Microbiological Dimensions Symbiotic Culture of Bacteria and Yeast (SCOBY) and Functional Properties of Kombucha Tea Fermented Drink
2026 年 14 巻 1 号 p. 68-91
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2026 年 14 巻 1 号 p. 68-91
Kombucha is a fermented tea beverage whose global popularity is driven by its distinctive flavor and purported health benefits. This review provides a comprehensive analysis of its production, microbial ecosystem, and nutritional profile, distinguishing between consumer perception and scientific evidence for its functional properties. We examine the critical challenges in production and safety, including microbial contamination, SCOBY variability, and controlling acetic acid and ethanol levels. The analysis further addresses the regulatory landscape governing alcohol content and health claims, as well as emerging market trends. Finally, we identify key future directions, underscoring the necessity for technological innovation, robust clinical validation, and enhanced quality control to align the kombucha industry with evolving consumer and regulatory standards.
Kombucha is a fermented, sweetened tea beverage produced by a symbiotic culture of bacteria and yeast (SCOBY). With traditional origins in Northeast Asia circa 220 B.C., it has evolved from a folk remedy into a globally commercialized product [1, 2]. Its rise in popularity is fueled by consumer demand for natural, functional beverages and a distinctive sensory profile derived from its complex microbial metabolism [3, 4]. The fermentation, driven by the SCOBY, involves yeasts converting sugars to ethanol, which acetic acid bacteria then oxidize into organic acids such as acetic, gluconic, and lactic acid [5]. This process yields a spectrum of bioactive compounds, including polyphenol derivatives, vitamins, and various volatile metabolites, which contribute to its characteristic sweet-sour taste and purported health benefits [6, 7].
Despite its commercial success—with the global market projected to reach USD 3.5–5 billion by 2024—scientific validation of its health claims lags behind public perception [3, 8]. Evidence for antioxidant, detoxifying, and probiotic effects remains largely preliminary, based predominantly on in vitro and animal models, with robust human clinical data being limited and inconsistent [7, 8].
This review provides a comprehensive analysis of kombucha, examining its microbial ecology, fermentation dynamics, nutritional profile, and the scientific evidence underpinning its functional properties. It further addresses the critical production challenges, regulatory frameworks, and future directions necessary to align this ancient beverage with modern scientific and market standards.
Kombucha is a traditional fermented tea whose origins are generally traced to Northeast Asia, most likely China, where early forms of tea fermentation were practiced around 200 BCE [1, 2]. Although historical descriptions often refer to kombucha as the “tea of immortality”, such expressions reflect cultural beliefs rather than verifiable evidence. The beverage later spread to Korea and Japan, where it became associated with traditional health practices. Notably, the commonly cited story of a Korean physician named “Dr. Kombu” introducing kombucha to Japan lacks historical verification and is regarded as anecdotal [9, 10]. Terminological confusion has also contributed to misconceptions about kombucha’s origin. In Japan, kombucha typically refers to konbu-cha, a kelp-based infusion unrelated to the fermented tea beverage. The fermented product discussed in modern scientific literature was historically known as kōcha kinoko (“red tea mushroom”), a term that references the tea substrate and the gelatinous microbial culture, or SCOBY, used in its production [2, 9, 10].
| Country/Region | Approx. Introduction | Peak Popularity | Current Status | References |
| Japan | ~1970s (introduced via health food trends) | Mid–1970s to early 1980s (“tea fungus” boom) | Rarely consumed today; overshadowed by konbu-cha (kelp tea) | [11] |
| Russia/Eastern Europe | Early 20th century (documented in Russia, Poland, Germany) | 1920s–1940s (home fermentation widespread) | Still consumed in some households; less common commercially | [13, 14] |
| Germany | Early 20th century (linked to Russian spread) | 1920s–1930s | Small niche market today | [11] |
| United States | First introduced mid–20th century; resurgence in 1990s | 2010s (major commercial expansion, functional beverage trend) | Large and growing market, significant commercial production | [15, 16] |
| Western Europe (e.g., UK, France) | Spread in late 20th century | 2010s (parallel to U.S. growth) | Expanding but smaller than U.S.; artisanal and commercial brands increasing | [15] |
| China | Believed to have been consumed historically, but documentation sparse | Localized/traditional use, not widespread | Minimal presence compared to tea culture; low commercial market | [11] |
| Australia | Late 20th century (via health food movements) | 2010s (wellness trend, artisanal brands) | Expanding niche market | [13] |
Kombucha entered Eastern Europe in the early 20th century, where it became known in Russia as “tea mushroom” (čajnyj grib). It was commonly home-brewed using a symbiotic culture of bacteria and yeast (SCOBY) in sweetened tea [11, 12]. Its popularity expanded to Germany and other parts of Europe, although shortages of tea and sugar during World War II temporarily reduced its prevalence (Table 1). Interest resurged in the 1960s during broader movements favoring natural remedies and fermented foods [9, 11, 12].
The modern global expansion of kombucha began in the United States in the 1990s. Commercialization, combined with increased consumer interest in probiotics and functional beverages, transformed kombucha from a niche homemade preparation into a widely marketed product available in diverse formulations. Scientific attention has similarly increased, with studies reporting antioxidant activity, potential digestive benefits, and antimicrobial properties, although definitive clinical evidence remains limited and continues to develop [3, 11]. Today, kombucha is produced both commercially and through home fermentation, supported by widespread sharing of SCOBY cultures and recipes. Its contemporary relevance lies not in anecdotal historical claims but in its established microbiological characteristics, fermentation dynamics, and potential functional properties—core aspects that form the scientific basis for current research and applications [17, 18].
Kombucha is produced by fermenting sweetened tea—typically black or green—with a SCOBY (Figure 1). Sucrose serves as the primary carbon source, which yeasts hydrolyze into glucose and fructose, which are then converted to ethanol. Acetic acid bacteria subsequently oxidize ethanol to acetic acid and other organic acids [9, 19]. This microbial succession generates diverse bioactive compounds—including vitamins and organic acids—while reducing sugar content [20, 21]. Certain SCOBY consortia may also include lactic acid bacteria, further influencing acidity and flavor [22, 23].
