Dynamics of microbial communities, texture and flavor in Suan zuo yu during fermentation

Comprehensive insights into the mechanism of flavor formation in mandarin fish (Siniperca chuatsi) with inoculated fermentation

The inoculated fermentation is an effective way to shorten fermentation time and improve the flavor quality in fermented food. Therefore, this work aims to analyze the difference between traditional and inoculated fermentation, and explore the mechanism of flavor formation in mandarin fish during fermentation. Results showed that a total of 67 volatile compounds were detected, and 13 key flavor compounds were identified in fermented mandarin fish. Inoculation promotes the oxidation and hydrolysis of fatty acids, thus forming more aldehydes and alcohols. Moreover, inoculated fermentation inhibited the growth of Enterococcus, Carnobacterium and Morganella, thereby reducing indole content. In addition, inoculation increased the taste activity values of Glu, Gly and Ala, which improved umami taste and sweet taste of fermented mandarin fish. In short, the mixed inoculation shortened the fermentation time from 12d to 8d, which improved the flavor quality of fermented mandarin fish.

Integration of volatilomics and microbiome diversity reveals key flavor-related metabolic pathways in semi-dried large yellow croaker (Pseudosciaena crocea)

A complex microbial community is critical for developing unique flavors in semi-dried large yellow croaker (Pseudosciaena crocea). Volatilomics analysis identified hexanal, heptanal, nonanal, phenylacetaldehyde, 1-octen-3-ol, and butanoic acid were identified as the key flavor compounds in the fish. Clostridium sensu stricto was the dominant genus, with a relative abundance of 79.78 % after 4 days of air-drying. Validation results showed a positive association between the accumulation of nonanal, phenylacetaldehyde, and butanoic acid and the presence of Clostridium sensu stricto. Significant correlations were also observed between the genera of Lactobacillus and Microbacterium and the key flavor compounds of hexanal and heptanal. Microorganisms contribute to the metabolism of these compounds, primarily through the metabolism of phenylalanine, linoleic acid, linolenic acid, arachidonic acid, and pyruvate. This flavor-regulating role of microorganisms presents them as potential targets for flavor enhancement in traditional aquatic products.

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.

Relationship between physicochemical properties, non-volatile substances, and microbial diversity during the processing of dry-cured Spanish mackerel

To meet the demand of consumers for high-quality dry-cured fish. This study investigates the relationship between microbial diversity and the changes in physicochemical properties and non-volatile flavor compounds of dry-cured Spanish mackerel (DCSM) throughout the curing process. Our findings demonstrate that moisture content significantly decreased during curing, while NaCl generally increased. The nitrite level of 1.52 mg/kg, meeting national safety standards. Additionally, there was a significant increase in hardness and chewiness. The synergistic effect of glutamic acid (Glu), alanine (Ala), and histidine (His) with inosine monophosphate (IMP), adenosine monophosphate (AMP) and guanosine monophosphate (GMP) enhanced the umami taste. Proteobacteria and Photobacteria are the main microorganisms of DCSM at the phylum and genus levels. Proteobacteria and Photobacteria are the main microorganisms of DCSM at the phylum and genus levels. Photobacterium, Moritella, and Pseudomonas were positively correlated with AMP, GMP, Ala, and Glu. And negatively correlated with nitrite and TBARS. These findings suggest that specific microorganisms positively influence the quality of DCSM through their metabolic activities. This research enhances our understanding of flavor formation mechanisms and provides critical insights for optimizing DCSM processing and quality control.

Role of the intestines on the muscle quality of Pacific white shrimp (Litopenaeus vannamei) during chilled storage: Physicochemical and label-free-based peptidomics analyses

The effect of shrimp deveining on the quality of Pacific white shrimp muscle was investigated by analyzing the protein degradation during chilled storage via physicochemical and label-free peptidomics analyses. In this study, shrimp with intact intestines were in the control group (CS), while deveined shrimp (DS) were in the treatment group. The total viability count (TVC), total volatile base nitrogen (TVB-N) content, and trichloroacetic acid (TCA)-soluble peptide content in all of the shrimp groups gradually increased with prolonged chilled storage. However, in the later stages of chilled storage, the DS samples exhibited significantly lower TVB-N, total bacterial, and TCA-soluble peptide contents than the CS samples, indicating that deveining treatment effectively prolonged shrimp quality. The peptidomics analysis revealed varying degrees of protein hydrolysis in the DS and CS samples during chilled storage. A total of 396 differentially abundant peptides (DAPs) were identified in the DS compared with the CS, comprising 98 upregulated and 298 downregulated segments. This suggests that the removal of the intestine effectively inhibits protein hydrolysis. Gene ontology (GO) analysis suggested that the DAPs were mainly involved in catalytic activity, binding, and metabolic processes. The cluster of orthologous groups of protein (COG) analysis showed that the cytoskeleton dynamics of the muscle proteins underwent considerable alterations influenced by the shrimp's intestines during chilled storage.

