Yeast and mould contaminants of vegetable oils

Six vegetable oils were examined for their yeast and mould contaminants. Sixteen yeasts and 35 mould species were isolated from the oil samples. The isolates were members of the following genera: Saccharomyces, Candida, Debaromyces, Hansenula, Trichosporon, Torulopsis and Pichia for yeasts and Aspergillus, Fusarium, Penicillium, Mucor, Geotrichum and Cladosporium for moulds. Amongst the two groups of fungi, Saccharomyces and Aspergillus species predominated. Examination of the oils for their physico-chemical characteristics revealed that their moisture contents were generally below 1%. Palm oil had the highest biochemical oxygen demand (BOD, 2576.88 ± 12.37 mg/l), while palm kernel oil had the lowest (450.25 ± 7.42 mg/l). Palm oil had the highest iodine value (40.32 ± 0.27) and coconut oil the lowest (13.18 ± 0.22). The cumulative maximum growths of the yeast and mould species on the oils were used to determine the stabilities of the oils to biodeterioration. Results indicated that palm kernel oil was the most stable to fungal deterioration, while palm oil was the least biostable.