Understanding the effect of fermentation time on physicochemical characteristics, sensory attributes, and volatile compounds in green tea kombucha

Kombuchas are a trend in the fermented beverage field and the effect of fermentation time on their characteristics is necessary to better understand the process, mainly concerning volatile compounds, which are scarce information in the current literature. Thus, the present work aimed to evaluate the features of green tea kombucha during fermentation, monitoring the changes in pH, acidity, turbidity, polyphenols, ethanol, acetic acid, volatile compounds, and sensory profile and acceptance up to 14 days of fermentation. Kombuchas' pH and acidity decreased through time as expected, but after 4 days of fermentation, the beverage exceeded the Brazilian legal limits of acidity (130 mEq/L) and produced more than 0.5% AVB, which labels the beverage as alcoholic. Total polyphenols and condensed tannins content enhanced until the seventh day of fermentation and remained constant. Fermentation highly impacted the aroma of the infusion with a high formation of volatile acids, such as alcohols, esters, and ketones. Aldehydes were degraded during the bioprocess. Sensory characterization of kombucha showed that fermentation of 4 days increased perceived turbidity; vinegar, citric fruit, acid, and alcoholic aroma; and produced the beverage with sour, bitter, and vinegar flavor. Thus, the fermentation time of kombuchas must be controlled as they rapidly change and impact on the physicochemical parameters and sensory profile of the beverage can be negative.

Research progress on alternative kombucha substrate transformation and the resulting active components

Kombucha is a customary tea-based beverage that is produced through the process of fermenting a mixture of tea and sugar water with symbiotic culture of bacteria and yeast (SCOBY). Traditional kombucha has various beneficial effects and can improve immunity. The significant market share of Kombucha can be attributed to the growing consumer inclination towards healthy foods within the functional beverage industry. The research focus has recently expanded from the probiotics of traditional black tea kombucha to encompass other teas, Chinese herbs, plant materials, and alternative substrates. There is a lack of comprehensive literature reviews focusing on substance transformation, functional, active substances, and efficacy mechanisms of alternative kombucha substrates. This article aimed to bridge this gap by providing an in-depth review of the biological transformation pathways of kombucha metabolites and alternative substrates. The review offers valuable insights into kombucha research, including substance metabolism and transformation, efficacy, pharmacological mechanism, and the purification of active components, offering direction and focus for further studies in this field.

Antioxidant Activities, Phenolic Compounds, and Sensory Acceptability of Kombucha-Fermented Beverages from Bamboo Leaf and Mulberry Leaf

Kombucha is traditional drink made from the fermentation of a black tea infusion, and is believed to offer a variety of health benefits. Recently, exploring kombucha made from alternative substrates has become a research hotspot. In this paper, two novel kombucha beverages were produced with bamboo leaf or mulberry leaf for the first time. Moreover, the effects of fermentation with leaf residues (infusion plus residues) or without leaf residues (only infusion) on the antioxidant properties of kombucha were compared. The ferric-reducing antioxidant power assay, Trolox equivalent antioxidant capacity assay, Folin-Ciocalteu method, and high-performance liquid chromatography were utilized to measure the antioxidant capacities, total phenolic contents, as well as some compound concentrations of the kombucha. The results showed that two types of kombucha had high antioxidant capacities. Moreover, kombucha fermented with bamboo leaf residues (infusion plus residues) significantly enhanced its antioxidant capabilities (maximum increase 83.6%), total phenolic content (maximum increase 99.2%), concentrations of some compounds (luteolin-6-C-glucoside and isovitexin), and sensory acceptability, compared to that without residues (only infusion). In addition, fermentation with leaf residues had no significant effect on mulberry leaf kombucha. Overall, the bamboo leaf was more suitable for making kombucha with residues, while the mulberry leaf kombucha was suitable for fermentation with or without residues.

Development of Fermented Kombucha Tea Beverage Enriched with Inulin and B Vitamins

Kombucha is a sweet and sour beverage made by fermenting a liquid base with a symbiotic culture of bacteria and yeast. Different tea substrates, carbohydrate sources, and additional ingredients are used to create beverages with different physical and chemical characteristics. The purpose of this work was to create a recipe and technology to study the properties of the beverage based on kombucha with a given chemical composition. The content of added functional ingredients (vitamins and inulin) in quantities comparable with reference daily intake was the specified parameter characterizing the distinctive features of the enriched beverages. For fermentation using symbiotic cultures of bacteria and yeast, a black tea infusion sweetened with sucrose was used as a substrate. The changes in the physicochemical characteristics of the fermented tea beverage base were evaluated. The dynamics of changes in pH, acidity, the content of mono- and disaccharides, ethanol, organic acids, polyphenolic compounds, and volatile organic substances were shown. The fermentation conditions were selected (pH up to 3.3 ± 0.3, at T = 25 ± 1 °C, process duration of 14 days) to obtain the beverage base. Strawberry and lime leaves were used as flavor and aroma ingredients, and vitamins with inulin were used as functional ingredients. Since the use of additional ingredients changed the finished beverage’s organoleptic profile and increased its content of organic acids, the final product’s physical–chemical properties, antioxidant activity, and organoleptic indicators were assessed. The content of B vitamins in the beverages ranges from 29 to 44% of RDI, and 100% of RDI for inulin, which allows it to be attributed to the category of enriched products. The DPPH inhibitory activity of the beverages was 82.0 ± 7%, and the ethanol content did not exceed 0.43%. The beverages contained a variety of organic acids: lactic (43.80 ± 4.82 mg/100 mL), acetic (205.00 ± 16.40 mg/100 mL), tartaric (2.00 ± 0.14 mg/100 mL), citric (65.10 ± 5.86 mg/100 mL), and malic (45.50 ± 6.37 mg/100 mL). The technology was developed using pilot equipment to produce fermented kombucha tea enriched with inulin and B vitamins.

Reconstruction of Simplified Microbial Consortia to Modulate Sensory Quality of Kombucha Tea

Kombucha is a fermented tea with a long history of production and consumption. It has been gaining popularity thanks to its refreshing taste and assumed beneficial properties. The microbial community responsible for tea fermentation—acetic acid bacteria (AAB), yeasts, and lactic acid bacteria (LAB)—is mainly found embedded in an extracellular cellulosic matrix located at the liquid–air interphase. To optimize the production process and investigate the contribution of individual strains, a collection of 26 unique strains was established from an artisanal-scale kombucha production; it included 13 AAB, 12 yeasts, and one LAB. Among these, distinctive strains, namely Novacetimonas hansenii T7SS-4G1, Brettanomyces bruxellensis T7SB-5W6, and Zygosaccharomyces parabailii T7SS-4W1, were used in mono- and co-culture fermentations. The monocultures highlighted important species-specific differences in the metabolism of sugars and organic acids, while binary co-cultures demonstrated the roles played by bacteria and yeasts in the production of cellulose and typical volatile acidity. Aroma complexity and sensory perception were comparable between reconstructed (with the three strains) and native microbial consortia. This study provided a broad picture of the strains’ metabolic signatures, facilitating the standardization of kombucha production in order to obtain a product with desired characteristics by modulating strains presence or abundance.