Microbial interactions and dynamic changes of volatile flavor compounds during the fermentation of traditional kombucha

Analysis of changes in volatile metabolites of pickled radish in different years using GC-MS, OAV and multivariate statistics

Pickled radish is a local specialty fermented food, loved for its unique flavor. In this study, the volatile components of pickled radish from different years were identified and analyzed, and 82 volatile metabolites were finally identified and 39 volatile differential metabolites were screened out, which showed that the contents of γ-butyrolactone, 3-furaldehyde and ethyl lactate showed an increasing trend. Odor activity value (OAV) analysis showed that 3-furaldehyde, dimethyl tetrasulphide and linolenic acid were important aroma components in pickled radish. In addition, the potential pathways for the formation of volatile metabolites in pickled radish were preliminarily constructed based on the KEGG database, in which alcohols, aldehydes and acids contributed to the formation of the unique flavor of pickled radish. The present study reveals the systematic changes of volatile metabolites in pickled radish and provides a new perspective to understand the changes of its flavor characteristics.

Kombucha: An Old Tradition into a New Concept of a Beneficial, Health-Promoting Beverage

Kombucha is an ancient, fermented beverage that has gained increasing popularity worldwide due to its potential health benefits. Its origins trace back to China, from where it spread across Asia and Europe before reaching the modern global market. The fermentation of kombucha is mediated by a Symbiotic Culture of Bacteria and Yeasts (SCOBY), comprising yeasts, acetic acid bacteria, and lactic acid bacteria. The microbial consortium plays a crucial role in the production of organic acids and bioactive metabolites, shaping the sensory characteristics of the beverage. Given the growing interest in kombucha as a functional beverage, this study aims to explore its historical background, fermentation process, and microbiological composition, including key yeasts, acid acetic bacteria, and lactic acid bacteria and their interactions. Additionally, we describe the potential health effects of kombucha, particularly its antimicrobial and antioxidant activity, the probiotic potential of the strains associated with kombucha, and safety considerations while also addressing the risks associated with its consumption. Although several studies suggested that kombucha may have antioxidants, antimicrobial, and probiotic properties, as well as contribute to gut microbiota regulation and immune system support, there is significant variability in the composition of the beverage, especially in artisanal preparations. This variability poses challenges in standardizing its potential effects and ensuring consistent safety. The risk of contamination further underscores the importance of adhering to strict sanitary production standards. To scientifically validate its health benefits and guarantee safe consumption, further research with larger sample sizes and robust methodologies is essential. The findings of this study will contribute to a deeper understanding of the functional properties of kombucha and provide scientific support for its safe and beneficial applications.

Exploiting agri-food residues for kombucha tea and bacterial cellulose production

Bio-valorization of agri-food wastes lies in their possible conversion into fermented foodstuffs/beverages and/or biodegradable polymers such as bacterial cellulose. In this study, three different kombucha cultures were formulated using agri-food waste materials, citrus fruit residues and used coffee grounds, as alternative carbon and nitrogen sources, respectively. Over 21 days of fermentation, the kinetic profile was followed by monitoring cell density, pH variation, minerals, trace elements and production of bacterial cellulose. Moreover, the total phenolic and radical scavenging capacity was measured by spectrophotometric tests on the beverage and bacterial cellulose. Several classes of compounds were detected by gas chromatography coupled with mass spectrometry performing extractions on the headspace above fresh kombucha beverages and their lyophilized fractions, using solid phase micro extraction and liquid phase extraction, respectively. The obtained results allowed assessing molecular profiles of each kombucha beverages. A chemometric meta-analysis of the data revealed the individual impacts of the single ingredients and the effects of the fermentation process.

Thai Cannabis sativa Leaves as a Functional Ingredient for Quality Improvement and Lactic Acid Bacterial Growth Enhancement in Kombucha

