Comparative Study of the Physicochemical Properties of Some Refined Vegetable Oils Sold in Mile One Market and Some Departmental Stores in Port Harcourt, Rivers State, Nigeria

Abstract

Physiochemical properties of some brands of edible oils (namely:- Turkey, Grand, Gino, tropical, Power, Mammador, local vegetable oil and kuli-kuli (raw/locally extracted groundnut oil)  sold in mile 1 market, Everyday supermarket and Next-time supermarket in Port Harcourt, Rivers state were studied to determine their quality and compare the results with some standards. All the oils were characterized for flash point, cloud point, iodine value, saponification value, unsaponifiable matter, acid value and peroxide value using standard methods of analysis. The results obtained show that the free fatty acid contents of the local and kuli-kuli oils were higher (0.709 and 1.96 respectively) than the maximum recommended value of 0.3 by SON and NIS while other brands were within the range. The measured moisture content values for Turkey, Grand, Gino and Mammador were higher than the standard range of 0.05 in the samples from Mile 1 market and in some supermarkets. Specific gravity, melting point, and cloud point were satisfactory except for Grand that showed a different cloud point of less than 2. Iodine value for the local oil is 20.25 (Wij’s) indicating the predominance of lauric acid while that of kuli-kuli (94.6 Wij’s) suggests the predominance of Oleic acid. The other brands showed iodine value of 46-50 Wij’s which indicates predominance of palmitic acid except the Grand oil that had the highest value of 125-128 (Wij’s). Saponification values and unsaponifiable matter were within the standard range of saponification value (245- 255) and unsaponifiable matter (0.1-0.15) for all the brands. Acid and Peroxide values of all the brands showed results within the standard. These results of the measured parameters show that the oils sold in the supermarkets are better protected from light induced oxidation (photoxidation) than those sold in open markets. 

Keywords: Flash point, Cloud point, Iodine value, Saponification value, Unsaponifiable matter, Acid value, Peroxide value, Photoxidation, Hydroperoxide and Light.