• Review article

• Open access

• Published: 20 October 2025

• Zohaib Ali1,2,3,

• Ulrich Freddy Nziengui Mbadinga1,2,3,

• Shuyao Wen1,2,3,

• Xiaoyi Hou1,2,3 &

• …

• Jianhui Wang ORCID: orcid.org/0000-0003-0625-24471,2,3

Journal of Ethnic Foods volume 12, Article number: 34 (2025) Cite this article

Abstract

Fermented vegetables are globally appreciated for their distinctive flavors and advantageous health effects. Fermentation enhances the nutritive quality, flavor, and lifespan of food products. Fermented vegetable flavor profiles are intricately linked to microbiota assessment and progression. Flavor primarily consists of taste, aroma, tactile and temperature factors. Several metabolic pathways produce flavor-active compounds from precursors found in the raw materials. This review assesses the role of lactic acid bacteria in influencing metabolic pathways, including lipid metabolism, as well as carbohydrate and amino acid metabolism, which are responsible for producing aromatic compounds that contribute to flavor formation in fermented vegetables. Moreover, the review highlights key factors (temperature, pH, salts levels, oxygen availability and substrate availability) that affect flavor formation, and explores flavor profile of popular Chinese fermented vegetable products, such as Sauerkraut, Sichuan paocai, Dongbei suancai, and Jiangxi yancai that are widely consumed in.

Introduction

Fermentation, a conventional technique for preserving food, not only extends the lifespan and nutritious content of food but also adds distinctive and intricate flavors [[1](#ref-CR1 “Wang Y, et al. Insights into microbiota community dynamics and flavor development mechanism during golden pomfret (Trachinotus ovatus) fermentation based on single-molecule real-time sequencing and molecular networking analysis. Food Sci Hum Wellness. 2024;13(1):101–14. https://doi.org/10.26599/FSHW.2022.9250008

.“),[2](#ref-CR2 “Zhang J, et al. Metagenomics-based insights into the microbial community profiling and flavor development potentiality of baijiu Daqu and huangjiu wheat Qu. Food Res Int. 2022;152:110707. https://doi.org/10.1016/j.foodres.2021.110707

.“),[3](#ref-CR3 “Chen C, et al. Dynamics of microbial communities associated with flavor formation during sour juice fermentation and the milk fan drying process. J Dairy Sci. 2023;106(11):7432–46. https://doi.org/10.3168/jds.2023-23244

.“),[4](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR4 “Chen Z, et al. Relationship between microbial community and flavor profile during the fermentation of chopped red chili (Capsicum annuum L.). Food Biosci. 2022;50:102071. https://doi.org/10.1016/j.fbio.2022.102071

.“)]. The technique of fermenting vegetables has gained fresh attention because of its distinct flavors, potential to promote innovation, the cost-effectiveness of the procedure and health advantages [[5](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR5 “Thierry A, et al. Lactofermentation of vegetables: an ancient method of preservation matching new trends. Trends Food Sci Technol. 2023. https://doi.org/10.1016/j.tifs.2023.07.009

.“)]. Fermented vegetables, including iconic products like kimchi in Asia, olives in Southern Europe, sauerkraut in Central and Eastern Europe, and, are popularly consumed worldwide. In western Europe, except for olives and sauerkraut, fermented vegetables are not widely consumed [[6](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR6 “Medina-Pradas E, et al. Review of vegetable fermentations with particular emphasis on processing modifications, microbial ecology, and spoilage. In: The microbiological quality of food. 2017, Elsevier. p. 211–236. https://doi.org/10.1016/B978-0-08-100502-6.00012-1

“), [7](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR7 “Tamang JP, et al. Fermented foods in a global age: East meets West. Compr Rev Food Sci Food Saf. 2020;19(1):184–217. https://doi.org/10.1111/1541-4337.12520

.“)].

The traditional significance is not only the reason for the global recognition of fermented vegetables but distinct biochemical adaptations that impart their sensory characteristics also played their part. Flavor profiles are also shaped by these adaptations governed by microbial involvement. During vegetable fermentation, the microbial metabolites generated have a crucial role in the flavor formation. Microorganisms metabolize fermentable substrates, primarily proteins and carbohydrates, into physiologically active compounds, including volatiles, free amino acids (FAA), organic acids, sugar, and short-chain fatty acids (SCFAs). These metabolites enhance the beneficial nutritional qualities appealing flavors of fermented vegetables [[8](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR8 “Septembre-Malaterre A, Remize F, Poucheret P. Fruits and vegetables, as a source of nutritional compounds and phytochemicals: changes in bioactive compounds during lactic fermentation. Food Res Int. 2018;104:86–99. https://doi.org/10.1016/j.foodres.2017.09.031

.“), [9](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR9 “Rajendran S, Silcock P, Bremer P. Flavour volatiles of fermented vegetable and fruit substrates: a review. Molecules. 2023;28(7):3236. https://doi.org/10.3390/molecules28073236

.“)]. Every variety of fermented vegetables often contains a unique community of microbes. Probiotics, namely lactic acid bacteria (LABs) play a vital role in fermented vegetables. They enhance flavor and generate useful substances, suppress pathogenic microbes, and decrease the presence of detrimental components [[10](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR10 “Armenova N, et al. Microbial detoxification of residual pesticides in fermented foods: current status and prospects. Foods. 2023;12(6):1163. https://doi.org/10.3390/foods12061163

.“), [11](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR11 “Baralić K, et al. Probiotic cultures as a potential protective strategy against the toxicity of environmentally relevant chemicals: state-of-the-art knowledge. Food Chem Toxicol. 2023;172:113582. https://doi.org/10.1016/j.fct.2022.113582

.“)].