Key steps include: (a) Tea leaves, the raw material. (b) Brewing leaves in hot water. (c) Addition of granulated sugar. (d) Cooling the sweetened tea to room temperature and mixing with a kombucha starter culture. (e) Inoculation with a SCOBY. (f) Covering the vessel with a breathable cloth. (g) Fermentation at room temperature for 7-12 days. (h) Harvesting the pellicle (SCOBY) from the tea surface. (i) Filtering the fermented liquid. (j) Storage of the final product in an airtight bottle under refrigeration. (Source: self-documentation)
The SCOBY, a gelatinous cellulose-based biofilm, hosts this microbial community. As shown in Figure 2, production involves dissolving sucrose in freshly steeped tea. After cooling, the sweetened tea is inoculated with the SCOBY and starter liquid from a previous batch. The vessel is covered with a breathable cloth and fermented for 7–14 days, depending on temperature and desired sensory characteristics [19]. The final beverage’s composition and sensory properties are determined by the interplay between microbial activity and key parameters, including sugar concentration, temperature, pH, and fermentation time. Consequently, maintaining hygienic conditions and implementing quality control are essential for ensuring product safety, consistency, and consumer acceptability [24]. Kombucha fermentation proceeds through two principal stages. During primary fermentation, yeasts hydrolyze sucrose into glucose and fructose, which are subsequently converted into ethanol and carbon dioxide [20]. Concurrently, acetic acid bacteria oxidize the ethanol into acetic acid and other organic acids, lowering the pH and imparting the characteristic tart flavor. An optional secondary fermentation in sealed bottles allows trapped CO₂ to generate effervescence. This stage also facilitates further flavor development, often enhanced by adding fruits, herbs, or spices [25].
The process relies on a dynamic symbiosis between yeasts and bacteria (Table 2). Yeasts initially dominate, producing ethanol, which then stimulates the activity of acetic acid bacteria. These bacteria convert ethanol to acids, further acidifying the environment. Lactic acid bacteria, when present, also contribute to the final acidity and flavor profile [26]. This delicate balance is critical; its disruption can yield a product that is overly alcoholic, excessively acidic, or spoiled [21]. Maintaining a stable SCOBY consortium is therefore essential for product consistency and quality [22].
Sucrose, the predominant carbon source, is favored for its cost and availability. It is hydrolyzed to provide glucose and fructose for microbial metabolism, with an optimal concentration typically between 5 and 10% (w/v) [11, 23]. The biochemical pathway involves yeast glycolysis, where glucose is converted to pyruvate. Pyruvate is then decarboxylated to acetaldehyde and CO₂, and acetaldehyde is subsequently reduced to ethanol by alcohol dehydrogenase [27, 28].
| Sample | Research techniques | Fermentation isolate | References |
|---|---|---|---|
| Prickly Pear-Based Kombucha | Kombucha starter mixed with prickly pear with various sucrose concentrations and fermentation times | Yeast species Brettanomyces bruxellensis and Saccharomyces cerevisiae, as well as acetic acid bacteria (AAB) such as Komagataeibacter pomaceri and Komagataeibacter rhaeticus | [29] |
| Ganoderma lucidum | Kombucha infused with Ganoderma lucidum and green tea from Camellia sinensis (L.) kuntze | Commercial (generally consists of Acetobacter xylinum, Gluconobacter, S. cerevisiae) | [30] |
| Sea buckthorn | The kombucha starter was mixed with green tea and sea buckthorn, and the non-fermented and fermented samples were then compared. | Commercial | [31] |
| Dried pineapple peels and cores | Kombucha starter mixed with dried pineapple peels and cores with various sugar concentrations and fermentation times | Predominant bacteria were Acetobacter, Komagataeibacter, and Bacillus, while the yeast was Dekkera | [32] |
| Cascara (Coffea canephora Pierre ex A. Froehner) | Kombucha starter is mixed with cascara (Coffea canephora Pierre ex A. Froehner) with different fermentation times. | The bacterial group included Acetobacter xylinum, while yeast microorganisms from the genera Brettanomyces, Zygosaccharomycetes and Saccharomyces | [33] |
| Green tea, black tea, white tea (Camellia sinensis) | Kombucha starters are mixed with green, black, and white tea and fermented for varying lengths of time. | Commercial (generally consists of Acetobacter xylinum, Gluconobacter, S. cerevisiae) | [34] |
| Oolong tea (Camellia sinensis), Royal lotus pollen (Nelumbo nucifera), Butterfly pea flower (Clitoria ternatea) | Kombucha starter mixed with Oolong tea (Camellia sinensis), compared to Kombucha starter mixed with Royal lotus pollen (Nelumbo nucifera) and Kombucha starter mixed with Butterfly pea flower (Clitoria ternatea), with different fermentation times. | It contained yeast and acetic acid bacteria that play a role in kombucha fermentation | [35] |
| Cocoa honey | Kombucha starter mixed with cocoa honey with various fermentation times. | Commercial (generally consists of Acetobacter xylinum, Gluconobacter, S. cerevisiae) | [36] |
| Black tea (Camellia sinensis L.), roselle (Hibiscus sabdariffa L.) | Kombucha starter mixed with black tea (Camellia sinensis L.) and roselle (Hibiscus sabdariffa L.) with various concentration ratios of black tea and roselle and various fermentation times. | Bacterium Acetobacter pasteurianus AJ605 and the yeast Zygosaccharomyces bailii YN403 | [37] |
| Oolong tea kombucha, kitchen mint kombucha, Liquid starter, dan Cellulose starter | Kombucha starter mixed with oolong tea kombucha, kitchen mint kombucha, Liquid starter, and Cellulose starter, with various concentration ratios of oolong tea kombucha and kitchen mint kombucha and different fermentation times. | Contained yeast and acetic acid bacteria that play a role in kombucha fermentation | [38] |
Acetic acid bacteria oxidize fermentation-derived ethanol under aerobic conditions to support cell growth and produce acetic acid [39]. This process begins with ethanol oxidation to acetaldehyde via alcohol dehydrogenase, followed by further oxidation to acetyl-CoA by aldehyde dehydrogenase. Phosphotransacetylase then converts acetyl-CoA to acetyl phosphate, which acetate kinase dephosphorylates to yield acetic acid [27, 28].
Kombucha fermentation is governed by multiple factors: substrate type, SCOBY microbial composition, and environmental conditions such as temperature, pH, oxygen availability, and duration. Temperature critically influences microbial growth and metabolism, with an optimum typically between 20 and 30 °C [11]. Within this range, microbial activity is maximized, enhancing the production of beneficial compounds. For instance, temperature fluctuations significantly affect antioxidant activity by stimulating phenolic compound synthesis [40], while higher temperatures increase vitamin C and organic acid production [41].
Fermentation proceeds most efficiently between 21–29 °C; deviations can suppress desired microbes or promote contaminants. pH is equally critical, as it governs organic acid formation and modulates microbial activity. It also influences the final product's antioxidant properties [40]. The pH typically declines to 3.5–4.5, a range that inhibits pathogens and directs metabolic flux. Fermentation should ideally conclude once total acidity reaches ~4.2 to achieve the desired sour profile [42, 43]. As an aerobic process, kombucha fermentation requires sufficient oxygen for acetic acid bacteria to oxidize ethanol [44]. The tea substrate also modulates microbial dynamics; black tea, richer in nitrogenous compounds and tannins, supports more robust microbial growth than green tea, which imparts a distinct flavor [45].
Sugar type and concentration significantly impact microbial growth and flavor. While sucrose is standard, alternative sweeteners can impede fermentation [46]. Varying sugar concentrations alter the chemical profile; for example, 7.5% and 10% sucrose yielded antioxidant activities of 6.18 mg/L and 6.23 mg/L, respectively, while 20% sucrose reduced activity to 5.49 mg/L [47]. Similarly, a 10% sugar concentration in starfruit tea kombucha produced the lowest IC50 value, indicating the highest antioxidant potency [48]. Careful selection of sugar type and concentration can thus enhance the yield of bioactive compounds.
