group. At 20 days of fermentation, compared with the NF group, the total volatile basic nitrogen (TVB-N) level in the MF group decreased by 33% (P < 0.05). The amino acid nitrogen (AAN) content was 1.47 times higher and the trichloroacetic acid-soluble (TCA-soluble) peptide content was 1.18 times higher (P < 0.05 in both cases). The production of key volatile flavor compounds such as 1-octen-3-ol, 4-methyl-1-pentanol, isoamyl alcohol, methyl palmitate, and 2-pentylfuran in the artificially fermented samples enhanced the overall flavor of the product. The microstructure of the inoculated samples was improved, leading to a better texture and mouthfeel in the final product.

CONCLUSION

Employing artificial inoculation with S. sciuri and B. toyonensis, especially in the MF group, significantly enhanced both the safety and quality of sufu. This study offers a theoretical basis for developing new varieties of sufu. © 2025 Society of Chemical Industry.

Dynamics of bacterial composition and association with quality formation and histamine accumulation during Antarctic krill fish sauce fermentation

In this study, we first verified the feasibility of using Antarctic krill as a raw material for quick-brewed fish sauce, and the results showed that the amino acid nitrogen (AAN)and total soluble nitrogen(TSN) in the fermented 30 days fish sauce met the national level fish sauce standards, but the histamine content exceeded the maximum limit value of histamine in fish sauce (400 mg/kg) set by the International Codex Alimentarius Commission (CAC) and the European Union (EU). On this basis, the correlation between physicochemical indexes and bacterial communities during the fermentation of fish sauce was investigated using high-throughput sequencing, culture method. The correlation analyses revealed the relationship between bacterial communities and the quality and safety of fish sauce, and these studies will be helpful for the development of Antarctic krill fish sauce. The results showed that Staphylococcus were positively correlated with the accumulation of histamine and TVB-N during fermentation. This may be due to the presence of genes encoding histidine decarboxylase in Staphylococcus. Virgibacillus was positively correlated with the accumulation of AAN during fermentation. It was also found that Virgibacillus dokdonensis had a high protease activity (153.22 U/mL) and Staphylococcus epidermidis was the most capable of producing histamine at 31.59 mg/kg. Therefore histamine can be reduced by adding bacteria that inhibit the growth of Staphylococcus or degrade histamine as a fermenter.

Effects of starters on the quality of fermented fish (Zaoyu): Key microorganisms for coloring, softening, and improving flavor

This study aimed to improve the quality of fermented fish Zaoyu by inoculating different starters (Chuzhai starter, Aroma starter and Sweetness starter), and examining the role of key microorganisms. High-throughput sequencing showed the microbial composition of Aroma starter was similar to Sweetness starter, but both were different from Chuzhai starter. Compared to traditional fermentation, inoculated fermentation with Aroma starter and Sweetness starter strengthened the color of Zaoyu by Maillard reaction and softened the muscle by degrading muscle fibers, endomysium and epicardium. Additionally, the taste and odor of Zaoyu were obviously improved, because the proportion of sweet, umami and aroma compounds increased by 2.51 %, 7.09 %, and 22.94 %, respectively. Correlation analysis combined with metabolic functions showed key microorganisms, such as Trichococcus, Rhizopus, Saccharomycopsis, Saccharomyces, etc., improved the quality mainly by promoting sugar production and conversion, and protein degradation. Overall, Aroma starter and Sweetness starter were superior in improving the quality of Zaoyu.

Impact of Enzyme-Microbe Combined Fermentation on the Safety and Quality of Soy Paste Fermented with Grass Carp By-Products

Freshwater fish processing produces 30-70% nutrient-rich by-products, often discarded or undervalued. Grass carp by-products, rich in protein, offer potential as raw materials for fermented seasonings. This study explores the use of these by-products-specifically, minced fish and fish skin-in soybean fermentation to evaluate their effects on the quality of the resulting seasonings. Tetragenococcus halophilus was used as a starter culture alongside food-grade protease to assess their combined impact on the safety and flavor of soy fish paste and soy fish skin paste. The findings revealed that natural fermentation resulted in higher protein hydrolysis in soy fish skin paste compared to soy fish paste. Across all fermentation conditions, amino acid nitrogen levels increased, while total volatile basic nitrogen levels decreased in both pastes, indicating improved quality. Additionally, microbial fermentation significantly reduced biogenic amine content in soy fish paste, enhancing safety. Enzymatic fermentation further enriched the flavor of both pastes by boosting key compounds such as 2-methylbutanal and ethyl acetate. Notably, enzyme-microbe co-fermentation harnessed the strengths of both methods, achieving improved safety and enhanced flavor profiles while elevating overall product quality. These findings suggest a promising way to transform freshwater fish by-products into high-value condiments, advancing sustainable food processing.