The genera of LABs comprise Lactobacillus, Weissella, Leuconostoc, Streptococcus, Enterococcus, Pediococcus, Lactococcus, and several more [[12](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR12 “Reuben RC, et al. Isolation, characterization, and assessment of lactic acid bacteria toward their selection as poultry probiotics. BMC Microbiol. 2019;19:1–20. https://doi.org/10.1186/s12866-019-1626-0

.“), [13](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR13 “Hatti-Kaul R, et al. Lactic acid bacteria: from starter cultures to producers of chemicals. FEMS Microbiol Lett. 2018;365(20):fny213. https://doi.org/10.1093/femsle/fny213

.“)]. In fermented foods, the primary function of LAB is to convert carbohydrates into lactic acid that effectively acidifies the food medium. Therefore, enhancing microbiological safety and the shelf life of the products. In addition, most lactic acid bacteria (LAB) in fermented foods are responsible for flavor formation [[14](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR14 “De Vuyst L, Neysens P. The sourdough microflora: biodiversity and metabolic interactions. Trends Food Sci Technol. 2005;16(1–3):43–56. https://doi.org/10.1016/j.tifs.2004.02.012

.“), [15](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR15 “Thierry A, et al. Production of flavor compounds by lactic acid bacteria in fermented foods. Biotechnology of lactic acid bacteria: novel applications, 2015: p. 314–340. https://doi.org/10.1002/9781118868386.ch19

“)]. Flavor remains widely acknowledged as one of the best essential characteristics of food for consumers. The biochemical transformation of many food components is involved in the flavor formation, as this process is very complex. To effectively control the formation of flavors in food, it is important to have a comprehensive understanding of this process [[16](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR16 “Verma DK, Srivastav PP. A paradigm of volatile aroma compounds in rice and their product with extraction and identification methods: a comprehensive review. Food Res Int. 2020;130:108924. https://doi.org/10.1016/j.foodres.2019.108924

.“)]. Priory, in fermentation, microbial involvement has been extensively studied but still it lacked a comprehended understanding of the specific mechanisms by which LAB strains interact and play their role in aroma compound formation in fermented vegetables. The current review aims to bridge this gap by exploring different metabolic mechanisms that lead to the development of distinct flavors and assessing key contributors that affect the sensory profile in fermented vegetables. The objective of this article review is to assess the significance of flavor and offer an understanding of the involvement of different microorganisms in the process of flavor formation. The article emphasized the distinct metabolic paths responsible for vegetable fermentation, which lead to the aroma compounds formation. Furthermore, this research provides an understanding of several aspects that have affected the formation of flavor during fermentation, as well as popular fermented vegetable products that are widely consumed.

Methodology of review

This review was conducted to provide a comprehensive understanding of the role of lactic acid bacteria in flavor formation in Chinese traditional fermented vegetable products. In this study, the keywords used to collect the relevant literature were vegetable fermentation, flavor formation, Sauerkraut, Sichuan paocai, Dongbei suancai, Jiangxi yancai, lactic acid bacteria in vegetable fermentation, key flavors of traditional fermented products, volatile flavor compounds during fermentation, and microbial metabolism. The sources used in this review article were collected from various well-known databases, such as Google Scholar, Science Direct, Springer, Elsevier, PubMed, and Wiley Online Library. The cited studies were reviewed ranged from publication dated 1996 to 2024.

Significance of Flavor

The flavor is a multifaceted experience that primarily consists of aroma, taste, temperature and tactile elements [[17](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR17 “Reineccius G. Choosing the correct analytical technique in aroma analysis G. Reineccius, University of Minnesota, USA. Flavour in food, 2006: p. 81. http://ndl.ethernet.edu.et/bitstream/123456789/43975/1/119.pdf#page=94

“)]. The human tongue contains taste receptors that enable it to differentiate between four fundamental tastes: sour, sweet, bitter, and salty. Additionally, umami is the unique terminology that encompasses a fifth taste sensation. The sour taste serves a primary function in detecting rotten or unripe food, and this may be attributed to the presence of organic acids. The sensation of saltiness, similar to sourness, is activated by ions. Therefore, these receptors are essential for evaluating the concentration of electrolytes. The level of concentration affects whether the sensation is enjoyable or not [[18](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR18 “Chandrashekar J, et al. The cells and peripheral representation of sodium taste in mice. Nature. 2010;464(7286):297–301. https://doi.org/10.1038/nature08783

.“)]. The function of sweet and savory receptors is to signal the energy value of food, and these receptors are activated by saccharides, whereas umami receptors are primarily activated by amino acids [[19](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR19 “Li X, et al. Human receptors for sweet and umami taste. Proc Natl Acad Sci USA. 2002;99(7):4692–6. https://doi.org/10.1073/pnas.072090199

.“)]. Bitter receptors are designed to detect any potentially harmful substances, such as bacterial byproducts or spoiled items. Bitterness is the most intricate of human tastes and is widely regarded as the most significant [[20](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR20 “Beckett EL, et al. Bitter taste genetics—the relationship to tasting, liking, consumption and health. Food Funct. 2014;5(12):3040–54. https://doi.org/10.1039/C4FO00539B

.“)].