Fermentation duration, typically 7–14 days, determines the biochemical, sensory, and microbial properties. Antioxidant activity often increases during the first week as phytochemicals biotransform into polyphenols [49]. A 9-day fermentation can inhibit E. coli, S. aureus, and A. tumefaciens; extending this to 14 days suppresses additional pathogens like Shigella sonnei and Salmonella species [50]. Sensorily, a 6–10-day fermentation yields a fruity taste, while prolonged fermentation produces a vinegar-like flavor [15]. The FDA Model Food Code recommends not exceeding 10 days to ensure safety, as extended fermentation can lead to excessive organic acid accumulation and increased cytotoxicity, as observed in a 14-day versus a 28-day brew [51].
Strict hygiene is essential to prevent contamination, which can cause unsafe levels of acetic acid, elevated ethanol, or pathogen growth [52]. Although kombucha is noted for its probiotic and antioxidant benefits, improper fermentation poses risks [21]. Controlling these parameters ensures product safety and quality [53]. Further research into optimal production methods will continue to enhance both the safety and health appeal of kombucha.
The SCOBY consortium comprises acetic acid bacteria (e.g., Komagataeibacter, Acetobacter, Gluconacetobacter), lactic acid bacteria (e.g., Lactobacillus, Lactococcus), and yeasts (e.g., Saccharomyces, Zygosaccharomyces, Brettanomyces). This multi-species community collectively generates the characteristic acidity and aroma of kombucha over the typical 7- to 14-day fermentation period [24, 54]. Accordingly, Lee et al. [55] identified the phyla Proteobacteria and Firmicutes as dominant in the microbial communities of two commercial Korean kombuchas.
Kombucha yeast species, including Saccharomyces cerevisiae, Brettanomyces, and Candida, initiate fermentation by converting sugars (glucose and fructose) into ethanol and carbon dioxide [56]. Acetic acid bacteria (AAB), primarily Acetobacter and Gluconacetobacter, then oxidize this ethanol into acetic acid, imparting the characteristic sour taste. AAB also generates other organic acids, like gluconic and glucuronic acids, which contribute to the beverage's purported detoxifying properties [57]. Lactic acid bacteria (LAB), such as Lactobacillus and Leuconostoc, further enhance the flavor profile by producing lactic acid, potentially offering probiotic benefits for gut health [9, 58].
The microbial community in kombucha is primarily composed of yeasts, acetic acid bacteria (AAB), and, in some cases, lactic acid bacteria (LAB), which coexist within the symbiotic culture of bacteria and yeast (SCOBY) [59]. As a result, kombucha fermentation yields numerous bioactive compounds, many of which are believed to offer health benefits. Yeasts hydrolyze sucrose into glucose and fructose and ferment these sugars into ethanol and carbon dioxide, while AAB subsequently oxidize ethanol into acetic acid [22]. In addition to acetic acid, other metabolites are formed, including glucuronic acid, which is suggested to contribute to detoxification, although this effect has not been conclusively demonstrated in humans [22]. Lactic acid bacteria may contribute to gut health, but direct evidence from controlled human studies remains limited. To ensure accuracy in terminology, kombucha is more appropriately described as containing live microorganisms (including lactic acid bacteria), whose presence and activity can influence acidity, flavor development, and overall fermentation dynamics, rather than being classified as containing probiotics unless specific validated strains with clinically proven benefits are identified [57]. The nomenclature follows recent taxonomic updates, distinguishing Komagataeibacter from Gluconobacter (Table 3). Komagataeibacter xylinus (formerly Gluconacetobacter xylinus), meanwhile, is a distinct but related acetic acid bacterium.
| Study (year) | Region/samples (typical) | Method (marker/approach) | Main bacterial genera reported | Main yeast genera reported | Key note/relevance |
| [60] 2015 | Multiple (laboratory/experimental SCOBYs) | 16S rRNA metabarcoding; culture isolation | Komagataeibacter xylinus, Acetobacter, Gluconobacter (core taxa) | Brettanomyces, Zygosaccharomyces, Saccharomyces | Early metabarcoding shows a flexible community under different conditions. |
| [61] 2021 | Commercial North American SCOBYs | 16S & ITS amplicon sequencing (commercial brewers) | Komagataeibacter xylinus, Acetobacter dominant; variable minor LAB | Zygosaccharomyces, Brettanomyces, Saccharomyces; differences among commercial archetypes | Demonstrates “archetypes” used by North American brewers |
| [62] 2020 | Samples collected in Turkey (commercial & home) | Whole metagenome sequencing (WMS) + 16S/ITS | Komagataeibacter xylinus, Acetobacter; notable presence of LAB in some samples | Saccharomyces, Zygosaccharomyces; sample-dependent variation | WMS confirms taxa and gives functional insight. |
| [63] 2024 | SCOBYs from five regions (multi-region comparison) | Amplicon sequencing + metabolite profiling | Core Komagataeibacter xylinus across regions; regional differences in Gluconobacter and LAB | Regionally variable yeast composition; correlated with volatile profiles | Direct multi-region starter comparison (SCOBY selection) |
| [64] 2024 | SCOBYs from markets in Netherlands, USA, China, Iran | Isolation + 16S sequencing / characterization of cellulose-producers | Diverse Acetobacteraceae (Komagataeibacter xylinus and related cellulose producers) | — (study focused on bacteria) | Illustrates the global diversity of cellulose producers within SCOBYs. |
| [65] 2025 | Broad survey / meta-analysis (global literature) | Systematic survey / comparative meta-analysis of published datasets | Confirms a stable core (Komagataeibacter xylinus and Acetobacter) but reports regional shifts in secondary taxa. | Confirms common yeast groups; documents gaps in geographic sampling | Useful recent global overview and identification of under-sampled regions |
The fermentation process elevates concentrations of B vitamins (B1, B2, B6, and B12) and polyphenolic antioxidants, which are associated with enhanced immune function and reduced inflammation [66]. Organic acids, including acetic, gluconic, and glucuronic acids—may contribute to detoxification by binding to toxins and facilitating their excretion [57]. Collectively, these fermentation-derived bioactive compounds are implicated in kombucha's putative antioxidative and detoxifying properties, thereby supporting its role in promoting overall health [57]. The balance among these microbial groups, together with environmental factors such as temperature, pH, oxygen availability, and sugar concentration, shapes both the chemical composition and sensory qualities of the final beverage [66]. Understanding these interactions is essential for optimizing fermentation and ensuring product quality [67]. Representative comparative/regional SCOBY microbiome studies are shown in Table 3.
