EFFECTS OF STORAGE CONDITIONS AND PACKAGING MATERIALS ON THE PHYSICOCHEMICAL PROPERTIES OF PALM OIL

Abstract

This study was carried out to evaluate palm oil storage stability in four packaging materials commonly usedinNigeria, under three storage conditions. Freshly produced palm oil was purchased, filled in these packaging materials namely: metal cans, white plastics, glass bottles and pet bottles and stored in direct sunlight (35±1°C), ambient temperature (27±1°C) and refrigerator (5±1°C) for 120 days. Physicochemical properties, such as melting point, flash point, specific gravity, refractive index, colour, peroxide value, acid value, iodine value, saponification value and free fatty acid content were determined. Also determined were the vitamin A and E in each of the samples in every 30 days using standard methods. The results of the physicochemical properties of samples stored in direct sunlight, showed that all the samples stored under this storage condition were adversely affected by sunlight as the peroxide values increased from 0.61-23.18meq/kg, 0.61-10.10 meq/kg, 0.62-13.60 meq/kg and 0.61-15.41 meq/kg. The acid values increased significantly from 9.92-308.10 mg/KOH/g, 9.88-132.24 mg/KOH/g, 9.94-160.16 mg/KOH/g and 9.90-157.84 mg/KOH/g. The free fatty acid also increased in values from 4.96-154.05%palmitic acid, 4.94-66.12 % palmitic acid, 4.97-80.08 % palmitic acid and 4.95-78.92%palmitic. The saponification values increased from 10.21-274.76 mg/g, 10.21-111.07 mg/g, 10.22-148.50 mg/g and 10.21-170.11 mg/g. However, the iodine values decreased from 10.93-0.00 g/g, 10.92-0.02 g/g, 10.92-0.00 g/g, and 10.92-0.00g/g for metal can, white plastic, glass bottle and pet bottle respectively. The results of the physicochemical properties of samples stored inside a closed wooden cupboard showed that, most of the samples stored under this condition were still in fairly good condition as the peroxide values increased from 0.61-16.21 meq/kg, 0.61-5.07 meq/kg, 0.62-7.88 meq/kg and 0.61-8.28 meq/kg. The acid values also increased from 9.92-197.30 mg/KOH/g, 9.88-72.44 mg/KOH/g, 9.94-139.42 mg/KOH/g and 9.90-124.64mg/KOH/g. Free fatty acid increased from 4.96-98.65 % palmitic acid, 4.94-36.22 % palmitic acid, 4.97-69.71 % palmitic acid and 4.95-62.32 % palmitic acid. Saponification values increased from 10.21-141.21 mg/g, 10.21-55.08 mg/g, 10.22-64.05 mg/g and 10.21-96.15 mg/g. While, the iodine values decreased from 10.93-0.00 g/g, 10.92-1.50 g/g, 10.92-1.01g/g and 10.92-0.10 g/gfor metal can, white plastic, glass bottle and pet bottle respectively. The results of the physicochemical properties of the samples stored in the refrigerator showed that all the samples stored under this condition were still wholesome for consumption, as the peroxide values were slightly increased from 0.61-6.17 meq/kg, 0.61-3.12 meq/kg, 0.62-3.91 meq/kg and 0.62-5.08 meq/kg. Acid values increased from 9.92-88.48 mg/KOH/g, 9.88-31.54 mg/KOH/g, 9.94-75.84 mg/KOH/g and 9.90-68.30 mg/KOH/g.Free fatty acid increased from 4.96-44.24 % palmitic acid, 4.94-15.77 % palmitic acid, 4.97-37.92 % palmitic acid and 4.95-34.15 % palmitic acid. Saponification values increased from 10.21-105.10 mg/g, 10.21-36.05 mg/g, 10.22-51.77 mg/g and 10.21-69.44 mg/g. Iodine values decreased from 10.93-1.04 g/g, 10.92-3.09 g/g, 10.92-1.95 g/g and 10.92-1.27 g/gfor metal can, white plastic, glass bottle and pet bottle respectively. Hence palm oil is best preserved under refrigerating condition and in white plastic container.