Although the mouth can detect only five tastes, it seems that the nasal chamber has the ability to perceive an unlimited number of chemical stimuli [[21](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR21 “Negoias S, et al. New ways to understand aroma perception. Food Chem. 2008;108(4):1247–54. https://doi.org/10.1016/j.foodchem.2007.08.030

.“)]. Aromatic molecules are introduced into the nasal canal through multiple ways, including breath, the act of chewing food, and the process of swallowing food [[22](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR22 “Hummel T, Livermore A. Intranasal chemosensory function of the trigeminal nerve and aspects of its relation to olfaction. Int Arch Occup Environ Health. 2002;75:305–13. https://doi.org/10.1007/s00420-002-0315-7

.“)]. Typically, food products contain odoriferous chemicals at low quantities, usually measured in milligrams per kilogram (mg/kg), or occasionally in micrograms per kilogram (µg/kg). The reason for this is that the olfactory system of humans is capable of detecting aroma-active chemicals even when they are present in very low quantities [23]. The “odor threshold” refers to the minimum concentration of a component in a certain medium that is necessary for it to be perceived as a distinct aroma. Hence, this measure is crucial for characterizing the scent components and their impact on the flavor of food [[24](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR24 “Buttery RG. Flavor chemistry and odor thresholds. In: Flavor chemistry: thirty years of progress. 1999, Springer;p. 353–365. https://doi.org/10.1007/978-1-4615-4693-1_30

“)]. The “taste threshold” refers to the concentration of substances that trigger the receptors in the mouth and provide the sensation of taste [[25](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR25 “Frank O, Ottinger H, Hofmann T. Characterization of an intense bitter-tasting 1 H, 4 H-quinolizinium-7-olate by application of the taste dilution analysis, a novel bioassay for the screening and identification of taste-active compounds in foods. J Agric Food Chem. 2001;49(1):231–8. https://doi.org/10.1021/jf0010073

.“)]. Nevertheless, determining the smell threshold is a complex task due to various elements that affect its value primarily the interactions between odorants and major components of food like carbohydrates, lipids, or proteins. These interactions have a significant impact on the binding of aromas and the release of chemicals into the surrounding air in different ways. As a result, it affects the value of the odor threshold.

Different factors, including substrate availability, salt, water activity, pH, and temperature influence the flavor of LAB-fermented products. Microbial metabolism can be regulated by these factors and produces crucial flavor compounds like sulfur-containing compounds, esters, hydrocarbons, terpenes, ketones, acids, aldehydes, alcohols, and others which give taste and aroma to fermented vegetables [[26](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR26 “Smid E, Kleerebezem M. Production of aroma compounds in lactic fermentations. Annu Rev Food Sci Technol. 2014;5:313–26. https://doi.org/10.1146/annurev-food-030713-092339

.“)]. LAB uses a variety of mechanisms to endure rapid environmental shifts and adverse conditions to preserve or enhance the flavor and quality of fermented goods [[27](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR27 “Hu Y, et al. Application of lactic acid bacteria for improving the quality of reduced-salt dry fermented sausage: texture, color, and flavor profiles. LWT. 2022;154:112723. https://doi.org/10.1016/j.lwt.2021.112723

.“)].

In LAB metabolism, temperature is a crucial factor. Most of the LAB strains grow best at the range of 30–45 °C. However, certain thermophilic strains, such as Streptococcus thermophilus and Lactobacillus acidophilus can survive at high temperatures like 45 °C. However, LABs experience thermal stress at temperatures outside of this range, especially at lower temperatures, which hinders their ability to develop and survive [[28](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR28 “Anumudu CK, Miri T, Onyeaka HJF. Multifunctional applications of lactic acid bacteria: enhancing safety, quality, and nutritional value in foods and fermented beverages. Foods. 2024;13(23):3714. https://doi.org/10.3390/foods13233714

.“)]. At high/intense temperatures, a sour taste is produced due to the accumulation of lactic acid. At low temperatures, cheesy/buttery taste is produced due to the accumulation of acetoin and diacetyl [[29](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR29 “Smit G, Smit BA, Engels JM. Flavour formation by lactic acid bacteria and biochemical flavour profiling of cheese products. FEMS Microbial Rev. 2005;29(3):591–610. https://doi.org/10.1016/j.fmrre.2005.04.002

.“)].

pH is also a crucial operational factor that has a significant impact on the product pattern and the functioning bacterial community [[30](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR30 “Yang Y, et al. Anaerobic propionic acid production via succinate pathway at extremely low pH. Chem Eng J. 2024;486:150190. https://doi.org/10.1016/j.cej.2024.150190