Dynamic changes in the gel properties, microbial community, and volatile flavor profile of Spanish mackerel (Scomberomorus niphonius) sausages inoculated with Lactiplantibacillus plantarum CY1-2

Spanish mackerel is an important economic fish species in China, but corruption undermines its overall economic value. Fermentation serves as a crucial technique for preserving perishable fish in developing countries. This study aimed to examine the dynamic changes in the gel properties, physicochemical properties, microbial diversity, and volatile flavor compounds (VFCs) of Spanish mackerel sausages inoculated with Lactiplantibacillus plantarum CY1-2 during fermentation. The correlation between key microorganisms and VFCs was explored using a two-way orthogonal partial least squares analysis. The results showed that the group inoculated with strain CY1-2 exhibited significant improvements compared with the control group after 40 h of fermentation. Specifically, gel strength increased by 207.7%, total free amino acids increased by 37.49%, DPPH and ABTS radical scavenging rates increased by 34.12% and 58.73%, and TVB-N levels decreased by 54.2%, respectively. In addition, using gas chromatography-mass spectrometry, 36 VFCs were detected in fermented sausages, including 9 aldehydes, 9 hydrocarbons, 7 alcohols, 4 acids, 2 ketones, and 5 esters. High-throughput sequencing demonstrated that the bacterial profiles were altered in sausages inoculated with strain CY1-2 during fermentation. Enhydrobacter dominated initially but was quickly replaced by Macrococcus after 8 h of fermentation, while Lactobacillus became the dominant genus after 40 h. Correlation analysis revealed that Lactobacillus and Staphylococcus played important roles in the production of VFCs in the fermented sausages. Notably, Lactobacillus was positively associated with 2-undecanone, pentadecane, and hexanal. This study confirmed that strain CY1-2 inoculation could enable the production of high-quality fermented fish sausages.

Changes in protein and volatile flavor compounds of low-salt wet-marinated fermented Golden Pomfret during processing

In this experiment, the changes in protein hydrolysis, protein oxidation, and flavor of low-salt wet-marinated fermented golden pomfret were studied during processing. During processing, a decrease in sulfhydryl content (P < 0.05), a significant increase in protein surface hydrophobicity (P < 0.05), a significant increase in carbonyl content and TCA-soluble peptide (P < 0.05), an increase in TVB-N and amino acid nitrogen (P < 0.05), and a significant increase in the content of free amino acids (P < 0.05), indicating that proteins were gradually oxidized and degraded to small molecules and flavor precursors under the action of bacterial reduction pretreatment, deodorization, marination and fermentation processes, small molecules and aroma precursors was generated by gradual oxidative decomposition. In the course of processing, a total of 113 volatile flavor compounds were identified using GC-MS analysis, while OPLS-DA analysis and VIP value determination led to the identification of 10 characteristic flavor compounds. The results showed that an abundance of flavor compounds was generated during the processing, thereby imparting a more pronounced taste profile to the low-salt wet-marinated fermented golden carp. The results showed that a large number of flavor substances were generated during the processing to give a richer flavor to low-salt wet-marinated fermented golden pomfret that could provide data and theoretical support for the subsequent processing industry of golden pomfret.

Comparative analyses of physicochemical and volatile flavor characteristics in hooked, trawl-net, and radar-net hairtail (Trichiurus haumela) muscles during long-term cryopreservation at -18°C

Chemical analysis showed that pH, b* values, myosin turbidity, carbonyl content, and surface hydrophobicity elevated in hooked, trawl-net, and radar-net hairtail (Trichiurus haumela, HH, TH, and RH) muscles with the prolonged cryopreservation time (-18℃, 120 d). In contrast, L*, a* values, textural properties, and myosin solubility existed decreasing trends. Microstructural results showed that freezing resulted in disordered myofibrils, decreased collagen fibers, widened myofibrillar space, and increased fragmentation in hairtail muscles. Furthermore, volatile flavor analysis suggested that aldehydes, ketones, alcohols, and amines were the key factors for the overall flavor formation in hairtails during cold storage. Pearson correlation coefficient analysis revealed that the color, texture, and protein oxidation had close correlations with VOCs. Among the three different kinds of hairtail, fresh RH fillets exhibited an attractive aroma with high economic value, long-term frozen TH muscle tissues were prone to deterioration in texture, microstructure, and flavor, and the HH samples presented stable quality characteristics and storage performance.

Fermented Fish Products: Balancing Tradition and Innovation for Improved Quality

The flavor profile of fermented fish products is influenced by the complex interplay of microbial and enzymatic actions on the raw materials. This review summarizes the various factors contributing to the unique taste and aroma of these traditional foods. Key ingredients include locally sourced fish species and a variety of spices and seasonings that enhance flavor while serving as cultural markers. Starter cultures also play a critical role in standardizing quality and accelerating fermentation. Flavor compounds in fermented fish are primarily derived from the metabolism of carbohydrates, lipids, and proteins, producing a diverse array of free amino acids, peptides, and volatile compounds such as aldehydes, ketones, alcohols, and esters. The fermentation process can be shortened by certain methods to reduce production time and costs, allowing for faster product turnover and increased profitability in the fermented fish market. Fermented fish products also show potent beneficial effects. This review highlights the importance of integrating traditional practices with modern scientific approaches. Future research directions to enhance the quality of fermented fish products are suggested.

