Field Research for Production Method of Miang: Post-Fermented Tea in Thailand

Abstract

Miang" is a type of post-fermented tea in nor thern Thailand, which is produced by lactate fermentation. The fermentation process is similar to that of Awa-bancha, which is a type of Japanese post-fermented tea from Tokushima. However, the processing procedures for the Miang and Japanese post-fermented teas are different. Miang is classified into two types based on its fermentation period. Mian-Faat (astringent Miang) is produced after fermentation for several weeks to one month. Mian-Som (sour Miang) is produced after fermentation for several months. Additionally, a part of Miang production process includes fungal fermentation. In general, the leading process of Miang processing is lactate fermentation by lactic acid bacteria. Among the post-fermented teas, Miang has the highest production rate. However, most individual producers are small-scale produces. Although the basic procedure of Miang production is the same, certain details var y depending upon the production area and producers. Microbial control, par ticularly the control of lactic acid bacteria, in Miang production is extremely important for its stable and continuous production. However, in several cases, Miang production is based on individual experience. Recently, biodiversity of microorganisms was discovered. Therefore, understanding the Miang production in each production area is essential for the production of unique regional Miang.

Relationship between the Physiological Activity of Japanese Post-Fermented Teas and Lactic Acid Bacteria

“…The caffeine content in Ishizuchi-kurocha decreases after steaming. In one manufacturing lot of Ishizuchi-kurocha, the amount of caffeine in raw tea leaves was 6.5 g/100 g, while it was 2.7 g/100 g after steaming and 3.5 g/100 g after primary fermentation and 3.3 g/100 g after secondary fermentation [2]. Caffeine is derived from raw tea leaves, as no decrease in caffeine is observed even after fermentation compared to tea leaves before fermentation.…”

“…Batabata-cha from Toyama is produced by fermentation with fungi belonging to the genus Aspergillus [1]. The production of the other three Japanese post-fermented teas from Shikoku involve lactate fermentation by lactic acid bacteria [2]. The production method common to several post-fermented teas is heating the tea leaves by steaming or boiling them to sterilize and inactivate the enzymes and then growing microorganisms in the tea leaves to change the tea leaf components.…”

“…By contrast, Southeast Asian post-fermented tea is produced without drying the leaves. In Japanese post-fermented tea, changes in the components of tea leaves caused by microorganisms cease during the drying process [2]. Conversely, in the case of the post-fermented tea from Southeast Asia, the composition of tea leaves continues to change during distribution.…”

Diversity of Lactic Acid Bacteria Involved in the Fermentation of Awa-bancha

“…Post-fermented tea is only produced in a limited area of the world. In Asia, the aerobically fermented type is made in China for Pu’er tea ( Guo et al , 2004 ), while anaerobically fermented tea is produced in Thailand ( Horie et al , 2020 ) and Myanmar for Laphetso ( Fukushiyama and Tain, 2009 ). Four types of post-fermented tea are produced in Japan.…”

“…Awa-bancha is an anaerobically fermented tea, and no other tea in Japan is made in a similar manner. Its production method is similar to that of Miang in Thailand ( Horie et al , 2020 ). Awa-bancha is primarily produced between July and September.…”