.“)]. The food matrix pH typically decreases due to LAB fermentation [[31](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR31 “Chen C, et al. Influence of 4 lactic acid bacteria on the flavor profile of fermented apple juice. Food Biosci. 2019;27:30–6. https://doi.org/10.1016/j.fbio.2018.11.006

.“)]. Lactic acid production reduces the food pH and prevents the microorganisms’ growth like L. monocytogenes and E. coli, which cannot survive in the altered low-pH environment. Furthermore, it significantly provides the bitter flavor that mostly fermented foods have [[28](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR28 “Anumudu CK, Miri T, Onyeaka HJF. Multifunctional applications of lactic acid bacteria: enhancing safety, quality, and nutritional value in foods and fermented beverages. Foods. 2024;13(23):3714. https://doi.org/10.3390/foods13233714

.“)]. Higher pH causes a distinct hammy sour flavor and a noticeable darkening or blackening which is a sign of over fermentation [[32](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR32 “Aprotosoaie AC, et al. Flavor chemistry of cocoa and cocoa products—an overview. Compr Rev Food Sci Food Saf. 2016;15(1):73–91. https://doi.org/10.1111/1541-4337.12180

.“)].

The salt concentration is also crucial in the metabolism of LAB for flavor formation. LAB grows efficiently in low salt concentrations and enhances fermentation while in high salt concentrations can inhibit LAB activity and ultimately minimize the flavor molecules production such as esters, ethanol, and acetic acid [[27](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR27 “Hu Y, et al. Application of lactic acid bacteria for improving the quality of reduced-salt dry fermented sausage: texture, color, and flavor profiles. LWT. 2022;154:112723. https://doi.org/10.1016/j.lwt.2021.112723

.“)].

Oxygen availability is another environmental characteristic that can affect LAB [[29](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR29 “Smit G, Smit BA, Engels JM. Flavour formation by lactic acid bacteria and biochemical flavour profiling of cheese products. FEMS Microbial Rev. 2005;29(3):591–610. https://doi.org/10.1016/j.fmrre.2005.04.002

.“)]. LABs are classified as obligate or facultative anaerobes [[33](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR33 “Gänzle MG. Lactic metabolism revisited: metabolism of lactic acid bacteria in food fermentations and food spoilage. Curr Opin Food Sci. 2015;2:106–17. https://doi.org/10.1016/j.cofs.2015.03.001

.“)]. LAB undergoes homo-lactic fermentation and produces lactate under strict anaerobic conditions and pyruvate metabolism occurs and produces acetate and ethanol under aerobic conditions [[34](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR34 “La GJF, Sciences N. The citrate metabolism in homo-and heterofermentative LAB: a selective means of becoming dominant over other microorganisms in complex ecosystems. 2014. http://www.scirp.org/journal/PaperInformation.aspx?PaperID=46158

“)]. In fermented vegetables, flavor balance occurs from sweetness to sourness due to these shifts. In short, flavor profile is largely characterized by different ecological factors affecting LAB activity. Desired sensory characteristics can be achieved controlling these environmental conditions on LAB.

Improvement of flavor formation

In fermented foods, several parameters, including substrate availability, salt, oxygen, water activity, pH, and temperature, affect the flavor development by lactic acid bacteria [[35](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR35 “Ardö Y. Flavour formation by amino acid catabolism. Biotechnol Adv. 2006;24(2):238–42. https://doi.org/10.1016/j.biotechadv.2005.11.005

.“)]. High temperature [[29](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR29 “Smit G, Smit BA, Engels JM. Flavour formation by lactic acid bacteria and biochemical flavour profiling of cheese products. FEMS Microbial Rev. 2005;29(3):591–610. https://doi.org/10.1016/j.fmrre.2005.04.002

.“)], low pH [[28](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR28 “Anumudu CK, Miri T, Onyeaka HJF. Multifunctional applications of lactic acid bacteria: enhancing safety, quality, and nutritional value in foods and fermented beverages. Foods. 2024;13(23):3714. https://doi.org/10.3390/foods13233714

.“)], and low salt levels [[27](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR27 “Hu Y, et al. Application of lactic acid bacteria for improving the quality of reduced-salt dry fermented sausage: texture, color, and flavor profiles. LWT. 2022;154:112723. https://doi.org/10.1016/j.lwt.2021.112723

.“)] enhance LAB fermentation and impart sour/bitter flavor which fermented foods usually have while low-temperature [[29](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR29 “Smit G, Smit BA, Engels JM. Flavour formation by lactic acid bacteria and biochemical flavour profiling of cheese products. FEMS Microbial Rev. 2005;29(3):591–610. https://doi.org/10.1016/j.fmrre.2005.04.002

.“)], high pH [[32](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR32 “Aprotosoaie AC, et al. Flavor chemistry of cocoa and cocoa products—an overview. Compr Rev Food Sci Food Saf. 2016;15(1):73–91. https://doi.org/10.1111/1541-4337.12180

.“)], and high salt levels [[27](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR27 “Hu Y, et al. Application of lactic acid bacteria for improving the quality of reduced-salt dry fermented sausage: texture, color, and flavor profiles. LWT. 2022;154:112723. https://doi.org/10.1016/j.lwt.2021.112723

