Abstract

Bottled raphia palm wine was cultured in a laboratory medium amended with 0.5% acetic acid (pH 4.8). Two cultures of identified heat resistant yeast (HRY) and one unidentified yeast species were isolated. Cultures of the isolates grown on potato dextrose agar for 10 days at 26°C, survived pasteurization temperature at 80°C for 20 min and 85°C for 15 min. Of these HRY identified were Byssochlamys nivea,Byssochlamys zollerniae and one unidentified yeast species. To determine the source of contamination, fresh un-pasteurized Raphia palm wine was cultured. Result revealed that, colonies of the three HRY were higher compared with the pasteurized Raphia palm wine. Frequencies of occurrence at 80°C, 85°C and in un-pasterurized raphia palm wine were B. nivea 15.2, 6.1 and 24.2%; B. zollerniae6.1, 3.0 and 12% and yeast species 9.1, 6.1 and 18.2% respectively. The thermal destruction time were B. nivea 90°C for 15 min, B. zollerniae 90°C for 5 min and yeast species 90°C for 10 min. The result indicates they are acid tolerant and thermophilic yeasts with B. nivea having the highest frequency of occurrence.

Key words: Culture, pasteurization, spoilage, identification, thermophilic.