Time-course analysis is critical for elucidating the dynamic microbial interactions and metabolite transformations that underpin kombucha fermentation [57]. In contrast to endpoint measurements, temporal data capture microbial succession and sequential metabolic shifts, providing a mechanistic basis for understanding fermentation control and product quality. Across studies, kombucha fermentation exhibits a broadly consistent successional pattern [59]. Early fermentation is typically dominated by yeasts, which hydrolyze sucrose and produce ethanol and CO₂, initiating a moderate decline in pH. During the mid-fermentation stage, acetic acid bacteria (AAB), particularly Komagataeibacter and Acetobacter spp., increase in abundance and oxidize ethanol to acetic acid, accompanied by gluconic acid formation and accelerated acidification [57, 59]. Lactic acid bacteria may co-occur and contribute to lactic acid production, although their abundance and persistence vary considerably. In later stages, AAB often dominate, ethanol levels decrease, total acidity increases, and cellulose and secondary metabolites such as polysaccharides and volatile esters accumulate [57, 66]. Despite these shared trends, substantial variability exists among studies in the timing and magnitude of microbial and metabolite changes. Differences in tea matrix, sugar concentration, fermentation temperature, oxygen availability, and starter culture composition strongly influence microbial succession and metabolic outputs [57, 67]. Strain-level diversity further contributes to divergent fermentation trajectories. Overall, time-resolved analyses provide essential insight into microbial synergy and metabolite dynamics in kombucha fermentation, while highlighting both conserved patterns and context-dependent variability inherent to this complex microbial ecosystem.
The chemical composition of kombucha (Table 4) varies significantly with the tea base, fermentation duration, and the specific microbial constitution of the SCOBY. These parameters collectively determine the final concentrations of beneficial organic acids, vitamins, and trace minerals, resulting in a beverage that is generally low in calories, sugar, and alcohol [39].
| Sample | Ash content | Water content | Carbohydrate | Protein | Fat | References |
|---|---|---|---|---|---|---|
| kombucha 10% with low-fat milk | 0.66±0.020% | - | - | 3.5±0.021% | 1±0.025% | [68] |
| Kombucha 15% with low-fat milk | 0.63±0.018% | - | - | 3.4±0.028% | 1±0.019% | |
| Kombucha 20% with low-fat milk | 0.62±0.018% | - | - | 3.0±0.018% | 1±0.019% | |
| Kombucha 10% with medium-fat milk | 0.63±0.020% | - | - | 3.6±0.026% | 2.2±0.042% | |
| Kombucha 15% with medium-fat milk | 0.62±0.016% | - | - | 3.3±0.021% | 1.9±0.036% | |
| Kombucha 20% with medium-fat milk | 0.60±0.016% | - | - | 3.0±0.022% | 1.8±0.032% | [68] |
| Kombucha telang flower (per 100 ml) | 0.02% | 70.62% | 29.37 g | 0.04 g | 0.02 g | [69] |
| Kombucha flakes (per 100 g) | - | - | 90.3 g | 0.67 g | 0.2 g | [70] |
| Kombucha tea | 0.11 ± 0.005% | 95.36 ± 0.155% | 4.51 ± 0.202% | 0.03 ± 0.047% | 0.00 ± 0.000% | [71] |
| Kombucha noni | 0.30 ±0.047% | 94.07 ± 0.042% | 5.50 ± 0.063% | 0.08 ±0.002% | 0.04 ± 0.001% | |
| Kombucha soursop | 0.52 ± 0.093% | 92.63 ± 0.088% | 6.60 ± 0.098% | 0.11 ± 0.045% | 0.16 ± 0.037% | |
| Kombucha pineapple | 0.23 ± 0.035% | 92.28 ± 0.098% | 7.31 ± 0.155% | 0.11 ± 0.050% | 0.08 ± 0.002% | |
| Kombucha tea fungus 7th fermentation day | 8.50±0.51 g/kg dry matter | 96.39±1.04% | - | 121.50±1.15 g/kg dry matter | 18.10±0.56 g/kg dry matter | [72] |
| Kombucha tea fungus 14th fermentation day | 29.20±0.66 g/kg dry matter | 97.38±0.91% | - | 184.10±1.63 g/kg dry matter | 47.10±0.49 g/kg dry matter | |
| Kombucha tea fungus 21st fermentation day | 39.70±1.21 g/kg dry matter | 97.35±0.87% | - | 231.10±0.98 g/kg dry matter | 54.30±0.61 g/kg dry matter | |
| Kombucha black tea normal | 0.3442 ± 0.0123% | 91.6120 ± 0.2947% | 8.0543 ± 0.2345% | 0.0028 ± 0.0330% | - | [73] |
| Kombucha black tea cold shock | 0.2387 ± 0.0316% | 95.7191 ± 0.7084% | 4.0596 ± 0.7043% | 0.0175 ± 0.0111% | - | |
| Kombucha black tea pasteurisation | 0.2469 ± 0.0189% | 95.0568 ± 0.5289% | 4.7142 ± 0.5208% | 0.0179 ± 0.0108% | - | |
| Kombucha black tea yeast removal | 0.2405 ± 0.0435% | 95.1808 ± 0.0722% | 4.5661 ± 0.0112% | 0.0145 ± 0.0137% | - | |
| Kombucha Strawberry | - | - | 73.11 ± 1.23 mg/mL | 8.66 ± 0.08 µg/mL | - | [74] |
| Kombucha truffles (Tuber melanosporum) | - | - | 4.1-6.5% | < 31.0 µg/mL | - | [75] |
| Kombucha truffles (Tuber aestivum) | - | - | 2.9-4.8% | < 36.4 µg/mL | - | |
| Kombucha tea | - | - | 8.5 g/100 g | < 0.4g/100 g | < 0.1 g/100 g | [76] |
| kombucha gac, mango, 70 g sugar | - | - | 5.8 % | <0.2 | ND (<0.2) | [77] |
| Kombucha gac, mango, 80 g sugar | - | - | 6.4 % | ND (<0.2) | ND (<0.2) | |
| kombucha gac, mango, 100 g sugar | - | - | 6.9 % | ND (<0.2) | ND (<0.2) |
The nutritional profile of kombucha depends on the substrate, microbial composition, and fermentation conditions, which together influence sugar utilization and the generation of organic acids and other metabolites. In terms of energy content, most commercial kombucha products contain approximately 10–25 kcal (42–105 kJ) per 100 mL, equivalent to ~24–60 kcal per 240 mL serving. Values as high as 50 kcal per 8 oz (240 mL) are uncommon and generally reflect specific formulations with higher residual sugar content [68, 69, 70].
Carbohydrates in the sweetened tea are metabolized primarily by yeasts into ethanol and carbon dioxide. Acetic acid bacteria subsequently oxidized ethanol into acetic acid and gluconic acid, while lactic acid bacteria, when present, may also contribute modestly to acid production. The concentrations of these organic acids can vary considerably depending on fermentation time and conditions, with acetic acid typically reaching ~5–10 g/L, gluconic acid up to ~10–40 g/L, and glucuronic acid ~0.1–2 g/L. These compounds, along with vitamins, amino acids, and polyphenol derivatives from tea, shape the nutritional and functional profile of the beverage [68, 69, 70, 71].