.“)] lower the LAB activity and ultimately lower the production of flavor molecules. LAB employs many mechanisms to withstand adverse environmental conditions and immediate changes, thereby enhancing or preserving the taste and quality of fermented foods [[36](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR36 “Wu C, Huang J, Zhou R. Genomics of lactic acid bacteria: current status and potential applications. Crit Rev Microbiol. 2017;43(4):393–404. https://doi.org/10.1080/1040841X.2016.1179623

.“)]. Nevertheless, the fermentation settings typically remain fixed and are challenging to regulate, resulting in a lack of uniformity in the overall flavor quality of the product. The utilization of metabolic engineering and functional starter cultures has been employed as efficient methods to augment the formation of flavor, addressing this issue in contemporary large-scale production of fermented foods and preserving their inherent qualities [[37](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR37 “Devanthi PVP, Gkatzionis K. Soy sauce fermentation: microorganisms, aroma formation, and process modification. Food Res Int. 2019;120:364–74. https://doi.org/10.1016/j.foodres.2019.03.010

.“)]. Furthermore, metabolic engineering holds great promise for a variety of secondary volatile metabolites involved in altering floral aroma profiles and improving fruit quality [[39](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR39 “Abbas F, et al. Aroma components in horticultural crops: chemical diversity and usage of metabolic engineering for industrial applications. Plants. 2023;12(9):1748. https://doi.org/10.3390/plants12091748

.“)]. Significant advancements in these strategies have enormous potential and provide a conceptual and technical framework to expedite the development of novel metabolic enzymes and pathways [[40](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR40 “Sukumaran NP, et al. A Sense of Design: Pathway Unravelling and Rational Metabolic Flow Switching for the Production of Novel Flavor Materials. 2023: p. 47–62. https://doi.org/10.1002/9783527824816.ch3

“)].

In the food business, LAB is primarily utilized as a starter culture for a vast array of fermented vegetables, fruits, cereals, and dairy products. Additionally, by producing aroma components and acting as adjunct cultures. LAB enhances the nutritional value, texture, and flavor of fermented foods. To produce nutritional components, LAB also break down or produce exopolysaccharides, lipids, and proteins. It functions as probiotics, promotes therapeutic effects, and also acts as functional cultures [[38](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR38 “Bintsis TJAm. Lactic acid bacteria as starter cultures: an update in their metabolism and genetics. AIMS Microbiol. 2018;4(4):665. https://doi.org/10.3934/microbiol.2018.4.665

.“)]. Bacteriocins, aromatic compounds, polyols, organic acids, and Exopolysaccharides (EPS), belong to the widely recognized LAB properties that are beneficial to create functional starter cultures. In the food matrix, these cultures are released to improve their shelf life and affect health, aroma, flavor and texture [[13](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR13 “Hatti-Kaul R, et al. Lactic acid bacteria: from starter cultures to producers of chemicals. FEMS Microbiol Lett. 2018;365(20):fny213. https://doi.org/10.1093/femsle/fny213

.“)].

For more than 6000 years, LAB has been widely utilized to ferment plant-based meals including sauerkraut, kimchi, and sourdough bread. In the absence of refrigeration, their capacity to produce lactic acid has proven crucial in prolonging the lifespan of perishable items [[28](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR28 “Anumudu CK, Miri T, Onyeaka HJF. Multifunctional applications of lactic acid bacteria: enhancing safety, quality, and nutritional value in foods and fermented beverages. Foods. 2024;13(23):3714. https://doi.org/10.3390/foods13233714

.“)]. Starter cultures for vegetable production can be chosen according to how much carbon dioxide they produce. The excessive carbon dioxide content in olives and pickles can cause “bloaters” and lower product production. However, the generation of carbon dioxide in the fermentation of cabbage is advantageous as it helps create an anaerobic environment for the development of sauerkraut [[41](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR41 “Vinicius De Melo Pereira G, et al. A review of selection criteria for starter culture development in the food fermentation industry. Food Rev Int. 2020;36(2):135–67. https://doi.org/10.1080/87559129.2019.1630636

.“)]. LAB ferments kimchi at low temperatures, guaranteeing appropriate ripening and storage. During preservation the vegetables quality is preserved by the creation of organic acids from carbohydrates and the ensuing pH drop. Properly fermented kimchi has a unique savory blend of sour, spicy, hot, sweet, and fresh flavors. Enhancing kimchi’s sensory qualities, increasing its shelf life, and obtaining functional qualities and consistent quality are all goals of adding starting cultures [[42](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR42 “Lee M-E, et al. Starter cultures for kimchi fermentation. J Microbiol Biotechnol. 2015;25(5):559–68. https://doi.org/10.4014/jmb.1501.01019

.“)]. The most significant and prevalent microbe in the middle and later stages of kimchi fermentation is Lactobacillus plantarum. As a generally recognized safe (GRAS) microbe, Lactobacillus plantarum has been utilized as a probiotic strain and to ferment a wide range of foods including numerous vegetables [[43](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR43 “Yang S-J, et al. Antioxidant and immune-enhancing effects of probiotic Lactobacillus plantarum 200655 isolated from kimchi. Food Sci Biotechnol. 2019;28:491–9. https://doi.org/10.1007/s10068-018-0473-3

.“)].