Kombucha is a well-known fermented drink that gained interest due to its gut health benefits. However, it has a harsh taste of acetic acid and is hard to consume. Thai Cannabis leaves (Cannabis sativa sp. Hang Kra Rog Phu phan ST1) contain high protein and phytochemicals which can improve the growth of lactic acid bacteria (LAB) and enhance the organoleptic quality of the Kombucha. This study revealed the effect of infusing assam green tea leaves with cannabis leaves on the fermentation rate, microbial communities, volatile compounds, and overall quality and taste of the kombucha. The high protein content (23.10%) of Cannabis leaves was found. Phytonutrients and phytochemicals found in the leaves promotes LAB growth, which resulted in the higher number of LAB in the treatment with cannabis leaves. At the end of fermentation (day 7), the highest LAB count (5.53 log CFU mL-1) was presented in kombucha infused with 30% cannabis leaves. Kombucha with better quality, higher pH, and less acidity was obtained in a dose manner. The change in microbial communities was detected using metagenomic analysis. The prominence of Dekkera and Komagataeibacter, with low abundance of Zygosaccharomyces and Weissella were identified. These microorganisms improved flavor by lessening strong fermented odor and harsh acidic taste. From volatile compounds, HS-SPME-GCMS revealed that kombucha infused with 30% cannabis leaves possessed less acetic acid, ethanol, and carbon dioxide and gave a better odor and taste. Hence, cannabis leaves was the novel substrate for kombucha fermentation by enhancing LAB growth and improving the overall qualities.

Effects of Lemongrass Essential Oil on Key Aromas of Pickled Radish During Storage Using HS-GC-IMS and in Silico Approaches

To investigate the effects of lemongrass essential oil on the key volatile aroma compounds of pickled radish (PR) during storage, this study used headspace-gas chromatography-ion mobility spectrometry, fingerprint analysis, multivariate statistical analysis, and molecular docking to study different PR samples. The results indicated that a total of 48 volatile aromatic compounds were identified. Fingerprint analysis revealed that the aroma profiles of samples at different storage stages were different. Using the screening criteria of p < 0.05 and variable importance for the projection > 1 in multivariate statistical analysis, and relative odor activity value > 1, six potential key aroma compounds were selected. Furthermore, phenylethyl acetate, β-ocimene, 4-heptanone, and limonene were determined as the key aroma compounds that affect the PR aroma profile after adding lemongrass essential oil. Moreover, the addition of lemongrass essential oil increased the fruit and sweet aroma of PR samples during storage. The results of molecular docking indicated that the recognition of these four odors was mainly accomplished through hydrophobic interactions and hydrogen bond interactions by docking OR1A1 and OR5M3 receptors. This study can offer a preliminary foundation and theoretical support for the in-depth exploration of the paocai industry.

Utilizing kombucha culture for coffee fermentation and biochemical characteristic analysis

Coffee, an important global commodity, is grown on 10.2 million hectares in over 80 countries. Arabica coffee (Coffea arabica) is popular worldwide due to its superior flavour. As consumer interest in coffee flavour and quality continues to grow, this study aims to enhance the bioactive compounds, functionality, and sensory properties of Arabica coffee (Coffea arabica) by fermentation with black tea kombucha (K-coffee) and coffee kombucha (CK-coffee). Coffee showed a decrease in pH and an increase in titratable acidity during fermentation. The total phenolic and flavonoid content increased 1.77- and 1.95-fold in K-coffee and 2.07- and 2.60-fold in CK-coffee, respectively, after 24 h of fermentation compared to the coffee control, in which the kombucha broth was not inoculated, with an increased in trigonelline, chlorogenic acid and caffeic acid content. The caffeine content in CK-coffee increased 1.33-fold after 12 h of fermentation and remained relatively stable in K-coffee up to 24 h of fermentation compared to the coffee control. The antioxidant activity and inhibitory effect against α-glucosidase of fermented coffee increased to 2.24- and 2.40-fold after 24 h of fermentation, respectively, compared to the coffee control. Sensory evaluation highlighted noticeable differences in flavour among unfermented coffee, K-coffee, and CK-coffee with changes in volatile aroma compounds. These results support the feasibility of kombucha fermentation as a novel approach to develop specialty coffees with enhanced flavour and nutritional profiles.

Dynamic changes in microbial communities and volatile compounds in kombucha fermentation using Flos sophorae and Elm fruits, compared to black and green tea