The roles of lipoxygenases and autoxidation during mackerel (Scomberomorus niphonius) dry-cured processing

The roles of enzymatic (Lipoxygenases, LOX) oxidation and autoxidation in the dry-cured processing of mackerel were investigated by adding exogenous substances in this study. Four groups, namely control, chlorogenic acid (inhibiting LOX activity), EDTA-2Na (inhibiting autoxidation), and exogenous LOX (adding eLOX), were assigned. The results showed that lipid oxidation of mackerel was reduced by inhibiting LOX activity and autoxidation, while adding eLOX promoted lipid oxidation. Inhibition of LOX activity and autoxidation suppressed fatty acid accumulation mainly in the air-drying and curing stage, respectively. The total contents of key flavors in the mackerel during dry-cured processing were decreased by inhibiting LOX activity and autoxidation, and the former inhibitory effect was stronger than autoxidation, while it was corresponding increased through adding eLOX, of particular in the later stage of air-drying. Collectively, LOX could promote the flavor formation of the mackerel in the dry-cured processing, which could be applied in the flavor adjustment of aquatic products or some similar fields.

Relationship between the Dynamics of Flavor Compounds and Microbial Succession in the Natural Fermentation of Zhalajiao, a Popular Traditional Chinese Fermented Chili Paste

Zhalajiao, a traditional Chinese fermented food, is popular due to its unique flavor. Traditional Zhalajiao fermentation is closely related to flavor compounds production. However, the mechanisms underlying the formation of these crucial flavor components in Zhalajiao remain unclear. Here, we explored the dynamic changes in physical and chemical properties, microbial diversity, and flavor components of Zhalajiao at various fermentation times. In total, 6 organic acids, 17 amino acids, and 21 key volatile compounds were determined as flavor components. In Zhalajiao, Lactobacillus and Cyanobacterium were the main bacteria that were involved in the formation of crucial flavor compounds. Candida showed a significant correlation with 14 key flavor compounds during fermentation (p < 0.05) and was the main fungal genus associated with flavor formation in Zhalajiao. This research offers a theoretical foundation for the flavor regulation and quality assurance of Zhalajiao.

Fermented fish and fermented fish-based products, an ever-growing source of microbial diversity: A literature review

Fermented fish and fermented fish-based products are part of the diet of many countries all over the world. Their popularity is not only due to the unique flavor, the distinct texture, and the good nutritional quality, but also to the easiness of the production process, that is commonly based on empirical traditional methods. Fish fermentation techniques ususally rely on the combination of some key steps, including salting, addition of spices or additives, and maintenance of anaerobic conditions, thus selecting for the multiplication of some pro-technological microorganisms. The objective of the present review was to provide an overview of the current knowledge of the microbial communities occurring in fermented fish and fish-based products. Specific information was collected from scientific publications published from 2000 to 2022 with the aim of generating a comprehensive database. The production of fermented fish and fish-based foods was mostly localized in West African countries, Northern European countries, and Southeast Asian countries. Based on the available literature, the microbial composition of fermented fish and fish-based products was delineated by using viable counting combined with identification of isolates, and culture-independent techniques. The data obtained from viable counting highlighted the occurrence of microbial groups usually associated with food fermentation, namely lactic acid bacteria, staphylococci, Bacillus spp., and yeasts. The identification of isolates combined with culture-independent methods showed that the fermentative process of fish-based products was generally guided by lactobacilli (Lactiplantibacillus plantarum, Latilactobacillus sakei, and Latilactobacillus curvatus) or Tetragenococcus spp. depending on the salt concentration. Among lactic acid bacteria populations, Lactococcus spp., Pediococcus spp., Leuconostoc spp., Weissella spp., Enterococcus spp., Streptococcus spp., and Vagococcus spp. were frequently identified. Staphylococcus spp. and Bacillus spp. confirmed a great adaptation to fermented fish-based products. Other noteworthy bacterial taxa included Micrococcus spp., Pseudomonas spp., Psychrobacter spp., Halanaerobium spp., and Halomonas spp. Among human pathogenic bacteria, the occurrence of Clostridium spp. and Vibrio spp. was documented. As for yeast populations, the predominance of Candida spp., Debaryomyces spp., and Saccharomyces spp. was evidenced. The present literature review could serve as comprehensive database for the scientific community, and as a reference for the food industry in order to formulate tailored starter or adjunctive cultures for product improvement.

Transforming the fermented fish landscape: Microbiota enable novel, safe, flavorful, and healthy products for modern consumers

Regular consumption of fish promotes sustainable health while reducing negative environmental impacts. Fermentation has long been used for preserving perishable foods, including fish. Fermented fish products are popular consumer foods of historical and cultural significance owing to their abundant essential nutrients and distinct flavor. This review discusses the recent scientific progress on fermented fish, especially the involved flavor formation processes, microbial metabolic activities, and interconnected biochemical pathways (e.g., enzymatic/non-enzymatic reactions associated with lipids, proteins, and their interactions). The multiple roles of fermentation in preservation of fish, development of desirable flavors, and production of health-promoting nutrients and bioactive substances are also discussed. Finally, prospects for further studies on fermented fish are proposed, including the need of monitoring microorganisms, along with the precise control of a fermentation process to transform the traditional fermented fish to novel, flavorful, healthy, and affordable products for modern consumers. Microbial-enabled innovative fermented fish products that consider both flavor and health benefits are expected to become a significant segment in global food markets. The integration of multi-omics technologies, biotechnology-based approaches (including synthetic biology and metabolic engineering) and sensory and consumer sciences, is crucial for technological innovations related to fermented fish. The findings of this review will provide guidance on future development of new or improved fermented fish products through regulating microbial metabolic processes and enzymatic activities.