Several health-related properties have been proposed for kombucha’s metabolites, but direct evidence from controlled human clinical studies remains limited. For example, glucuronic acid is suggested to play a role in detoxification, although this effect has not been conclusively demonstrated. Lactic acid may support beneficial gut microbiota, but this remains to be confirmed in human studies. Gluconic acid has been proposed to support immune function, although its potential role in this regard remains under investigation. Thus, while kombucha contains diverse bioactive compounds, its health-related benefits should be considered as potential rather than established [70, 71, 72].
Kombucha’s chemical profile is complex, comprising residual sugars (sucrose, glucose, fructose), a suite of organic acids (e.g., acetate, gluconate, lactate), and trace amounts of amino acids, vitamins (B1, B2, B6, B12, C), minerals (e.g., copper, iron, zinc), and other metabolites [66]. The synergistic interactions among these compounds define the beverage's characteristic taste, aroma, and purported health benefits, underscoring the need for precise fermentation control to achieve sensory and chemical profiles.
Ethanol dynamics during fermentation are governed by microbial succession. Yeasts initially drive their production, but acetic acid bacteria subsequently oxidize it to acetic acid, causing the alcohol concentration to peak and then decline [44]. In accordance with Food Standards Australia New Zealand [78], kombucha marketed as a non-alcoholic beverage must not exceed 0.5% (v/v) ethanol (Table 5).
| Country/region | Regulatory threshold/classification for “non-alcoholic / non-liquor” beverage | Typical kombucha alcohol range (v/v %) — context | References |
| United States (TTB / FDA) | 0.5% ABV is the commonly used legal threshold for labelling and taxation (kombucha ≥0.5% ABV falls under beverage-alcohol rules). | Many commercial kombuchas are formulated <0.5% ABV; “hard kombucha” products exceed this. | [79] |
| European Union / selected Member States (industry guidance) | No single EU-wide numeric definition for “non-alcoholic”; some member states/industry practice use ≤1.2% ABV for “low-alcohol” or adopt national thresholds for “alcohol-free”/“non-alcoholic” labelling. | Typical commercial ranges ~0.1–1.5% ABV; some products exceed 1% during shelf life. | [80] |
| United Kingdom | “Alcohol-free” is defined as ≤0.05% ABV; “low-alcohol” is often ≤1.2% ABV under recent guidance/consultation. | Commercial kombucha usually has an ABV >0.05% and is commonly reported as <0.5%; monitoring and labelling guidance is recommended. | [81] |
| Australia / New Zealand (FSANZ & state regs) | FSANZ / Food Standards Code: brewed/fermented soft drinks must declare alcohol if ≥0.5% ABV; beverages ≥1.15% ABV may be treated as liquor in some jurisdictions (labelling, licence, pregnancy warning). | National surveys found many kombucha samples >0.5% ABV; some >1.15% ABV — shelf life increases can push ABV higher. | [82] |
| Canada | Alcoholic beverage labelling rules require declaration of alcohol content; provincial tolerances apply (Canadian jurisdictions commonly monitor 0.5–1.1% thresholds depending on context). |
Many commercial kombuchas marketed as non-alcoholic aim for <0.5% ABV; some studies report non-complianc e. |
[83] |
| Brazil | Brazil introduced kombucha-specific labelling guidance: non-alcoholic kombucha may be labelled with statements such as “may contain up to 0.5% v/v”, and alcohol strength declarations are required on the main panel. | Brazilian surveys and legislation commonly use 0.5% ABV as a practical non-alcoholic threshold for kombucha. | [84] |
| China | National beverage standard(s) indicate that products with an alcohol mass fraction ≤0.5% are considered within the non-alcoholic beverage categories for general beverage standards. | Many commercial products sold as non-alcoholic are targeted to ≤0.5% ABV; enforcement and regional rules apply. | [85] |
| Indonesia (BPOM / national regs) | BPOM and related Indonesian regulations control the sale/labelling of alcoholic beverages; local interpretations and licensing apply (alcoholic beverage categories are tightly regulated). | Kombucha for retail should meet non-alcoholic labelling requirements and generally target low ABV (often ≤0.5%–1% depending on enforcement). | [86] |
Kombucha’s nutritional profile is characterized by its low caloric density, typically 30–50 kcal per 240 mL (8-ounce) serving, as microbial metabolism progressively reduces the sugar content of the sweetened tea base during fermentation [15, 55]. Carbohydrates, primarily residual sugars, consequently range from 5 to 10 g per serving and decline with extended fermentation.
The beverage's defining components are organic acids produced by its microbial consortium. Acetic acid imparts a characteristic sourness and exhibits antimicrobial properties [11]. Glucuronic acid is implicated in detoxification pathways [11], while lactic acid—produced by lactic acid bacteria (LAB)—may confer probiotic benefits for gut health [9, 58]. Gluconic acid is also thought to support immune function [9, 58].
Kombucha contains trace vitamins, including B1, B2, B6, B12, B3, and vitamin C, though their concentrations depend on fermentation parameters and tea variety [87]. Mineral content, though modest, includes potassium, magnesium, calcium, and iron [88]. As a fermented product, kombucha contains low levels of alcohol, generally between 0.5% and 2.0% ABV, regulated by bacterial oxidation of ethanol to acetic acid [89]. It also harbors probiotics, primarily LAB genera such as Lactobacillus, Leuconostoc, and Bifidobacterium, which may enhance gut microbiota; however, their viability depends on fermentation duration, storage, and processing (e.g., pasteurization) [9, 58].
During fermentation, yeasts hydrolyze sucrose into glucose and fructose for ethanol production, while bacteria metabolize glucose into various organic acids [90]. This microbial activity generates bioactive compounds, notably phenolic substances with potent antioxidant properties (Table 6) [91]. These phenolics mitigate oxidative stress by neutralizing free radicals and are further associated with inhibited carcinogenesis and reduced cholesterol accumulation [92]. Phenolic and flavonoid levels decrease over time due to microbial degradation or polymerization reactions. Table 6 demonstrates that fermentation can either reduce or enhance phenolic constituents depending on substrate characteristics and microbial metabolism.