The dynamic changes in physicochemical properties, microbial communities, and volatile compounds in kombucha made from Flos sophorae (FLSK) and Elm fruit (EFK) were compared to those of black tea (BTK) and green tea (GTK) over a 12-day fermentation period. The results revealed that overall flavonoid and polyphenol content, as well as antioxidant activity, increased initially and then decreased, accompanied by a steady reduction in pH within the fermentation broths investigated. Notably, the GTK exhibited stronger antioxidant activity than the other fermentation broths. Furthermore, 16S rRNA gene sequencing revealed that Komagataeibacter rhaeticus, Komagataeibacter saccharivorans, and Acidovorax wautersii were the dominating microbial species in the fermentation broths under this study. Komagataeibacter rhaeticus initially reduced and then increased throughout the FLSK fermentation, whereas Komagataeibacter saccharivorans increased from day 0 to day 6, and remain stable by day 12 during the EFK fermentation. Comparative analysis revealed that Komagataeibacter rhaeticus was more abundant in the FLSK and GTK than in the EFK and BTK, whereas Komagataeibacter saccharivorans showed a higher abundance in the EFK relative to the other fermentation broths. Gas chromatography-mass spectrometry identified acetic acid, linalool, ethanol, and ethyl acetate as the major volatile chemicals that rose significantly in fermentation mixtures of the examined substrates. The FLSK had a much higher linalool concentration than the other fermentation broths, although the EFK and GTK had higher ethanol content. Correlation study found that Komagataeibacter rhaeticus was negatively related with alcohol compounds, but Komagataeibacter saccharivorans was positively associated with a diverse spectrum of acids, alcohols, and esters. The study found changes in bioactive chemicals as well as interactions between bacterial populations and volatile compounds throughout fermentation in the substrates investigated.

Exploring the dynamic characteristic of typical kombucha induced by symbiotic microbiota succession from four Chinese regions: A comprehensive analytical framework

To investigate the microbial diversities and dynamic quality properties of kombucha, the successional changes with different periods from four regions were comprehensively characterized and compared. A total of 197 indigenous yeast and bacterial strains were isolated, involving Gluconobacter, Komagataeibacter, Starmerella and Zygosaccharomyces spp. The successional dynamics of the kombucha communities in different regions were evaluated. The b* values of all kombucha decreased continuously as fermentation progressed. Results indicated that proper fermentation timing significantly influenced nutritional composition and aroma characteristics. A gradual increase in the content of individual monomeric phenols during the middle and late stages of fermentation (days 6-15). Overall, the Shaanxi (SX) region exhibited the highest content of the 10 phenolics detected on day 9, with 273.45 mg/L, followed by the Hunan (HN) region on day 9 (206.49 mg/L). Higher concentrations of bioactive compounds were produced during later stages, which determined the antioxidant properties. A total of 94 volatile compounds were identified and 32 volatiles with relative odor activity value (rOAV) ≥ 0.1. Four regions showed a decreasing trend in the number of aromas in the later stages of fermentation. The predominant compounds were acids, esters and alcohols during the later fermentation stages, which decanal, trans-β-ionone and damascenone serving as characteristic aromas. The partial least-squares regression analysis revealed that apple juice, fruity and sour apple odors showed an intensely positive impact on the overall acceptability of the kombucha.

Chemical, microbial, and functional characterization of a new fruity probiotic kombucha

This study aimed to evaluate the effect of adding Lacticaseibacillus casei as probiotic culture and/or camu-camu (Myrciaria dubia) pulp on the chemical profile, technological, functional, and sensory properties, phenolics concentration and bioaccessibility, and microbiota of kombucha. Adding L. casei decreased some volatile compounds and fruity flavor intensity and increased the Lactobacillus relative abundance (+35.73 %) and lactic acid content (from 1.26 to 1.54 g/L), decreasing flavor and overall impression acceptances. Adding camu-camu pulp resulted in more acidic products (pH of 2.75 vs 3.24), with a higher concentration of some phenolic compounds. The kombucha with L. casei and camu-camu pulp was characterized by a higher concentration of citric and acetic acids, ethanol, ascorbic acid, and most of the phenolic compounds and volatile compounds, higher bioaccessibility of phenolic compounds, increased consistency index, improved functional properties (inhibition of α-glucosidase and antioxidant activity), and better sensory properties. Furthermore, it showed an increased relative abundance of Lactobacillus (+15.11 %) and a decreased relative abundance of Acetobacter (-5.56 %) and Komagataeibacter (-9.12 %) compared to the conventional kombucha. L. casei survived the processing (> 7 log CFU/mL) and simulated gastrointestinal conditions (>5 log CFU/mL). In conclusion, the association of L. casei and camu-camu pulp resulted in potentially probiotic kombuchas with improved chemical profile, functional, technological, and sensory properties, phenolic compounds concentration and bioaccessibility, and bacterial microbial diversity.