Flavor Formation in Dry-Cured Fish: Regulation by Microbial Communities and Endogenous Enzymes

Dried salted fish is a traditional dry-cured fish that is sprinkled with salt before the curing process. With a unique flavor as well as diverse varieties, dry-cured fish is popular among consumers worldwide. The presence of various microbial communities during the curing process leads to numerous metabolic reactions, especially lipid oxidation and protein degradation, which influence the formation of flavor substances. However, during industrial curing, the quality of dry-cured fish is difficult to control, leading to the formation of products with diverse flavors. This review describes the curing process of dried salted fish, the key microorganisms involved in the curing process of typical dried salted fish products at home and abroad, and the correlation between biological metabolism and flavor formation and the underlying mechanism. This review also investigates the prospects of dried salted fish products, proposing methods for the analysis of improved curing processes and the mechanisms of dried salted fish. Through a comprehensive understanding of this review, modern production challenges can be addressed to achieve greater control of microbial growth in the system and improved product safety. In addition to advancing our understanding of the processes by which volatile flavor compounds are formed in conventional dry-cured fish products, we expect that this work will also offer a theoretical framework for enhancing their flavor in food processing.

Core microbes closely related with the nutrients and flavor of sweet fermented oats (whole grain food) from China

Increased attention has been given to whole grain and plant-based foods due to health concerns. Sweet fermented oats (SFOs) are such traditional fermented food from China. However, reports on their microbiota and relations with the nutrients and flavor were scarcely few, hindering their wider application. The comprehensive microbial composition, metabolic compounds and their correlations of representative SFOs from northwestern China were firstly investigated. Firmicutes predominated the microbial communities, followed by Proteobacteria. Weissella, Bacillus and Lactobacillus were dominant bacterial genera, biomarkers and core bacteria as well. GC-MS (Gas Chromatography-Mass Spectrometer) identified the metabolic compounds, among which the categories fatty acids and carboxylic acids most abundant. Eighteen chemicals showed significant differences among the five SFOs, including ethyl octanoate, neryl acetate, L-sorbose, diglycerol, cellotetraose etc. Fatty acids, carboxylic acids, amino acids, peptides, oligosaccharides, and monosaccharides were the key substances responsible for the unique flavor and rich nutrients in SFOs. The core bacteria were closely related to chemical acids, esters, flavone and alcohol. Pediococcus showed a negative correlation with 2,3-butanediol. SFOs were made in the laboratory with the core bacterial strains, obtaining a high abundance of nutrient chemicals and sensory evaluation value. The research provided a foundation for the improvement, further application and industrialization of SFOs.

Bacterial community structure, predicted metabolic activities, and formation of volatile compounds attributed to Malaysian fish sauce flavour

The fermentation of Malaysian fish sauce (budu) varies from one to twelve months depending on the producer, resulting in inconsistent quality. The microbiota, their predicted metabolic pathways and volatile metabolites profiles were determined at different stages of budu fermentation. Budu fermented for 1 and 3 months were characterized by the presence of Gram negative Enterobacterales, Gammaproteobacteria, and Fusobacteriaceae, which continuously decrease in abundance over fermentation time. The metabolic pathways prediction grouped 1- and 3- month budu in a cluster enriched with degradation reactions. 6-month budu were dominated by Halanaerobium and Staphylococcus, while the 12-month were dominated by Lentibacillus, Bacilli, and Halomonas. Biosynthesis-type predicted pathways involving protein and lipid derivatives were enriched in 6- and 12-month fermented budu, accumulating 2,6-dimethylpyrazine, methyl 2-ethyldecanoate, 2-phenylacetaldehyde, 3-methylbutanal, and 3-methylbutanoic acid. These compounds may indicate budu maturity and quality. This result may assist as a reference for quality control and fermentation monitoring.

Application and Effect of Pediococcus pentosaceus and Lactiplantibacillus plantarum as Starter Cultures on Bacterial Communities and Volatile Flavor Compounds of Zhayu, a Chinese Traditional Fermented Fish Product

Zhayu is a type of traditional fermented fish product in China that is made through the fermentation of salted fish with a mixture of cereals and spices. Inoculation fermentation was performed using Pediococcus pentosaceus P1, Lactiplantibacillus plantarum L1, and a mixture of two strains, which were isolated from cured fish in Hunan Province. Compared with the natural fermentation, inoculation with lactic acid bacteria (LAB) accelerated the degradation of myosin and actin in Zhayu, increased the trichloroacetic acid (TCA)-soluble peptide content by about 1.3-fold, reduced the colony counts of Enterobacteriaceae and Staphylococcus aureus by about 40%, and inhibited their lipid oxidation. In the texture profile analysis performed, higher levels of hardness and chewiness were observed in the inoculation groups. In this study, the bacterial community and volatile flavor compounds were detected through 16S high-throughput sequencing and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). Inoculation with L. plantarum L1 reduced around 75% abundance of Klebsiella compared with the natural fermentation group, which was positively correlated with 2,3-Butanediol, resulting in a less pungent alcohol odor in Zhayu products. The abundances of 2-pentylfuran and 2-butyl-3-methylpyrazine were increased over threefold in the L1 group, which may give Zhayu its unique flavor and aroma.

