Miang is comprised of non-salted, fermented or pickled tea leaves
that are traditionally produced in the mountainous areas of the northern
Thailand (Kawakami et al., 1987; Okada et al., 1986). Fresh tea
leaves of Camellia sinensis var. assamica are conventionally used as the
raw material for Miang fermentation. This tea plant is commonly called
“Miang tree” by northern Thai people and it can be found throughout
Chiang Mai Province as well as in other upper northern provinces of
Thailand, including Lampang, Chiang Rai, Phayao, Nan and Phrae with
elevations as high as 450–1500 m above sea level. However, the tea
plant is most commonly found at heights of 600–1000 m above sea
level (Korsamphan et al., 2010). Miang is different from other
fermented tea leaves, such as Kombucha, because the fermentation
occurs simultaneously without the addition of sugars, and it is consumed
by being eaten or chewed. It is made by natural fermentation
and is processed for a week or up to one year without the use of any
preservatives, such as sodium chloride. The fermented product is soft
and has a bitter taste that is either astringent or sour. Consequently,
Miang is often classified by local people of northern Thailand as either
astringent Miang or sour Miang; however, no exact criteria have been
established for the purposes of classification. Miang producers typically
classify it by the fermentation time and the taste of Miang. The chewing
of Miang is specific to northern Thai consumers where Miang is
frequently consumed after meals. Moreover, Miang is commonly served
at all types of ceremonial occasions by the northern Thai people
(Gypmantasiri et al., 2001).
Tea leaves contain significant amounts of tannins that are considered
an inhibitor of certain microorganisms (Bhat et al., 1998). Thus,
microorganisms associated with the fermentation of Miang, as well as
the living microorganisms in Miang, are of significant investigative
interest because they are able to survive in the tannin-rich substrate.
Commonly known as a group of key microorganisms, lactic acid bacteria
play an important role in Miang fermentation. The first reporting of the
presence of Lactobacillus plantarum in Miang gained interest in a number
of studies for its role in the bacterial flora formation involved with
Miang fermentation (Okada et al., 1986). However, in the last several
decades, L. pentosus, L. vaccinostercus, Lactobacillus sp., Enterococcus
casseliflavus and Enterococcus sp. have been reported to be involved
with Miang fermentation. In 2007, research studies demonstrated
the involvement of E. calmelliae, L. thailandensis, L. camelliae and
Pediococcus siamensis in Miang fermentation (Sukontasing et al., 2007;
Tanasupawat et al., 2007). However, studies on the yeast that has
been isolated from Miang have lacked information concerning the relevant
biological communities and their impacts on tea-leaf fermentation.