Isolation of Food Pathogens From Freshly Milled Palm Oil and the Effect of Sterilization on Oil Quality Parameters

摘要

The isolation and identification of food pathogens from freshly milled palm oil as well as the effect of steam sterilization on some quality parameters of palm oil was evaluated. Microbial isolations and quality parameters were carried out at day 0, day 14 and day 28. Biochemical parameters such as Peroxide value, Anisidine value, Free fatty acid, Deterioration of bleachibility index (DOBI) and Carotene value was analyzed in the same samples using the digital Palmoiltester. The most frequently isolated bacteria from the unsterilized samples were Pseudomonas aerugenosa, Bacillus subtilis, Enterococcus aerogenes, Staphylococcus saprophyticus and Micrococcus varians while the most frequently isolated fungal species were Aspergillus niger aggregate (IMI number 503810), Cochliobolus sp. (anamorphic state: Curvularia) (IMI number 503811), Penicillium citrinum (IMI number 503812) and a yeast, Meyerozyma guilliermondii (IMI number 503813). The fungal count in the unsterilized samples from day 0 to day 28 was in the range of 2.17 x 103 to 5.0x106 while the bacteria count ranged from 4.08 x 102 to 9.0x 108. The sterilized sample showed no microbial contamination throughout the 28 day storage. However, sterilization caused significant changes when compared with unsterilized sample as thus; significant (p<0.05) increases in peroxide value of up to 5.14% and 15.99% after the 14th and 28th day respectively, significant (p<0.05) increases in anisidine value of up to 170% and 200% for day 14 and day 28 respectively, significant (p<0.05) decreases in carotene content of up to 11.84% and 15.79% for day 14 and day 28 respectively, significant (p 0.05) changes in free fatty acids.