A multi-omics-based investigation into the flavor formation mechanisms during the fermentation of traditional Chinese shrimp paste

The fermentation process of traditional shrimp paste is closely associated with the production of flavor substances, but the formation mechanism of key aroma components is still unclear. In this study, a comprehensively flavor profile analysis of traditional fermented shrimp paste was carried out by E-nose and SPME-GC-MS. A total of 17 key volatile aroma components with OAV > 1 contributed greatly to the overall flavor formation of shrimp paste. In addition, high-throughput sequencing (HTS) analysis revealed that Tetragenococcus was the dominant genera in the whole fermentation process. Moreover, metabolomics analysis showed that the oxidation and degradation of lipids, protein, organic acids and amino acids produced a large number of flavor substances and intermediates, which laid the foundation for the Maillard reaction in term of generating the distinct aroma of the traditional shrimp paste. This work will provide theoretical support for the realization of flavor regulation and quality control in traditional fermented foods.

Novel insight into flavor and quality formation in naturally fermented low-salt fish sauce based on microbial metabolism

Low-salt fermentation is an effective way to shorten the fermentation time of fish sauce. In this study, the changes of microbial community, flavor, and quality during the natural fermentation of low-salt fish sauce were studied, followed by the elucidation of flavor and quality formation mechanisms based on microbial metabolism. The 16S rRNA gene high-throughput sequencing showed that both richness and evenness of microbial community were reduced during fermentation. The microbial genera, including Pseudomonas, Achromobacter, Stenotrophomonas, Rhodococcus, Brucella, and Tetragenococcus were more suitable for the fermentation environment, and obviously increased along with the fermentation. There were a total of 125 volatile substances identified by HS-SPME-GC-MS, of which 30 substances were selected as the characteristic volatile flavor substances, mainly including aldehydes, esters, and alcohols. Large amounts of free amino acids were produced in the low-salt fish sauce, especially umami and sweet amino acids, as well as high concentrations of biogenic amines. Correlation network constructed by the Pearson's correlation coefficient showed that most characteristic volatile flavor substances were significantly positively correlated with Stenotrophomonas, Achromobacter, Rhodococcus, Tetragenococcus, and Brucella. Stenotrophomonas and Tetragenococcus were significantly positively correlated with most free amino acids, especially umami and sweet amino acids. Pseudomonas and Stenotrophomonas were positively correlated with most biogenic amines, especially histamine, tyramine, putrescine, and cadaverine. Metabolism pathways suggested that the high concentrations of precursor amino acids contributed to the production of biogenic amines. This study indicates that the spoilage microorganisms and biogenic amines in the low-salt fish sauce need to be further controlled, and the strains belonging to Tetragenococcus can be isolated as potential microbial starters for the production of low-salt fish sauce.

Unraveling the microbial succession during the natural fermentation of grass carp and their correlation with volatile flavor formation

Complex microbial communities contribute significantly to the flavor formation of traditional fermented fish products. However, the relationship between microorganisms and flavor formation in traditional fermented grass carp products is still unclear. In this study, the diversity and succession of microbial communities and the variation of volatile compounds during natural fermentation of grass carp were analyzed using high-throughput sequencing of 16S rRNA and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS), respectively. The core functional microorganism and key volatile compounds were identified, and their potential relationship was revealed using a correlation network model analysis. The microbial community analysis result showed that the microbial diversity during natural fermentation of grass carp decreased markedly with increasing fermentation time, and Lactiplantibacillus, Staphylococcus, and Enterobacter were the dominant genera in naturally fermented grass carp. HS-SPME-GC-MS analysis result showed that 45 volatile compounds were identified from fermented samples, among which 13 compounds (e.g., hexanal, heptanal, nonanal, decanal, 3-octanone, 3-methyl-1-butanol, 1-hexanol, 1-heptanol, 1-octen-3-ol, 1-octanol, ethyl acetate, 3-methyl-1-butanol acetate, and 2-methoxy-4-vinylphenol) were identified as the key volatile compounds. Additionally, the correlation network model analysis result revealed that Lactiplantibacillus showed significantly positive correlations with most of the key volatile compounds, making an important contribution to the formation of volatile flavor in naturally fermented grass carp. This study may lead to an understanding of the role of core functional microorganisms in the formation of volatile flavor during the natural fermentation of grass carp and provide some theoretical guidance for the industrial production of high-quality fermented grass carp products.