Fermented vegetable products

Chinese cuisine has a strong connection to fermented vegetable products, with its origins dating third century B.C. [[44](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR44 “Caplice E, Fitzgerald GF. Food fermentations: role of microorganisms in food production and preservation. Int J Food Microbiol. 1999;50(1–2):131–49. https://doi.org/10.1016/S0168-1605(99)00082-3

.“)]. In China, the most known fermented vegetable products are Jiangxi yancai, Sauerkraut, Sichuan paocai, and Dongbei suancai [[45](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR45 “Guan Q, et al. Comparison of microbial communities and physiochemical characteristics of two traditionally fermented vegetables. Food Res Int. 2020;128:108755. https://doi.org/10.1016/j.foodres.2019.108755

.“), [46](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR46 “Xiao M, et al. Correlation between microbiota and flavours in fermentation of Chinese Sichuan Paocai. Food Res Int. 2018;114:123–32. https://doi.org/10.1016/j.foodres.2018.06.051

.“)]. Jiangxi yancai is a well-known traditional salted pickle that is highly popular in China, particularly in the eastern regions. It is prepared using various types of vegetables, which are thoroughly washed and then left to dry partially under sunlight for 5–6 h. Afterward, salt is added, and the semi-dried vegetables are then put in a jar with water to undergo natural fermentation for up to 8 days [[47](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR47 “Xiao M, et al. The microbial communities and flavour compounds of Jiangxi yancai, Sichuan paocai and Dongbei suancai: three major types of traditional Chinese fermented vegetables. LWT. 2020;121:108865. https://doi.org/10.1016/j.lwt.2019.108865

.“)]. Sauerkraut is a local dish that is widely consumed in China, especially in the northeast region. During the thirteenth century, the idea of fermenting cabbage was transferred from China to Europe, where the name sauerkraut was given to the final product [48]. Sauerkraut is made from fresh cabbage. First, the cabbage is cleaned with water, then cut and pasteurized for 1 min. Second, the pasteurized cabbage is mixed with a salt solution at a ratio of 1 g/100 g, followed by inoculation with lactic acid bacteria. Fermentation is then carried out at 18–20 °C for approximately 30 days [[49](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR49 “Yang X, Hu W, Xiu Z, Ji Y, Guan Y. Interactions between Leu. mesenteroides and L. plantarum in Chinese northeast sauerkraut. LWT. 2022;168:113901. https://doi.org/10.1016/j.lwt.2022.113901

.“)]. Sichuan paocai is a traditional Chinese fermented vegetable dish, specifically popular in the Sichuan region of southwestern China. With a history of thousands of years, it is typically prepared from different vegetables, such as radish, cabbage, ginger, and pepper. These vegetables are pretreated and then combined with a 6–8% (w/v) salt solution along with seasonings, such as chili and garlic. The mixture is then fermented at room temperature (20–25 °C) for up to 10 days in a glass jar with lactic acid bacteria under anaerobic fermentation [[46](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR46 “Xiao M, et al. Correlation between microbiota and flavours in fermentation of Chinese Sichuan Paocai. Food Res Int. 2018;114:123–32. https://doi.org/10.1016/j.foodres.2018.06.051

.“)]. Dongbei suancai is a pickled vegetable dish and another popular traditional fermented vegetable product from northern China [[50](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR50 “Liang HP, He Z, Wang XY, Song G, Chen HY, Lin XP, et al. Bacterial profiles and volatile flavor compounds in commercial Suancai with varying salt concentration from Northeastern China. Food Research International, 2020;137(12), Article 109384. https://doi.org/10.1016/j.foodres.2020.109384

“)]. It is typically produced through spontaneous fermentation, in which lactic acid bacteria develop naturally during the process. However, several studies have investigated the preparation of Dongbei suancai using inoculated lactic acid bacteria to accelerate fermentation. The complete preparation process of Dongbei suancai is described in the following articles [[51](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR51 “Wang C, Zhang S, Fang C, Han Y, Zhu S, Ban Z. Gamma irradiation inhibited non-enzymatic browning of Dongbei Suancai during storage. Food Biosci. 2023;55:102976. https://doi.org/10.1016/j.fbio.2023.102976

.“), [52](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR52 “Zhao Y, Zhao Z, Gao Y, Yang G, Liu X, Huang R, et al. Assessment of autochthonous lactic acid bacteria as starter culture for improving traditional Chinese Dongbei Suancai fermentation. Lwt. 2023;178:114615. https://doi.org/10.1016/j.lwt.2023.114615

.“)]. These four traditional Chinese fermented vegetable dishes are discussed further in (Fig. 1).

