Microbial distribution and contamination in black tea

Abstract

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.

Keywords: Black tea, intestinal enterobacteria, microbial load, pesticides, population density, standard plate count.