Further Interpretation of the Volatile, Microbial Community and Edible Quality of Fresh Fermented Rice Noodles with Different Selected Strains

Understanding bacteria and yeasts can reduce unpredictable changes in fresh fermented rice noodles (FFRN). The effects of selected strains (Limosilactobacillus fermentum, Lactoplantibacillus plantarum, Lactococcus lactis and Saccharomyces cerevisiae) on the edible quality, microbial community, and volatile component of FFRN were studied. The results indicated that the fermentation time could be shortened to 12 h when Limosilactobacillus fermentum, Lactoplantibacillus plantarum, and Lactococcus lactis were added, whereas it still required approximately 42 h after adding Saccharomyces cerevisiae. Only a steady bacterial composition was provided by adding Limosilactobacillus fermentum, Lactoplantibacillus plantarum, and Lactococcus lactis, and only a steady fungal composition was provided by adding Saccharomyces cerevisiae. Therefore, these microbial results indicated that the selected single strains cannot improve the safety of FFRN. However, the cooking loss was decreased from 3.11 ± 0.11 to 2.66 ± 0.13 and the hardness of FFRN was increased from 1186 ± 178 to 1980 ± 207 when it was fermented with single strains. Finally, a total of 42 volatile components were determined by Gas chromatography-ion Mobility Spectrometry and 8 aldehydes, 2 ketones, and 1 alcohol were added during the entire fermentation process. The main volatile components were different during fermentation depending on the added strain, and there was the greatest variety of volatiles in the group with added Saccharomyces cerevisiae.

Deciphering Microbial Diversity and Functional Codes of Traditional Fermented Whole Grain Tianpei from Typical Regions of China

Whole grains are a crucial part of healthy and sustainable diets, attracting great attention. Tianpei is a popular traditional fermented whole grain food and beverage from China. It is suitable for all ages with lots of health benefits. However, its microflora and their functions, relations between microbial taxa and functions with Tianpei properties, were still little informed, limiting the fermentation optimization and quality improvement. In this study, the characteristics and distribution of the microbial flora taxa and their functions of the fermented whole grain Tianpei from typical regions of China were mainly deciphered through metagenomic methods. Phyla Mucoromycota, Firmicutes, Ascomycota, and Proteobacteria were the most abundant. Rhizopus, Limosilactobacillus, and Lactobacillus were the most abundant genera. Microbial COG functions carbohydrate transport and metabolism (mainly including fructose, galactose, glucose, L-arabinose, and mannose) and amino acid transport and metabolism (mainly including arginine, asparagine, glutamine, and glycine) kept a high abundance. PCA (Principal Component Analysis) illustrated that the microbial community and their functions of every Tianpei sample clustered individually based on the analysis, NR, related with the factors of raw material and sources. The microbial taxa, microbial functions, and the Tianpei properties were significantly correlated. Rhizopus, Limosilactobacillus, and Lactobacillus contributed most COG functions in Tianpei samples. Analysis of quorum sensing, pfam, secretion protein, probio, and cytochromes P450 were also annotated and found among Tianpei microbial communities. A sum of 105 probiotics were classified, mainly belonging to Lactobacillus, Leuconostoc, Acetobacter, Bacillus, Bifidobacterium, Pediococcus, etc. Tianpei samples made in the library with the most abundant and functional microbial key taxa strains—Rhizophus oryzae, Lactobacillus plantarum, and Limosilactobacillus fermentum—showed rich nutrient chemicals. The results indicate that microbial taxa and their functions could determine Tianpei properties. Thus, the quality /nutrients, flavor, and industrial production of Tianpei could be further investigated, promoted, and improved in the future based on the characteristics of these microbial taxa and their functions, such as the regulations of the main carbohydrate and AA. The study will also lay a foundation for the fermentative characteristics and condition technology of fermented whole grain food.

Application progress of intelligent flavor sensing system in the production process of fermented foods based on the flavor properties

Fermented foods are sensitive to the production conditions because of microbial and enzymatic activities, which requires intelligent flavor sensing system (IFSS) to monitor and optimize the production process based on the flavor properties. As the simulation system of human olfaction and gustation, IFSS has been widely used in the field of food with the characteristics of nondestructive, pollution-free, and real-time detection. This paper reviews the application of IFSS in the control of fermentation, ripening, and shelf life, and the potential in the identification of quality differences and flavor-producing microbes in fermented foods. The survey found that electronic nose (tongue) is suitable to monitor fermentation process and identify food authenticity in real time based on the changes of flavor profile. Gas chromatography-ion mobility spectrometry and nuclear magnetic resonance technology can be used to analyze the flavor metabolism of fermented foods at various production stages and explore the correlation between flavor substances and microorganisms.

Dynamic change of bacterial diversity, metabolic pathways, and flavor during ripening of the Chinese fermented sausage

Chinese fermented sausage is a famous fermented meat product with a complex microbiota that has a potential impact on flavor and quality. In this study, Lactobacillus plantarum MSZ2 and Staphylococcus xylosus YCC3 were used as starter cultures to investigate the change in bacterial diversity, metabolic pathways, and flavor compounds during the ripening process of fermented sausages. High-throughput sequencing technology and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC/MS) were applied for characterizing the profiles of bacterial diversity, metabolic pathways, and flavor compounds in sausage samples on days 0, 6, and 12 during ripening. Results showed that Lactobacillus, Staphylococcus, Lactococcus, Leuconostoc, and Weissella were the most abundant bacterial genera found in the sausage samples during all stages of fermentation. Functional prediction reveals the abundance of 12 different metabolic pathways, the most important pathways are carbohydrate metabolism, nucleotide metabolism, lipid metabolism, and amino acid metabolism. A total of 63 volatile compounds were successfully identified in fermented sausage samples. Correlational analysis demonstrated that Staphylococcus and Leuconostoc were closely related to the formation of flavor compounds. Therefore, the present study may provide guidance for future use of microbiota to improve flavor, quality, and preservation of fermented sausages.

