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 Eastern 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 results in extensive mould and bacterial growth. This leads to a product with inferior leaf colour and organoleptic quality as well as health concerns. Unlike during the manufacture of black tea, honeybush curing temperatures do not reach levels where these contaminants are eliminated. The microbial contaminants 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 during the curing of honeybush tea. YG and YpSs gave good results, while the Czapek medium was found to be unsatisfactory for the detection of microbial contaminants. A low pH (pH 5.0) favoured mould growth, while bacteria proliferated at pH 7.0. Honeybush material fermented in a curing heap and material fermented under controlled conditions at 40 and 50 °C showed microbial contamination, but no contaminants were detected on or in material fermented at higher temperatures (60, 70 and 80 °C). Two thermophilic moulds, Humicola grisea var thermoida and Humicola lanuginosa , a thermotolerant mould, Rhizomucor pusillus , and five endospore‐forming species of the genus Bacillus were isolated. The data indicated that R pusillus was the predominant microbial contaminant. © 1999 Society of Chemical Industry