Nutritional biotransformation in traditional fermented tea (Miang) from north Thailand and its impact on antioxidant and antimicrobial activities

Abstract

Miang is a traditional fermented tea made from fermentation of Assam tea leaves with mixed microbial culture involving lactic acid bacteria and yeast. Miang has important bioactive benefits such as antioxidant and antimicrobial activity with relevance to health benefits. Miang is categorized into two processes; filamentous fungi growth-based (FFP) and non-filamentous fungi-based (NFP) process, depending on area of production. Further, Miang is also divided into 2 types; astringent Miang and sour Miang, depending on fermentation time. The aim of this research was to determine the important macronutrient biotransformation of Miang diversity under above processes and types and explore the impact on bioactive compounds relevant to antioxidant and antimicrobial activities. During fermentation, pH, total acid, nutritional components, total polyphenols (TP), total tannins (TT), total flavonoids (TF), total catechins (TC), antioxidant activity and antimicrobial activity were evaluated. Miang when fermented for longer sour Miang process compared to shorter time astringent Miang increased crude protein, fiber, and ash contents whereas soluble carbohydrates decreased. Even though TP, TT, TF and TC of sour Miang was lower, the overall antioxidant activity was higher than astringent Miang. This suggests that in addition to the phenolic compounds, other specific phenolics and substances such as biotransformed protein and fat could contribute to antioxidant properties. Additionally, Miang also contains antimicrobial activities against dental caries pathogenic bacteria Streptococcus mutans, gastrointestinal disease causing Vibrio cholerae and Salmonella enterica serovar Typhimurium through likely effects of organic acids and phenolic compounds.

Tannin-tolerant and Extracellular Tannase Producing Bacillus Isolated from Traditional Fermented Tea Leaves and Their Probiotic Functional Properties

“…Some B. tequilensis and B. siamensis isolates showed high acid tolerance, bile salt tolerance, hydrophobicity and antimicrobial activity. Miang may also be considered a traditional fermented product with health-relevant functional benefits with antioxidant compounds such as high levels of phenolic acid and flavonoids [18], which are potentially biotransformed by tannase producing Bacillus spp. Moreover, due to the high numbers of Bacillus spp.…”

“…Until now, there have been few published reports on relevance of endospore-forming bacteria from Miang or other fermented tea leaves products. However, the number of endospore-forming bacteria which accounted for approximately 40-45% of total bacterial counts in 40 Miang samples collected from twenty producing locations were detected and therefore suggested that they play specific roles in Miang fermentation [18].…”

“…The useful therapeutic phenolic compounds which are related to the catechins and tannins were also found in Miang at higher concentrations when compared to fresh tea leaves, particularly in Miang made from young tea leaves [6]. Recent studies have also indicated the presence of endospore forming bacteria, which was significantly detected from 40 Miang samples in high numbers ranging from 40% to 50% of total bacterial counts [18]. Further understanding of this endospore forming species diversity of Bacillus isolated from Miang and other fermented tea and their metabolic role is essential for understanding the functional health benefits.…”

Solidago virgaurea L. Plant Extract Targeted against Candida albicans to Reduce Oral Microbial Biomass: A Double Blind Randomized Trial on Healthy Adults

“…Due to the chemical complexity of plant extracts, the exact role of major plant components or synergies between plant components still remains in question. However, several clinical studies demonstrated the efficacy of various herbal extracts to reduce plaque deposits and to improve oral conditions such as chronic gingivitis and post-operative dental surgery [39][40][41]44]. The review of literature revealed that vitamins and antioxidants of vegetal origin could interfere with inflammatory reaction, free radicals and endothelin in damaged periodontal tissues [17][18][19]48].…”

“…Main natural compounds described as antimicrobial compounds are essential oils (complex mix of terpenoids and phenylpropane derivatives (aromatic compounds)) and tannins (phenolic products that can precipitate proteins, such as escin) [37][38][39][40][41][42]. Some vegetal compounds display anti-inflammatory properties, such as vitamins, mineral elements (iron), proteases (papain and bromelain, a mix of acid proteases), or some flavonoids (close to tannins, such as baicalin) [41,[43][44][45][46]. Vitamins are essential organic substances that are required in small amounts to catalyze metabolic reactions [19].…”