| Sample | Phenolic | Flavonoid | Inhibition | IC50 | References |
|---|---|---|---|---|---|
| Prickly pear kombucha day 0 |
167.13 ± 11.34 mg GAE /L |
63.65 ± 2.72 mg QE/L |
29.43 ± 1.45% | - | [29] |
| Prickly pear kombucha day 7 |
199.90 ± 30.77 mg GAE /L |
91.44 ± 5.03 mg QE/L |
39.14 ± 7.13% | - | |
| Prickly pear kombucha day 14 |
275.41 ± 29.03 mg GAE /L |
176.44 ± 5.61 mg QE/L |
78.70 ± 2.66% | - | |
| Prickly pear kombucha day 21 |
257.46 ± 16.62 mg GAE /L |
114.15 ± 14.67 mg QE/L |
68.81 ± 8.80% | - | |
|
Ganoderma lucidum kombucha day 8 |
100.41 ± 0.82 mg GAE /L |
17.94 ± 1.22 mg QE/L |
- | 76.97 ±4.01 μL/mL | [30] |
|
Ganoderma lucidum kombucha day 14 |
98.41 ± 0.68 mg GAE /L |
18.56 ± 1.83 mg QE/L |
- | 76.22 ±4.45 μL/mL | |
|
Ganoderma lucidum kombucha day 17 |
96.45 ± 0.74 mg GAE /L |
16.76 ± 1.63 mg QE/L |
- | 75.68 ±3.07 μL/mL | |
| Camellia sinensis kombucha day 8 |
457.58 ± 2.85 mg GAE /L |
83.78 ± 3.27 mg QE/L |
- | 20.79 ±0.85 μL/mL | |
| Camellia sinensis kombucha day 14 |
445.42 ± 0.68 mg GAE /L |
87.69 ± 2.49 mg QE/L |
- | 21.38 ±1.13 μL/mL | |
| Camellia sinensis kombucha day 17 |
479.73 ± 1.32 mg GAE /L |
95.77 ± 1.25 mg QE/L |
- | 21.50 ±0.91 μL/mL | |
| Sea buckthorn kombucha fermentation temperature 20 ℃ |
7.22 ± 0.60 mg GAE /mL |
8.61 ± 0.29 mg RUT /mL |
60.67± 0.88% | - | [31] |
| Sea buckthorn kombucha fermentation temperature 28 ℃ |
10.92 ± 1.10 mg GAE /mL |
9.62 ± 0.36 mg RUT /mL |
86.23± 4.10% | - | |
| Sea buckthorn kombucha fermentation temperature 37 ℃ |
5.01 ± 0.75 mg GAE /mL |
6.91 ± 0.50 mg RUT /mL |
44.09± 1.49% | - | |
| Kombucha without sea buckthorn (GKT) |
22.86 ± 0.66 mg GAE /mL |
9.36 ± 0.35 mg RUT /mL |
21.08± 1.19% | - | |
| Black tea kombucha day 20 |
0.23 ± 0.01 g GAE /L |
4.83 ± 0.01 mg QE/L |
46.67± 0.10% | - | [32] |
| dried pineapple peels and cores sweetened kombucha day 20 |
0.70 ± 0.01 g GAE /L |
10.22 ± 0.01 mg QE/L |
57.83± 0.30% | - | |
| dried pineapple peels and cores, unsweetened kombucha, day 20 |
0.32 ± 0.02 g GAE /L |
6.13 ± 0.02 mg QE/L |
48.07± 0.45% | - | |
| Casacara No Fermentation | 110.8693±0.8471 mg GAE/mL |
1.7717±0.0414 mg QE/mL |
- | 172.36 μg/mL | [33] |
| Casacara 3rd Fermentation day (kombucha) | 113.3867±0.6769 mg GAE/mL |
1.8316±0.0916 mg QE/mL |
- | 146.59 μg/mL | |
| Casacara 7th Fermentation day (kombucha) | 116.1411±0.5419 mg GAE/mL |
2.0743±0.0454 mg QE/mL |
- | 134.17 μg/mL | |
| Casacara 14th Fermentation day (kombucha) | 100.7467±0.2663 mg GAE/mL |
0.6935±0.0055 mg QE/mL |
- | 140.23 μg/mL | |
| Casacara 21st Fermentation day (kombucha) | 112.5219±0.1724 mg GAE/mL |
1.8995±0.0076 mg QE/mL |
- | 159.25 μg/mL | |
| GreenTea Kombucha |
320.1 ± 3.5 mg GAE/L |
181.3 ± 4.8 mg QE/L |
88.23 ± 0.83% | - | [34] |
| BlackTea Kombucha |
206.0 ± 1.2 mg GAE/L |
126.7 ± 5.2 mg QE/L |
61.04 ± 1.99% | - | |
| WhiteTea Kombucha |
228.1 ± 0.5 mg GAE/L |
111.6 ± 2.2 mg QE/L |
70.42 ± 1.38% | - | |
| RedTea Kombucha |
271.9 ± 3.6 mg GAE/L |
242.5 ± 4.8 mg QE/L |
74.78 ± 2.11% | - | |
| Oolong tea kombucha |
555.00±1.00 μg GAE/mL |
863.89±1.47 μg QE/mL |
97.44±0.19% | 17.46±0.07 µL/mL | [35] |
| Royal lotus pollen kombucha |
403.00±2.00 μg GAE/mL |
481.35±5.32 μg QE/mL |
95.20±0.14% | 18.33±1.52 µL/mL | |
| Butterfly pea flower kombucha |
269.08±3.33 μg GAE/mL |
227.65±3.36 μg QE/mL |
98.41±0.19% | 15.65±0.70 µL/mL | |
| cocoa honey kombucha 0 day |
8.37 ± 0.49 mg GAE/mL |
1.15 ± 0.04 mg QE/mL |
53.37 ± 1.54% | - | [36] |
| cocoa honey kombucha 2 days |
58.18 ± 2.03 mg GAE/mL |
1.55 ± 0.03 mg QE/mL |
59.73 ± 1.02% | - | |
| cocoa honey kombucha 4 days |
88.75 ± 0.87 mg GAE/mL |
1.59 ± 0.05 mg QE/mL |
64.29 ± 0.89% | - | |
| cocoa honey kombucha 6 days |
144.75 ± 2.03 mg GAE/mL |
1.78 ± 0.06 mg QE/mL |
70.14 ± 1.15% | - | |
| cocoa honey kombucha 8 days |
117.80 ± 1.14 mg GAE/mL |
1.70 ± 0.05 mg QE/mL |
66.23 ± 0.69% | 180.92 ± 11.63 μg/mL | |
| black tea: roselle (10:0) |
550.63±4.73 µg GAE/mL |
1,000.59±2.02 µg QE/mL |
- | 21.98±0.60 μL/mL | [37] |
| black tea: roselle (8:2) |
525.63±6.14 µg GAE/mL |
779.72±5.46 µg QE/mL |
- | 23.88±0.55 μL/mL | |
| black tea: roselle (7:3) |
486.21±5.94 µg GAE/mL |
630.93±1.16 µg QE/mL |
- | 25.36±0.48 μL/mL | |
| black tea: roselle (6:4) |
480.85±5.28 µg GAE/mL |
595.00±4.81 µg QE/mL |
- | 27.34±0.96 μL/mL | |
| black tea:roselle (5:5) |
413.12±4.07 µg GAE/mL |
443.33±3.33 µg QE/mL |
- | 27.52±1.08 μL/mL | |
| black tea: roselle (0:10) |
220.53±6.50 µg GAE/mL |
148.89±3.33 µg QE/mL |
- | 47.6±2.11 μL/mL | |
| oolong tea kombucha: kitchen mint kombucha: Liquid starter: Cellulose starter (12:0:100:30) |
480.60 ± 5.02 μg GAE/mL |
956.80 ± 31.54 μg QE/mL |
96.00 ± 0.07% | 16.48 ± 0.36 μl/mL | [38] |
| oolong tea kombucha: kitchen mint kombucha: Liquid starter: Cellulose starter (0:12:100:30) |
463.33 ± 3.70 μg GAE/mL |
1874.30 ± 19.09 μg QE/mL |
95.10 ± 0.17% | 39.54 ± 0.81 μl/mL | |
| oolong tea kombucha: kitchen mint kombucha: Liquid starter: Cellulose starter (3:9:100:30) |
459.52 ± 3.41 μg GAE/mL |
1,579.97 ± 33.32 μg QE/mL |
95.48 ± 0.20% | 22.07 ± 0.15 μl/mL | |
| oolong tea kombucha: kitchen mint kombucha: Liquid starter: Cellulose starter (9:3:100:30) |
467.02 ± 0.84 μg GAE/mL |
1,050.00 ± 35.71 μg QE/mL |
95.56 ± 0.29% | 18.59 ± 0.20 μL/mL | |
| oolong tea kombucha: kitchen mint kombucha: Liquid starter: Cellulose starter (2:10:100:30) |
455.36 ± 10.84 μg GAE/mL |
1,593.20 ± 12.48 μg QE/mL |
95.18 ± 0.33% | 35.39 ± 0.22 μL/mL | |
| oolong tea kombucha: kitchen mint kombucha: Liquid starter: Cellulose starter (10:2:100:30) |
468.99 ± 3.04 μg GAE/mL |
1,115.60 ± 31.75 μg QE/ml | 95.24 ± 0.14% | 22.31 ± 0.20 μL/mL | |
