Microbiology and Nutritional Quality of Stored Soya Oil

摘要

Soyabean cultivars 1681-3f, 1740-2F, 1448-2F and 1440-1E were obtained from the Seed Health Unit of the International Institute of Tropical Agriculture (IITA) Ibadan Oyo State, Nigeria. The microbiology and nutritional qualities of the extracted stored soyaoil at 29±2°C in January, 2006 and at 23±2°C in June, 2006 were investigated. Seven microorganisms were isolated from the soyaoil samples when stored for 4 weeks, at which time the oil samples had gone rancid with offensive odour. The bacterial isolates include Bacillus subtilis and Staphylococcus aureus, while the fungi isolated were Aspergillus flavus, A. fumigatus, A. niger, Fusarium poae and Rhizepus oryzae. The total microbial viable counts decreased in the order of 1681-3F soya oil >1440-1E soy oil>1740-2F soy oil>1448-2f soya oil > refined soya oil, respectively. Physicochemical analysis of the soya oil revealed significant increases (p = 0.05) in the percentage of free fatty acid and peroxide value both in January and June 2006. The iodine value also increased significantly (p = 0.05) in January, but decreased in June. On the other hand, the moisture content increased significantly (p = 0.05) in the month of June but decrease in January. Soya oil samples are therefore, better stored in the month of January than June. Aflatoxin was not detected in any of the oil samples, despite the isolation of A. falvus.