Identification of microbiological risk factors and their control points in commercial black tea manufacture. A case study of Kenya tea development agency (KTDA) Githambo tea factory

Abstract

This study involved analysis of microbiological risk factors and their control points in commercial black tea manufacture at Githambo tea factory. The specific objectives were: 1) Determination of the levels of total viable counts, coliforms and Staphylococcus aureus in the raw material (fresh green tea leaves) and at the processing stages of withering, rolling, fermentation, firing/drying, sorting and packing; 2) Determination of the quality of water used for cleaning and soaking of oversized tea and its effects on total viable counts, coli forms and Staphylococcus aureus; 3) Determination of the hygiene status of equipment surfaces and utensils used in tea processing; and 4) Identification of the critical control points for identified microbiological hazards. Total viable counts (log of means/g) were highest at the reception (6.57), reduced after drying (4.50) but increased at packing (4.64). Faecal coliform counts (log mean MPN cells/g) increased from field (2.61) to maceration/rolling (3.49), reduced at drying (2.32), and finally increased at packing (3.58). Staphylococcus aureus counts (log of means/g) increased from the field (3.61), to the maximum at withering (5.47), then reduced at ferme~tation (4.82) and further at drying (l.83), but finally rose at packing (2.08). After drying, black tea underwent contamination in the sorting and packing sections. The most contaminated (expressed as log of total viable cells/em' ) factory equipments were scooping spades (4.47) and ball breakers (3.79) while the interior surfaces packing paper sacks(1.33) were the cleanest surfaces and were of expected microbiological quality (maximum of 102 cells/em"). The quality of water used in the factory was not potable i.e. did not comply with requirements of the Kenya Standard (KS 05-459) but this did not correlate with the microbiological quality of black tea (P< 0.01). Grading of black tea significantly affected its level of contamination (P< 0.05) with primary grades meeting the required microbiological quality while secondary grades were non-compliant. Microbiological hazards were therefore classified as risks posed by enteropathogenic microrganisms indicated by the presence of faecal coliforms and pathogenic Staphylococcus aureus. Drying/firing, sorting and packing processes were identified as a Critical Control Points (CCPs) for both categories of hazards. In order to enhance product safety, it is recommended that commercial tea processors adopt HACCP as a food safety management system. There is need to modify the tea processing machinery in order to eradicate tea spillages in all the sections especially the dry tea section. Further research is recommended to establish mechanisms of reduction Staphylococcus aureus by the fermentation process, effects of the withering and fermentation conditions on the likelihood of enterotoxin production by pathogenic Staphylococcus aureus and its fate after drying. There is a further need to establish the microbiological quality status of tea in the Kenyan retail market.