| oolong tea kombucha: kitchen mint kombucha: Liquid starter: Cellulose starter (6:6:100:30) |
466.43 ± 3.13 μg GAE/mL |
1,051.60 ± 13.86 μg QE/mL |
95.24 ± 0.16% | 29.26 ± 0.32 μL/mL |
Kombucha is associated with various health benefits, including improved digestion, immune modulation, and detoxification [93]. Its potent antioxidant activity, primarily derived from tea-sourced polyphenols such as catechins, theaflavins, and thearubigins, is a key mechanism. During fermentation, these compounds are biotransformed into bioactive derivatives with enhanced efficacy. They function by donating electrons to free radicals, thereby stabilizing reactive oxygen species (ROS) and preventing oxidative damage to lipids, proteins, and DNA [94]. This activity reduces oxidative stress and platelet aggregation, mitigating the risk of cellular damage [95, 96]. Consequently, regular kombucha consumption may bolster the body's antioxidant capacity, offer cellular protection, and potentially lower the risk of chronic diseases, including cancer and cardiovascular disorders [11].
In addition, kombucha is marketed as a functional beverage due to its fermentation-derived bioactive compounds, including organic acids, polyphenol derivatives, and live microorganisms [93]. However, evidence supporting its health benefits remains predominantly preclinical, with a scarcity of robust human clinical data [56]. For instance, while in vitro studies suggest fermentation can enhance the antioxidant activity of tea polyphenols [94], human evidence for this effect is limited and inconsistent. Consequently, although antioxidant mechanisms may theoretically mitigate oxidative stress, any direct role in reducing the risk of chronic diseases like cancer or cardiovascular disorders remains speculative [94, 97].
A well-documented benefit of kombucha is its promotion of gut health [9, 58]. Its fermentation-derived probiotics aid digestion, enhance nutrient absorption, and fortify the intestinal barrier. Furthermore, organic acids, including acetic, lactic, and gluconic acids, help maintain a gastrointestinal pH that inhibits the growth of pathogenic organisms [57]. These properties collectively support digestive wellness.
Kombucha also exhibits broad-spectrum antimicrobial activity, largely attributed to its acetic acid content, which inhibits pathogens such as Escherichia coli, Salmonella, and Staphylococcus aureus [50, 72]. This functionality positions it not only as a health tonic but also as a potential agent for food preservation and treating minor infections [97].
Organic acids, including acetic, gluconic, and glucuronic acids, are principal metabolites in kombucha, produced through the sequential oxidation of ethanol by acetic acid bacteria [50]. While glucuronic acid is often attributed with detoxifying properties and acetic acid demonstrates antimicrobial activity in vitro, the physiological relevance of these functions in humans remains unsubstantiated [94].
Proposed gut health benefits, primarily linked to the activity of lactic acid bacteria, are similarly constrained. Current evidence derives largely from preclinical models, with insufficient clinical data to confirm reliable digestive benefits in humans [88, 90]. Consequently, the microbial content of kombucha is more accurately described as "live microorganisms" rather than validated probiotics, as the latter requires demonstrated health benefit in controlled human trials.
The beverage's biochemical profile is defined by this microbial synergy: yeasts initiate fermentation by hydrolyzing sucrose to produce ethanol, which acetic acid bacteria then oxidize to organic acids. The contingent presence of lactic acid bacteria can further modulate acidity and flavor. This consortium-driven metabolism ultimately defines the chemical composition and purported, though often not clinically verified, bioactivity of the final product [94, 97].
Clinical trials demonstrate kombucha's modulatory effects on the human gut microbiome. In a pre-post intervention, Costa et al. [98] provided black tea kombucha to 46 participants, including normal-weight and obese individuals. After 8 weeks, both groups exhibited altered gut microbiota, with a significant reduction in diabetes-associated genera such as Ruminococcus and Dorea; this effect was more pronounced in obese subjects.
In a separate randomized trial, Arce-López et al. [99] administered either 250 mL of unfermented tea (control) or a fiber-enriched kombucha to 60 volunteers for 6 weeks. The kombucha group showed significant improvements in gut microbiota composition and biochemistry, including a considerable reduction in triglyceride levels. The treatment also reduced pro-inflammatory Ruminococcus and increased the abundance of beneficial, immunomodulatory Bifidobacterium.
Emerging evidence suggests that kombucha may help prevent and manage chronic disease. Its antioxidant and anti-inflammatory properties have the potential to mitigate the risk of metabolic disorders, such as type 2 diabetes. Preclinical studies indicate it can regulate blood glucose, improve lipid profiles, and support hepatic detoxification pathways [100].
However, consumption requires moderation. The beverage’s high acidity may cause adverse effects, including acidosis, while non-sterile production risks microbial contamination. Therefore, commercially produced kombucha, manufactured under stringent quality controls, is generally recommended. Thus, kombucha represents a functional beverage whose documented antioxidant, antimicrobial, and probiotic properties, alongside its emerging therapeutic potential, are supported by a growing body of research [11].