Insights into the flavor perception and enhancement of sodium-reduced fermented foods: A review

Salt (sodium chloride, NaCl) is a vital ingredient in fermented foods, which affects their safety, texture, and flavor characteristics. Recently, the demand for reduced-sodium fermented foods has increased, as consumers have become more health-conscious. However, reducing sodium content in fermented foods may negatively affect flavor perception, which is a critical quality attribute of fermented foods for both the food industry and consumers. This review summarizes the role of salt in the human body and foods and its role in the flavor perception of fermented foods. Current sodium reduction strategies used in the food industry mainly include the direct stealth reduction of NaCl, substituting NaCl with other chloride salts, and structure modification of NaCl. The odor-induced saltiness enhancement, application of starter cultures, flavor enhancers, and non-thermal processing technology are potential strategies for flavor compensation of sodium-reduced fermented foods. However, reducing sodium in fermented food is challenging due to its specific role in flavor perception (e.g., promoting saltiness and volatile compound release from food matrices, inhibiting bitterness, and changing microflora structure). Therefore, multiple challenges must be addressed in order to improve the flavor of low-sodium fermented foods. Future studies should thus focus on the combination of several strategies to compensate for the deficiencies in flavor resulting from sodium reduction.

Quality Improvement of Zhayu, a Fermented Fish Product in China: Effects of Inoculated Fermentation with Three Kinds of Lactic Acid Bacteria

To investigate the effects of inoculation fermentation on the quality of Zhayu (a traditional fermented fish product in China), different amounts of L. plantarum, P. acidilactici, and P. pentosaceus were inoculated into samples, and the safety, nutritional, textural, and flavor properties of the samples were evaluated. Fermentation with lactic acid bacteria (LAB) decreased pH values and total volatile basic nitrogen content. The addition of 10⁸~10⁹ cfu/100 g LAB significantly increased the content of crude fat and water-soluble proteins in Zhayu. The addition of L. plantarum and P. acidilactici increased the content of soluble solids in Zhayu. Moreover, fermentation with LAB made the products tender and softer, and the samples prepared with 10⁹ cfu/100 g LAB presented better overall qualities. Additionally, Zhayu fermented with L. plantarum and P. acidilactici showed the strongest sourness, while the samples prepared with P. pentosaceus showed the strongest umami taste, consistent with the highest contents of Asp (25.1 mg/100 g) and Glu (67.8 mg/100 g). The addition of LAB decreased the relative contents of aliphatic aldehydes, (Z)-3-hexen-1-ol, and 1-octen-3-ol, reducing the earthy and fishy notes. However, LAB enhanced the contents of terpenoids, acids, esters, and S-containing compounds, increasing the sour, pleasant, and unique odors of Zhayu.

Development of probiotics beverage using cereal enzymatic hydrolysate fermented with Limosilactobacillus reuteri

Although most probiotic products are milk based, lactose intolerance and vegetarianism inspired the idea of developing nondairy probiotic products. In this study, probiotic beverages were produced from four enzymatically hydrolyzed cereal substrates (coix seed, quinoa, millet, and brown rice) and fermented by Limosilactobacillus reuteri. Fermentation parameters, including pH, titratable acidity, viable count, organic acids, and volatile components were determined. Results showed that the pH values decreased and titratable acidity increased with the fermentation process (p < .05). Although the final pH in all samples was below 4.0, the growth of L. reuteri was not significantly inhibited by low pH. The number of viable bacteria (12.96 log CFU/ml) in coix seed substrate was significantly higher than that in other samples after the fermentation for 24 h (p < .05). Lactic acid and acetic acid were the main organic acids after fermentation and the highest in quinoa (lactic acid: 7.58 mg/ml; acetic acid: 2.23 mg/ml). The flavor analysis indicated that there were differences in the flavor components of different cereal beverages. Forty-nine volatile compounds were identified in four beverages, including acids, alcohols, aldehydes, ketones, and esters. The results of the electronic tongue showed that the umami taste of the fermented coix seed was better than that of other samples, displaying the more pleasant taste characteristics. In conclusion, it is feasible to prepare probiotic symbiotic cereal beverage with L. reuteri as starter culture. This study provides a reference for the development of nondairy probiotic products.

Insight into the Characterization of Volatile Compounds in Smoke-Flavored Sea Bass (Lateolabrax maculatus) during Processing via HS-SPME-GC-MS and HS-GC-IMS

The present study aimed to ascertain how the volatile compounds changed throughout various processing steps when producing a smoke-flavored sea bass (Lateolabrax maculatus). The volatile compounds in different production steps were characterized by headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) and headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS). A total of 85 compounds were identified, and 25 compounds that may be considered as potential key compounds were screened by principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA). Results indicated that aldehydes were the major volatile compounds throughout the processing. The characteristic volatile compound in fresh samples was hexanol, and curing was an effective method to remove the fishy flavor. The concentration of volatile compounds was significantly higher in dried, smoked, and heated samples than in fresh and salted samples. Aldehydes accumulated because of the drying process, especially heptanal and hexanal. Smoke flavoring was an important stage in imparting smoked flavor, where phenols, furans and ketones were enriched, and heating leads to the breakdown of aldehydes and alcohols. This study will provide a theoretical basis for improving the quality of smoke-flavored sea bass products in the future.

