Microbial distribution and contamination in black tea

Microbial contamination, distribution pattern, population density of microorganism in tea infusion prepared from
262 black tea samples were analysed consecutively for a period of seven years from 2011 to 2017. Surprisingly, most
of the tea samples were contaminated with various microorganisms like E. coli, Salmonella sp., molds etc. Tea
samples were received from tea estates of Upper Assam, South Bank and North Bank regions predominantly in peak
growing season (summer) and in back end crop (winter season). The standard plate count (SPC) technique was
followed to assess the microbial load such as total plate count (TPC), yeast and mold populations and intestinal
enterobacteria like Escherichia coli and Salmonella sp. Intestinal microorganism, E. coli and Salmonella sp. were
not detected in any of the tea samples of the three regions till 2015 whereas mold population and other microbes were
abundant on total plate count. Contamination of E. coli and Salmonella sp. was detected along with other microorganisms
in the tea samples analysed during 2016 and 2017. However, the per cent distribution of E.coli was the least while
total plate count was highest followed by mold and Salmonella sp. Contamination of black tea may occurs from
various sources like field contaminated tea leaves, careless handling of tea leaves in field and trough house, use of
contaminated water for washing machineries and factory floor, roaming of so many workers in and around the factory
premises etc. The growth of microorganisms in those areas is also induced by conductive atmosphere like temperature
and high humidity. Therefore, multiple efforts are necessary to keep the made tea contamination free.