Maitshwarelo Ignatius Matsheka*, Clement Chedza Magwamba, Sisai Mpuchane and Berhanu Abegaz Gashe
The microbial quality and predominant bacterial groups of three fermented beverages was investigated. The bacteria associated with sorghum beer, sour milk (madila/amasi) and sour maize beverage (mageu/mahewu) were determined using standard microbiological techniques. The predominant microorganisms were screened for the production of four biogenic amines using decarboxylase broth. Sorghum beer had the highest bacterial counts with sour maize beverage having the least bacterial counts. Hafnia alvei isolated from sour milk was found to be a major histamine and putrescine producer with 21.2 and 17.56 mg/100 ml respectively. On the other hand, the most important cadaverine producers were Pantoea citrea and Hafnia alvei with19.27 and 18.75 mg/100 mlrespectively. Enterococcus faecium and Enterococcus faecalis isolated from sour milk were found to be prolific tyramine producers with 35.5 and 20.07 mg/100 ml respectively. The Bacillus species isolated from all fermented food products were found to be weak histamine producers. The study also revealed that production of biogenic amines was not a widely distributed property among the lactic acid bacteria as previously documented for other fermented food products. Based on the results, it was concluded that sour maize beverage was the safest fermented food product in terms of the microbial quality and presence of biogenic amine producing bacteria.
Key words: Biogenic amines, biogenic acid producing bacteria, fermented beverages, decarboxylase activity, histamine, lactic acid bacteria