Effect of storage on the quality of processed palm oil collected from local milling points within Ile-Ife, Osun State, Nigeria

The influence of storage practices on physicochemical and microbial changes in crude palm oil (CPO) from milling points in Ile-Ife, Nigeria were investigated. Freshly milled CPO samples were collected from four traditional milling points, dispensed in 150 mL portions in sterile bottles and stored under two different conditions (sunlight reflection and in the dark, both at room temperature) for 4 months. Samples were obtained periodically during the storage period for microbiological and physicochemical analysis following established methods. The aerobic mesophilic (2.16 × 106 cfu/mL) and Enteric bacterial (1.6 × 106 cfu/mL) counts of the fresh CPO samples decreased during storage with those exposed to sunlight reflections having very high significant difference (P < 0.00) compared to those stored in the dark at P ≤ 0.05. The bacterial isolates were identified as Bacillus pasteurii (29%), Staphylococcus aureus (22%), Enterobacter aerogenes (17%), Micrococcus sp. (12%), Escherichia coli (8%), Pseudomonas aeruginosa (7%) and Serratia marcescens (5%). Of the physicochemical parameters studied, moisture content (MC) reduced significantly from between 2.55 and 5.50% in fresh sample to between 0.1 and 0.5% at the end of storage while the free fatty acids (FFA) increased from between 0.5 and 1.0% to between 2.2 and 3.1% respectively. Storage under the influence of sunlight resulted in significant increase in iodine value of CPO from Mills 1, 2 and 4, indicating oxidative instability of the palm oil. It could be concluded that storage of freshly milled palm oil at room temperature (in the dark or exposure to sunlight) for a period of 4 months resulted in reduced bacterial load, decrease in MC and stable peroxide value and FFA.