Ultimately, safety considerations are crucial when evaluating kombucha’s functional properties. Although generally considered safe when properly prepared, risks such as acidosis and contamination have been reported, particularly in home-brewed products. Vulnerable populations, including pregnant women, immunocompromised individuals, and patients with liver disease, may be at greater risk from uncontrolled fermentation, variable alcohol content, or excessive acidity. Ensuring hygienic production and monitoring product composition are therefore critical to safeguarding consumer health [94, 97].
Despite its overall safety, kombucha poses food safety risks that require careful management. Inadequate sanitation can introduce pathogenic bacteria like Escherichia coli, Salmonella spp., and Listeria monocytogenes [52]. Over-fermentation can produce excessive acidity, potentially irritating the gastric mucosa, and may elevate alcohol beyond the legal limit for non-alcoholic beverages [21]. Conversely, insufficient acidification can permit mold growth (e.g., Aspergillus spp.), risking mycotoxin contamination [56]. Certain individuals, particularly those with yeast sensitivities or immunocompromised states, may also experience adverse reactions [101].
Mitigating these hazards necessitates stringent protocols: rigorous equipment sanitation, high-quality ingredients, and controlled fermentation between 20–26 °C. Maintaining a pH below 4.2 is critical to inhibit pathogen proliferation [52]. Products should be stored in sterile, sealed containers under refrigeration to prevent further microbial growth [102].
Consumer education is also vital. It is important to inform consumers of the potential risks associated with homemade kombucha and provide clear labelling on commercial products, including alcohol content and allergen information. Food safety is a central consideration in the production and consumption of kombucha [3]. Potential risks include microbial contamination, over-fermentation, and variability in acidity and alcohol content, particularly in home-brewed preparations. Excessive acidity may contribute to metabolic acidosis in sensitive individuals, while uncontrolled fermentation can lead to elevated ethanol levels that exceed permissible limits. Contamination with molds or mycotoxins has also been reported when hygienic practices are not followed. These issues highlight the importance of controlled production, proper storage, and adherence to safety standards [98]. In the United States, regulatory oversight of kombucha is divided between agencies. The Food and Drug Administration (FDA) regulates kombucha as a food product with respect to safety, labelling, and good manufacturing practices. At the same time, the Alcohol and Tobacco Tax and Trade Bureau (TTB) assume regulatory authority if the alcohol content exceeds 0.5% alcohol by volume, classifying the beverage as alcoholic. This division underscores the importance of monitoring alcohol levels both during and after fermentation [98, 99].
Globally, regulatory frameworks for kombucha vary by region. In the European Union, kombucha may fall under the Novel Food Regulation if certain production methods or ingredients are used, requiring pre-market authorization. Other jurisdictions, such as Australia, Canada, and several Asian countries, apply different standards regarding permissible alcohol content, labelling, and health claims. While harmonization is limited, these examples illustrate that kombucha safety is not only a scientific matter but also a regulatory one, depending on regional policies and consumer protection frameworks [98, 100]. Adherence to these standards ensures the product's safety and legality. When produced under controlled conditions and following proper food safety protocols, kombucha can be a safe and enjoyable beverage. By maintaining stringent hygiene practices, monitoring fermentation, and complying with regulatory guidelines, producers can minimize risks and allow consumers to enjoy the health benefits and distinctive flavors of kombucha without compromising safety [101].
Commercial kombucha production faces significant challenges in ensuring product consistency, safety, and regulatory compliance. Microbiologically, maintaining a stable SCOBY composition is critical, as variations lead to inconsistencies in flavor, acidity, and carbonation. The traditional open fermentation also increases the risk of mold or wild-yeast contamination, necessitating stringent hygiene protocols [22]. Chemically, the dual task of managing residual sugar for taste and fermenting it to keep alcohol below the 0.5% ABV threshold for non-alcoholic beverages requires precise control [3].
Scaling production introduces further hurdles, including maintaining consistent flavor and stable carbonation across industrial batches while avoiding over-carbonation and packaging failure [103, 104]. Regulatory landscapes remain complex and fragmented, with stringent requirements for alcohol content, labelling, and health claims, compounded by a lack of global standardization [67, 105]. Consequently, balancing cost-effective production with high-quality raw materials and rigorous testing remains a central challenge for the industry [106].
The future development of kombucha faces several significant challenges, including microbial variability, contamination risks, over-fermentation, chemical and mechanistic uncertainties, industrial-scale reproducibility, and regional regulatory differences [21]. At the same time, there are multiple opportunities to enhance its value as a functional beverage. Potential directions include fortification with bioactive compounds, flavor diversification to improve consumer acceptance, and the valorization of cellulose by-products for sustainable applications [22]. Future research should also focus on enhancing live microorganisms with potential probiotic properties in kombucha to increase its functional relevance, while acknowledging that most SCOBY-associated microbes have not yet been clinically validated as probiotics [3]. Advances in digital technologies, such as artificial intelligence (AI) and the Internet of Things (IoT), may further enhance the monitoring and control of fermentation processes, thereby supporting product standardization and safety [100]. In addition, integrating fermentation data with consumer health records could, in the long term, enable the design of personalized functional beverages [101]. Currently, however, this concept remains highly speculative and should be viewed as a potential future direction rather than an imminent application [102]. Taken together, these developments highlight both the challenges and the exciting opportunities for kombucha innovation in the years ahead [103].
Despite production and regulatory challenges, the global kombucha market is projected to grow substantially, driven by consumer demand for functional beverages [56, 107]. Its appeal is rooted in perceived health benefits from its probiotic and antioxidant content, though robust clinical evidence for many claims remains limited [57, 108]. Future success hinges on navigating increased regulatory scrutiny and intense competition from other functional drinks [109].
Significant opportunities lie in product innovation, such as nutrient fortification and novel flavors, as well as in expansion into emerging markets [61]. Advancements in fermentation technology and a commitment to sustainable practices, including eco-conscious packaging, will be critical for ensuring consistent quality and aligning with consumer values [25]. Ultimately, kombucha’s trajectory is tied to global health trends, and its sustained growth will depend on reconciling its artisanal nature with the demands of industrial-scale production and scientific validation [110, 111].
Kombucha's rapid market expansion is fueled by its unique sensory appeal and perceived health benefits. However, its production faces significant challenges in microbial control, alcohol management, and regulatory compliance, necessitating precise fermentation management to ensure safety and consistency. While in vitro and animal studies suggest bioactivity, robust clinical evidence of human health benefits remains limited. Future growth and market legitimacy depend on two critical pillars: advancing production technology to overcome scalability and safety hurdles, and substantiating consumer health claims through rigorous, controlled human trials. Only by bridging this gap between traditional appeal and scientific validation can kombucha secure its long-term position as a credible functional beverage.
Lutfi Anshory: Conceptualization, Methodology, Investigation, Writing- Original draft preparation, Writing- Reviewing and Editing. R. Haryo Bimo Setiarto: Conceptualization, Methodology, Investigation, Supervision, Writing- Original draft preparation, Writing- Reviewing and Editing. Dimas Andrianto: Data curation, Supervision, Writing- Reviewing and Editing. Andri Frediansyah: Writing- Original draft preparation