Study on the Interaction between Polyol Glycerol and Flavor Compounds of Baijiu: A New Perspective of Influencing Factors of Baijiu Flavor

The interaction among flavor compounds is a crucial determinant of Baijiu's flavor. Yet, the interaction between glycerol, a prominent polyol in Baijiu, and volatile flavor compounds remains elusive. The effect of glycerol concentration on the volatility of 13 Baijiu flavor compounds was analyzed by GC-IMS and GC-MS. The findings reveal that glycerol's impact on the volatility of these compounds increases with its concentration. Postglycerol addition, olfactory threshold and S-curve analyses reveal a decrease in the perception threshold of dimethyl trisulfide, while the perception thresholds of 3-methylbutanal, 1-propanol, 2-methyl-1-propanol, and ethyl lactate increase. Additionally, the independent gradient model based on Hirshfeld partitioning showed that hydrogen bonding is crucial in the interactions, aligning well with GC-IMS and odor threshold results to underscore glycerol's consistent impact on Baijiu flavor compounds. This research highlights glycerol's significant role in shaping Baijiu's complex flavor profile, enhancing our understanding of flavor interactions.

Revealing novel insights into the enhancement of quality in black tea processing through microbial intervention

Black tea is highly favored by consumers worldwide, with enzymatic reactions being recognized as a pivotal factor influencing tea quality. The role of microorganisms in shaping the composition of black tea has emerged as a focus of research due to their involvement in enzyme catalysis and metabolic processes. In this study, full-length amplicon sequencing combined with qPCR more accurately reflected microbial profile, and Pantoea, Pseudomonas, Paucibacter, and Cladosporium were identified as the main microbial genera. Moreover, by comprehensively analyzing color, aroma, and taste components over time in black tea samples, correlations were established between the dominant genus and various quality factors. Notably, peroxidase activity levels, total soluble sugar content, and tea pigments concentration exhibited significant associations with the dominant genus. Consequently, this microbiological perspective facilitated the exploration of driving factors for improving black tea quality while establishing a theoretical foundation for quality control in industrial production.

Kombucha with yam: Comprehensive biochemical, microbiological, and sensory characteristics

Consumer demand for functional foods has increased, helping to popularize and increase the consumption of Kombucha. Other substrates have been used together with tea to improve the functional and sensory properties of the beverage. Thus, this study evaluated the comprehensive biochemical, microbiological, and sensory characteristics of kombuchas fermented with green tea (Camellia sinensis) and different concentrations of yam (0, 10, and 20 % w/v). Based on pre-tests to detect the best concentration of yam in the beverage (10, 20, 30, and 40 %) and fermentation time (5, 7, and 14 days),the concentrations of 10 and 20 % of yam and five days of fermentation were selected through pH, °Brix, and sensory analysis. During the kombucha fermentation, there was a decrease in °Brix and pH. Sucrose, glucose, fructose, citric, and succinic acids were related to the beginning of fermentation, and lactic and acetic acids were more related to the end of fermentation in the treatment containing 20 % yam. The fermentation time did not change the color of the kombucha. Fatty acids, phenols, terpenoids, and alcohols were the volatile groups with the most compounds identified. Only two yeast genera were identified (Brettanomyces bruxellensis and Pichia membranifaciens), and bacteria of the genera Acetobacter, Lactobacillus, Pantoea, Pseudomonas, Azospirillum, and Enterobacter. The beverage control showed less turbidity and more clear. The fruity descriptor was more perceived in treatments with yam. However, the perception of the apple descriptor decreases as the yam concentration increases. The yam's concentration alters the kombucha's microbiota and sensory characteristics, mainly appearance and acidity. Kombucha fermentation using yam extract is viable, and the product is sensorially accepted. However, technological improvements, such as yam flour, could be made mainly for appearance and taste attributes.

Nature of back slopping kombucha fermentation process: insights from the microbial succession, metabolites composition changes and their correlations

Kombucha, a fermented tea prepared with a symbiotic culture of bacteria and yeast (SCOBY), offers a unique and unpredictable home-brewed fermentation process. Therefore, the need for a controlled kombucha fermentation process has become evident, which requiring a thorough understanding of the microbial composition and its relationship with the metabolites produced. In this study, we investigated the dynamics of microbial communities and metabolites over a 12-day fermentation period of a conventional kombucha-making process. Our findings revealed similarities between the microbial communities in the early (0-2 days) and late (10-12 days) fermentation periods, supporting the principle of back-slopping fermentation. Untargeted metabolite analysis unveiled the presence of harmful biogenic amines in the produced kombucha, with concentrations increasing progressively throughout fermentation, albeit showing relatively lower abundance on days 8 and 12. Additionally, a contrasting trend between ethanol and caffeine content was observed. Canonical correspondence analysis highlighted strong positive correlations between specific bacterial/yeast strains and identified metabolites. In conclusion, our study sheds light on the microbial and metabolite dynamics of kombucha fermentation, emphasizing the importance of microbial control and quality assurance measures in the production process.