Improving the Flavor of Fermented Sausage by Increasing Its Bacterial Quality via Inoculation with Lactobacillus plantarum MSZ2 and Staphylococcus xylosus YCC3

This research aims to investigate the effects of Staphylococcus xylosus YCC3 (Sx YCC3) and Lactobacillus plantarum MSZ2 (Lp MSZ2) on lipid hydrolysis and oxidation, the bacterial community’s composition, and the volatile flavor compounds in fermented sausage. The bacterial community was examined by plate counting and high-throughput sequencing. Differential flavor compounds in non-inoculated and inoculated sausages were identified by principal component analysis (PCA) and orthogonal partial least squares discrimination analysis (OPLS-DA). The results showed that the free fatty acid (FFA) content was increased after inoculating with Sx YCC3 or Lp MSZ2. The pH, peroxide value (POV), thiobarbituric acid reactive substances (TBARS) value, lipoxygenase activity, and the counts of Enterobacteriaceae were lower in the inoculated sausage than in the non-inoculated sausage. The bacterial inoculation enhanced the competitiveness of Staphylococcus and Lactobacillus and restricted the growth of unwanted bacteria. The OPLS-DA revealed that (Z)-hept-2-enal, (E)-2-octenal, 1-nonanal, octanal, and 1-octen-3-ol were common differential flavor compounds that were found in the inoculated sausages but were not found in the non-inoculated sausages. A positive correlation was observed between the differential flavor compounds and the relative abundance of Staphylococcus or Lactobacillus, or the FFA content. Our results indicated that inoculation with Sx YCC3 or Lp MSZ2 can improve fermented sausages’ flavor by enhancing their bacterial quality and increasing their FFA content.

Recent trends in microbial flavour Compounds: A review on Chemistry, synthesis mechanism and their application in food

Aroma and flavour represent the key components of food that improves the organoleptic characteristics of food and enhances the acceptability of food to consumers. Commercial manufacturing of aromatic and flavouring compounds is from the industry's microbial source, but since time immemorial, its concept has been behind human practices. The interest in microbial flavour compounds has developed in the past several decades because of its sustainable way to supply natural additives for the food processing sector. There are also numerous health benefits from microbial bioprocess products, ranging from antibiotics to fermented functional foods. This review discusses recent developments and advancements in many microbial aromatic and flavouring compounds, their biosynthesis and production by diverse types of microorganisms, their use in the food industry, and a brief overview of their health benefits for customers.

Low-Content Pre-Emulsified Safflower Seed Oil Enhances the Quality and Flavor of the Nemipterus Virgatus Surimi Gel

Surimi-based products occupy an important position in the aquatic product processing industry. To enhance the quality and flavor of surimi-based products, the effects of pre-emulsified safflower seed oil on the texture, water-holding capacity (WHC), microstructure, and flavor of Nemipterus virgatus surimi gel was evaluated. The texture and whiteness of the gel were improved, and the WHC increased (p < 0.05) as the content of safflower seed oil increased up to 2 mL per 100 g surimi. Furthermore, the drops of pre-emulsified safflower seed oils with an average diameter of less than 0.10 μm were evenly distributed in gel matrix. Microstructure and infrared spectroscopy analyses indicated that low-content pre-emulsified safflower seed oil acted as filler particles to occupy void spaces, resulting in gel exhibiting a dense network structure. Volatile analysis showed the gel containing pre-emulsified oil enriched volatile compounds, mainly resulting from the oxidation and decomposition of oils by the activation of lipoxygenase, which synergistically contributes to unique flavors of gel. Consequently, low-content pre-emulsified safflower seed oil can used to enhance the quality and flavor of N. virgatus surimi-based products. These findings are especially relevant to the current growing interest in low-fat and high-protein diets.

Analysis of the relationship between microorganisms and flavour development in dry-cured grass carp by high-throughput sequencing, volatile flavour analysis and metabolomics

Complex microbial community plays an important role for flavor formation in traditional dry-cured grass carp. To investigate the correlation between microorganisms and flavour development, the bacterial diversity and flavour quality of dry-cured fish at different stages of fermentation were analysed using high-throughput sequencing, volatile flavour analysis and metabolomics. Cobetia, Staphylococcus and Ralstonia were the dominant genera in dry-cured fish, with relative abundances of 37.78%, 34.46% and 3.2%, respectively. The flavour of dry-cured fish samples varied as the abundance of aldehydes, alcohols, small peptides, FAAs and carboxylic acids showed a great increase during fermentation. Moreover, there were significant correlations (P < 0.05) between specific microorganisms and volatile indicators, as well as flavour metabolites. Staphylococcus, as the dominant bacterial genus, is involved in the mechanism of flavour formation in dry-cured fish during fermentation. This information is useful for elucidating the mechanism of flavour formation in dry-cured fish.