Changes in the chemical properties and metabolite profiling of fish sauce prepared from underutilized large yellow croaker roes during fermentation at different temperatures

Fish sauce is a popular aquatic condiment with unique flavor. In this study, the changes in the chemical properties and metabolite profiling of fish sauce from large yellow croaker roes during fermentation at different temperatures were revealed. The results found that the contents of total acid, amino acid nitrogen, total soluble nitrogen and soluble salt-free solids of fish sauce fermented at 40 °C were higher than those in other temperatures groups (25 °C and 32 °C), while the contents of total volatile basic nitrogen were lower than other temperatures. Therefore, 40 °C was the ideal fermentation temperature for fish sauce. The metabolomics analysis showed that organic acids, amino acids, nucleotide, and lipid compounds were found to participate in the biosynthesis pathway. Compared to 25 °C and 32 °C, fermented at 40 °C could increase the abundance of metabolic substances in the fish sauce, such as sugar alcohols, L-Citrulline, L-Aspartic acid, L-Cysteine, Glutathione, and L-Arginine. These results provide a theoretical basis for the production of high-quality fish sauce and the high-value utilization of fish roes.

Suanyu fermentation strains screening, process optimization and the effect of thermal processing methods on its flavor

Suanyu is a famous traditional fermented aquatic food in south China. However, the quality of Suanyu is unstable due to natural fermentation based on the environment. This work screened suitable microbial fermenters (Enterococcus rivorum and Enterococcus lactis) from traditional fermented fish and optimized a suitable fermentation process. Effects of different fermentation (natural and mixed starters fermentation) and thermal treatments (microwave, frying and roasting) on the flavor of Suanyu were investigated. Compared to the natural fermentation group, the TVB-N content (31.5 mg/100 g) was lower, the total acidity (5.12 g/kg) and flavor compounds content were richer in the mixed starters fermentation group (P < 0.05). But there was no significant difference in histamine content (P > 0.05). The roasting treatment group contained higher contents of free amino acids, organic acids, nucleotides and richer key aroma components. The electronic nose was able to distinguish between the differently treated samples. The sensory evaluation result showed that roasted and fried samples had a more acceptable flavor and color. This work will provide a theoretical reference for the standardized production of Suanyu and the development of pre-cooked products.

A Comprehensive Review with Future Insights on the Processing and Safety of Fermented Fish and the Associated Changes

As an easily spoiled source of valuable proteins and lipids, fish is preserved by fermentation in many cultures. Over time, diverse types of products have been produced from fish fermentation aside from whole fish, such as fermented fish paste and sauces. The consumption of fermented fish products has been shown to improve both physical and mental health due to the composition of the products. Fermented fish products can be dried prior to the fermentation process and include various additives to enhance the flavours and aid in fermentation. At the same time, the fermentation process and its conditions play a major role in determining the quality and safety of the product as the compositions change biochemically throughout fermentation. Additionally, the necessity of certain microorganisms and challenges in avoiding harmful microbes are reviewed to further optimise fermentation conditions in the future. Although several advanced technologies have emerged to produce better quality products and easier processes, the diversity of processes, ingredients, and products of fermented fish warrants further study, especially for the sake of the consumers' health and safety. In this review, the nutritional, microbial, and sensory characteristics of fermented fish are explored to better understand the health benefits along with the safety challenges introduced by fermented fish products. An exploratory approach of the published literature was conducted to achieve the purpose of this review using numerous books and online databases, including Google Scholar, Web of Science, Scopus, ScienceDirect, and PubMed Central, with the goal of obtaining, compiling, and reconstructing information on a variety of fundamental aspects of fish fermentation. This review explores significant information from all available library databases from 1950 to 2022. This review can assist food industries involved in fermented fish commercialization to efficiently ferment and produce better quality products by easing the fermentation process without risking the health and safety of consumers.