Volatilome, Microbial, and Sensory Profiles of Coffee Leaf and Coffee Leaf-Toasted Maté Kombuchas

Kombucha is a fermented beverage traditionally made from the leaves of Camelia sinensis. The market has drastically expanded recently, and the beverage has become more elaborated with new, healthy food materials and flavors. Pruning and harvesting during coffee production may generate tons of coffee leaves that are discarded although they contain substantial amounts of bioactive compounds, including those found in maté tea and coffee seeds. This study characterized the changes in volatilome, microbial, and sensory profiles of pure and blended arabica coffee leaf tea kombuchas between 3-9 days of fermentation. Acceptance was also evaluated by consumers from Rio de Janeiro (n = 103). Kombuchas (K) were prepared using black tea kombucha starter (BTKS) (10%), sucrose (10%), a symbiotic culture of Bacteria and Yeasts (SCOBY) (2.5%), and a pure coffee leaf infusion (CL) or a 50:50 blend with toasted maté infusion (CL-TM) at 2.5%. The RATA test was chosen for sensory profile characterization. One hundred volatile organic compounds were identified when all infusions and kombucha samples were considered. The potential impact compounds identified in CL K and CL-TM K were: methyl salicylate, benzaldehyde, hexanal, nonanal, pentadecanal, phenylethyl-alcohol, cedrol, 3,5-octadien-2-one, β-damascenone, α-ionone, β-ionone, acetic acid, caproic acid, octanoic acid, nonanoic acid, decanoic acid, isovaleric acid, linalool, (S)-dihydroactinidiolide, isoamyl alcohol, ethyl hexanoate, and geranyl acetone. Aroma and flavor descriptors with higher intensities in CL K included fruity, peach, sweet, and herbal, while CL-TM K included additional toasted mate notes. The highest mean acceptance score was given to CL-TM K and CL K on day 3 (6.6 and 6.4, respectively, on a nine-point scale). Arabica coffee leaf can be a co-product with similar fingerprinting to maté and black tea, which can be explored for the elaboration of potentially healthy fermented beverages in food industries.

Unraveling symbiotic microbial communities, metabolomics and volatilomics profiles of kombucha from diverse regions in China

Kombucha is a natural fermented beverage (mixed system). This study aimed to unravel the signatures of kombucha in China to achieve tailor-made microbial consortium. Here, biochemical parameters, microbiome, metabolite production and volatile profile were comprehensively compared and characterized across four regions (AH, HN, SD, SX), both commonalities and distinctions were highlighted. The findings revealed that yeast species yeast Starmerella, Zygosaccharomyces, Dekkera, Pichia and bacterium Komagataeibacter, Gluconobacter were the most common microbes. Additionally, the composition, distribution and stability of microbial composition in liquid phase were superior to those in biofilm. The species diversity, differences, marker and association were analyzed across four areas. Metabolite profiles revealed a total of 163 bioactive compounds (23 flavonoids, 13 phenols), and 68 differential metabolites were screened and identified. Moreover, the metabolic pathways of phenylpropanoids biosynthesis were closely linked with the highest number of metabolites, followed by flavonoid biosynthesis. Sixty-five volatile compounds (23 esters) were identified. Finally, the correlation analysis among the microbial composition and volatile and functional metabolites showed that Komagataeibacter, Gluconolactone, Zygosacchaaromycess, Starmerella and Dekkera seemed closely related to bioactive compounds, especially Komagataeibacter displayed positive correlations with 1-hexadecanol, 5-keto-D-gluconate, L-malic acid, 6-aminohexanoate, Starmerella contributed greatly to gluconolactone, thymidine, anabasine, 2-isopropylmalic acid. Additionally, Candida was related to β-damascenone and α-terpineol, and Arachnomyces and Butyricicoccus showed the consistency of associations with specific esters and alcohols. These findings provided crucial information for creating a stable synthetic microbial community structure, shedding light on fostering stable kombucha and related functional beverages.