Identification of microbial contaminants present during the curing of honeybush tea (Cyclopia)

Honeybush tea (Cyclopia) is produced over a wide area of the Western and Ea stern Provinces of South Africa and exported to several countries worldwide . It is traditionally manufactured by curing honeybush material for several days at relatively high temperatures and moisture contents and this result s in extensive mould and bacterial growth. This leads to a product with inf erior leaf colour and organoleptic quality as well as health concerns. Unli ke during the manufacture of black tea, honeybush curing temperatures do no t reach levels where these contaminants are eliminated. The microbial conta minants and the minimum temperatures necessary to eliminate these organisms were thus investigated. Yeast-Glucose (YG), Yeast-Starch (YpSs) and Czapek media were evaluated for the isolation of contaminants that developed duri ng the curing of honeybush tea. YG and YpSs gave good results, while the Cz apek medium was found to be unsatisfactory for the detection of microbial c ontaminants. A low pH (pH 5.0) favoured mould growth, while bacteria prolif erated at pH 7.0. Honeybush material fermented in a curing heap and materia l fermented under controlled conditions at 40 and 50 degrees C showed micro bial contamination, but no contaminants were detected on or in material fer mented at higher temperatures (60, 70 and 80 degrees C). Two thermophilic m oulds, Humicola grisea var thermoida and Humicola lanuginosa, a thermotoler ant mould, Rhizomucor pusillus, and five endospore-forming species of the g enus Bacillus were isolated. The data indicated that R pusillus was the pre dominant microbial contaminant. (C) 1999 Society of Chemical Industry.