Fig. 1

A Map of China, which shows the regional consumption of different traditional Chinese fermented vegetable products

The primary species of lactic acid bacteria found in fermented vegetables are Lactococcus, Tetragenococcus, Weissella, Pediococcus, as well as Lactobacillus. In fermented vegetables, these microbial species are crucial to the development of flavors [[47](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR47 “Xiao M, et al. The microbial communities and flavour compounds of Jiangxi yancai, Sichuan paocai and Dongbei suancai: three major types of traditional Chinese fermented vegetables. LWT. 2020;121:108865. https://doi.org/10.1016/j.lwt.2019.108865

.“)]. During the fermentation of Sichuan paocai, [[45](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR45 “Guan Q, et al. Comparison of microbial communities and physiochemical characteristics of two traditionally fermented vegetables. Food Res Int. 2020;128:108755. https://doi.org/10.1016/j.foodres.2019.108755

.“), [46](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR46 “Xiao M, et al. Correlation between microbiota and flavours in fermentation of Chinese Sichuan Paocai. Food Res Int. 2018;114:123–32. https://doi.org/10.1016/j.foodres.2018.06.051

.“)] examined the changes in flavor components and microbial community. The findings indicated that the process of fermentation was primarily controlled by Lactobacillus, Leuconostoc, Staphylococcus, Streptococcus, and Pediococcus. The correlation study revealed that the bacterial impact on the development of flavor was greater than that of fungus. Lactobacillus showed a positive correlation with 3-methoxy-thiophene, ethyl ester, 2-butenoic acid, 1,2-propanediol diformate, 3-mercaptohexyl butanoate, formic acid, and lactic acid. Leuconostoc was found to be positively linked with lavandulyl acetate, 2,4-dimethylthiazole, dihexyl-3-methyl-ethylene oxide, and diamyl sulfite. In a study, the researchers similarly assessed the microbial populations in Jiangxi yancai, Sichuan paocai, and Dongbei suancai. They also made predictions about the functioning purpose of these bacteria and their connections to the flavor components [[47](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR47 “Xiao M, et al. The microbial communities and flavour compounds of Jiangxi yancai, Sichuan paocai and Dongbei suancai: three major types of traditional Chinese fermented vegetables. LWT. 2020;121:108865. https://doi.org/10.1016/j.lwt.2019.108865

.“)]. The findings revealed that Lactobacillus constituted a significant fraction of the species in all three analyzed products, and distinct variations in the bacterial community structure were observed across different fermented vegetables. The bacterial species P. pentosaceus, Lb. acetotolerans, and Lb. sakei were identified as the specific indicators for Jiangxi yancai, Sichuan paocai, and Dongbei suancai, respectively. Multiple Lactobacillus strains were strongly linked to over 20 flavor components. One of the bacteria, Lb. sakei, showed a positive correlation with volatile chemicals including (R)-3-hydroxybutyric acid, lactic acid, benzoic acid, and ethyl esters. The presence of Lb. acetotolerans was found to be associated with specific volatile chemicals, including lactic acid, 6-dien-3-ol, 3-methylhepta-1, terpinyl acetate, linalool, and sinapic acid [[53](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR53 “He W, Chung HY. Exploring core functional microbiota related with flavor compounds involved in the fermentation of a natural fermented plain sufu (Chinese fermented soybean curd). Food Microbiol. 2020;90:103408. https://doi.org/10.1016/j.fm.2019.103408

.“)]. Researchers [[54](#ref-CR54 “Liang H, et al. Effects of salt concentration on microbial diversity and volatile compounds during suancai fermentation. Food Microbiol. 2020;91:103537. https://doi.org/10.1016/j.fm.2020.103537

.“),[55](#ref-CR55 “Liu Z, et al. Comparison of the bacterial communities in home-made Nanfeng yancai with and without salt. Food Res Int. 2019;125:108509. https://doi.org/10.1016/j.foodres.2019.108509

.“),[56](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR56 “He Z, et al. Effects of different temperatures on bacterial diversity and volatile flavor compounds during the fermentation of suancai, a traditional fermented vegetable food from northeastern China. LWT. 2020;118:108773. https://doi.org/10.1016/j.lwt.2019.108773

.“)] examined in their studies that the volatile chemicals and bacterial species produced at different temperatures during suancai fermentation. Leuconostoc was the most abundant microorganism during fermentation at temperatures of 15 °C and 10 °C, but Lactococcus and Weissella were the prevailing species at temperatures of 25 °C and 20 °C. The bacteria Enterobacter, Psychrobacter, Brochothrix, Lactococcus, Acinetobacter, Pediococcus, Lactobacillus, and Pseudoalteromonas, were found to be directly associated with the volatile compounds production during fermentation. With 13 volatile chemicals, the main genus Lactobacillus showed a strong positive connection. Leuconostoc had a strong positive connection with many compounds including 3-phenylpropanol, 1-octanol, 2, 5-dimethylbenzaldehyde, cishept-4-enol, phenylethyl alcohol, linalool, and 1-hexanol. Lactococcus and Pediococcus had a favorable correlation with 1-hexanol and 2,4-di-tert-butylphenol. Pediococcus had a favorable correlation with 1,3-bis (1,1-dimethylethyl) benzene and (2-isothiocyanatoethyl) benzene.