Diacylglycerol pre-emulsion prepared through ultrasound improves the gel properties of golden thread surimi

This study determined the influence of diacylglycerol (DAG) pre-emulsion on the gel properties and microstructure of golden thread surimi gels. DAG emulsion stabilized using sodium caseinate was pre-emulsified through ultrasound. The average particle size of DAG pre-emulsion decreased from 1324.15 nm to 41.19 nm, with notable improvements in apparent viscosity and storage stability. The surimi gels with different amounts (0%, 1%, 3%, 5%, and 7% w/w) of DAG pre-emulsion were prepared under heat induction. The whiteness of the composite gels markedly increased with the incorporation of DAG pre-emulsion. The peak T₂₂ value of immobilized water, the gel strength, and water-holding capacity increased gradually, but it slightly decreased with the addition of 7% pre-emulsion. The curve of G' and G″ kept climbing as the concentration of pre-emulsion, and the microstructure of the gel network tended to become denser and more orderly. Principal component analysis (PCA) of electronic nose results showed that the surimi gels containing pre-emulsion could be clearly distinguished from the control group. In conclusion, the addition of 5% DAG pre-emulsion to surimi not only improved gel properties to the highest extent but also be compensated for lipid loss during the rinsing of surimi.

Dynamics and correlation of microbial community and flavor in Pixian Douban fermented with closed process of constant temperature

BACKGROUND

As a Chinese traditional flavor condiment, Pixian Douban (PXDB) is produced using a traditional open fermentation process. In this study, an experimental fermentation of PXDB was conducted at 40 °C for 90 days in a closed system, which has not been applied to PXDB production. The flavor, microbial community and correlations of the samples in the closed system were compared with those in the traditional fermentation.

RESULTS

The content of organic acids and free amino acids in the closed fermentation of constant temperature (CFCT) achieved the standards of product quality, although they were lower than those in the traditional fermentation. Of the 140 detected aroma components, 98 were shared in the two fermentation processes. Enterobacter, Bacteroides and Megamonas were the core microbial genera related to 26 flavor components in the traditional fermentation, while Pantoea was the core microbial genus related to 18 flavor components in CFCT. The CFCT has its own unique advantages over traditional fermentation in forming aromas. It produced a greater impact on the succession of fungi than those of bacteria after changing traditional fermentation to CFCT. The influence of microorganisms on the formation of flavor components was relatively more balanced in CFCT, while the changed fermentation process impacted greatly on the functions of Zygosaccharomomyces and Pichia but little on those of Sphingomonas, Megamonas and Parabacteroides.

CONCLUSION

The study indicated that it was feasible to ferment PXDB in the closed system, and provides a basis to realize controllable PXDB production. © 2020 Society of Chemical Industry.

The relationship between flavor formation, lipid metabolism, and microorganisms in fermented fish products

Traditional fermented fish products are favored due to their unique flavors. The fermentation process of fish is accompanied by the formation of flavor substances through a complex metabolic reaction of microorganisms, especially lipolysis and lipid oxidation. However, it is difficult to precisely control the reaction of microorganisms during the fermentation process in modern industrial production, and fermented fish products have lost their traditional characteristic flavors. The purpose of this review is to summarize the different kinds of fermented fish, core microorganisms in it, and flavor formation mechanisms, providing guidance for industrial cultural starters. Future research on the flavor formation mechanism is necessary to confirm the relationship between flavor formation, lipid metabolism, and microorganisms to ensure stable flavor and safety, and to elucidate the mechanism directly toward industrial application.

Genome sequencing of cold-adapted Planococcus bacterium isolated from traditional shrimp paste and protease identification

BACKGROUND

Psychrophiles have evolved to adapt to freezing environments, and cold-adapted enzymes from these organisms can maintain high catalytic activity at low temperature. The use of cold-adapted enzymes has great potential for the revolution of food and molecular biology industries.

RESULTS

In this study, four different strains producing protease were isolated from traditional fermented shrimp paste, one of which, named Planococcus maritimus XJ11 by 16S rRNA nucleotide sequence analysis, exhibited the largest protein hydrolysis clear zone surrounding the colonies. Meanwhile, the strain P. maritimus XJ11 was selected for further investigation because of its great adaptation to low temperature, low salinity and alkaline environment. The enzyme activity assay of P. maritimus XJ11 indicated that the optimum conditions for catalytic activity were pH 10.0 and 40 °C. Moreover, the enzyme also showed an increasing activity with temperatures from 10 to 40 °C and retained more than 67% activity of the maximum over a broad range of salinity (50-150 g L^-1 ). Genome sequencing analysis revealed that strain XJ11 possessed one circular chromosome of 3 282 604 bp and one circular plasmid of 67 339 bp, with a total number of 3293 open reading frames (ORFs). Besides, 21 genes encoding protease, including three serine proteases, were identified through the NR database.

CONCLUSION

Cold-adapted bacterium P. maritimus XJ11 was capable of producing alkaline proteases with high catalytic efficiency at low or moderate temperatures. Furthermore, the favorable psychrophilic and enzymatic characters of strain P. maritimus XJ11 seem to have a promising potential for industrial application. © 2020 Society of Chemical Industry.