These studies [[57](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR57 “Yang X, et al. Comparison of Northeast sauerkraut fermentation between single lactic acid bacteria strains and traditional fermentation. Food Res Int. 2020;137:109553. https://doi.org/10.1016/j.foodres.2020.109553

.“), [58](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR58 “Yang X, et al. Microbial community dynamics and metabolome changes during spontaneous fermentation of northeast sauerkraut from different households. Front Microbiol. 2020;11:1878. https://doi.org/10.3389/fmicb.2020.01878

.“)] were conducted to assess the metabolic and microbiological characteristics of northeast sauerkrauts. Instead of the white cabbage (*Brassica oleracea L. var. capitata *L.) used in European sauerkraut, these sauerkrauts are made using Chinese cabbage (*Brassica rapa *L. pekinensis, cv. Wombok). The initial study [[57](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR57 “Yang X, et al. Comparison of Northeast sauerkraut fermentation between single lactic acid bacteria strains and traditional fermentation. Food Res Int. 2020;137:109553. https://doi.org/10.1016/j.foodres.2020.109553

.“)] involved the isolation of LAB from typical northeast sauerkraut and the subsequent comparison of single starting cultures. A total of 99 volatile chemicals were tentatively identified after fermentation. These compounds include 4 lactones, 9 terpenes, 3 indoles, 7 sulfides, 5 nitriles, 2 hydrocarbons, 7 ketones, 13 aldehydes, 7 isothiocyanates, 23 esters, 9 alcohols, and 10 acids. The sauerkraut fermented with Lactobacillus plantarum had the highest concentration of esters, specifically isoamyl acetate, ethyl acetate, and ethyl lactate. On the other hand, sauerkraut inoculated with Lactobacillus paracasei had the highest number of lactones. The fermentation process, including Weissella cibaria and Leuconostoc mesenteroides, led to the production of ketones and acids [[57](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR57 “Yang X, et al. Comparison of Northeast sauerkraut fermentation between single lactic acid bacteria strains and traditional fermentation. Food Res Int. 2020;137:109553. https://doi.org/10.1016/j.foodres.2020.109553

.“)]. Table 1 presents a comparative analysis of the flavor profiles of fermented vegetable products, highlighting the differences resulting from specific microbial communities involved.

Responsible microbes for flavor formation in fermentation

As functional starter cultures, LAB are commonly employed to enhance the flavor of fermented foods [[59](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR59 “Dongmo SN, et al. Flavor of lactic acid fermented malt based beverages: current status and perspectives. Trends Food Sci Technol. 2016;54:37–51. https://doi.org/10.1016/j.tifs.2016.05.017

.“)]. LAB are widely acknowledged as the primary microbiota strains that exert strong influences on the characteristics of numerous fermented foods [[60](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR60 “Paterson A, Piggott JR. Flavour in sourdough breads: a review. Trends Food Sci Technol. 2006;17(10):557–66. https://doi.org/10.1016/j.tifs.2006.03.006

.“)]. The LAB group comprises 6 families of over 380 species in 40 genera. These bacteria are classified under the order Lactobacillus’s within the phylum Firmicutes. The primary lactic acid bacteria genera found in fermented foods are Weissella, Streptococcus, Pediococcus, Leuconostoc (Leu), Lactococcus (Lc), and Lactobacillus (Lb.) [[61](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR61 “Tamang JP, Watanabe K, Holzapfel WH. Diversity of microorganisms in global fermented foods and beverages. Front Microbiol. 2016;7:181961. https://doi.org/10.3389/fmicb.2016.00377

.“)]. Numerous microorganisms develop from the environment, equipment, starter cultures, and raw material throughout fermentation. Fermented foods contain microorganisms that can break down the biochemical components of raw materials, like carbohydrates, lipids, and proteins increasing their flavor and digestibility while adding nutritional and pharmacological benefits [[62](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR62 “Hu Y, et al. Role of lactic acid bacteria in flavor development in traditional Chinese fermented foods: a review. Crit Rev Food Sci Nutr. 2022;62(10):2741–55. https://doi.org/10.1080/10408398.2020.1858269

.“)]. In addition to being the source of endogenous enzymes and adventitious microbes, raw materials give substrates to microorganisms. Processing conditions include the careful addition of exogenous enzymes and microbial cultures. The interactions taking place in fermented foods between microbes, products and processing conditions are important for flavor development. Influencing LAB growth, lysis or metabolic activity in foods, as well as providing suitable substrates and conditions, is necessary for aroma-forming reactions. In food ecosystems, the expression of LAB’s flavor-related activities is influenced by biotic and abiotic variables [[15](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR15 “Thierry A, et al. Production of flavor compounds by lactic acid bacteria in fermented foods. Biotechnology of lactic acid bacteria: novel applications, 2015: p. 314–340. https://doi.org/10.1002/9781118868386.ch19

“)].

The primary role of LAB in fermented foods is to convert carbohydrates into lactic acid, which effectively acidifies the food matrix and enhances the shelf life and products microbiological safety. Additionally, in fermented foods, most lactic acid bacteria (LAB) can benefit the flavor formation [[14](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR14 “De Vuyst L, Neysens P. The sourdough microflora: biodiversity and metabolic interactions. Trends Food Sci Technol. 2005;16(1–3):43–56. https://doi.org/10.1016/j.tifs.2004.02.012

.“), [15](https://journalofethnicfoods.biomedcentral.com/articles/10.1186/s42779-025-00295-1#ref-CR15 “Thierry A, et al. Production of flavor compounds by lactic acid bacteria in fermented foods. Biotechnology of lactic acid bacteria: novel applications, 2