Effect of Variety on the Quality Parameters of Crude Soybean Oil

Abstract

The main objective of this study was to evaluate the effect of seed variety on soybean oil quality and quantity. Soybean oil was extracted from four different varieties obtained from three locations in Nigeria namely; Benue, Bauchi and Kaduna States. The soybean seeds were sorted, cracked, conditioned, flaked and pressed to obtain the oil. The oil was further treated with 2% distilled water to obtain the degummed oil. The oil samples were investigated for their physical, chemical and mineral contents. The physical parameters showed that the oil yield ranged between 22.79 and 24.79%, specific gravity was from 0.91 to 0.93, density 0.92 to 0.94g/m3, refractive index 1.46 to 1.47 and smoke point 230.50 to 233.50°C. Chemical analysis result showed that free fatty acid ranged from 0.28 to 0.29% with sample B (spotted variegated variety) as the lowest, peroxide value 1.77 to 1.88 meq/kg with sample D (black variety) having the highest value, saponification value ranged between 194.12 and 194.88 mgKOH/g, iodine value ranged from 104.83 to 105.07mg/100g while phosphatide ranged from 2.65 to 3.10 with sample D (black colour) having the highest value. All the chemical parameters showed no significant differences (p<0.05) except peroxide and phosphatide values. The mineral composition of the oil samples showed that Calcium ranged from 3.33 to 3.66mg/kg, Iron was from 0.23 to 0.27mg/kg, Magnesium 0.73 to 0.75mg/kg while Manganese ranged from 0.005 to 0.010mg/kg. The study revealed that soybean variety had an effect on the oil yield, specific gravity, density, color intensity, peroxide value and calcium content of the oil samples. The refractive index, peroxide value, saponification value, iodine value and iron content of the oil samples were within the permissible limits stipulated by CODEX (1999) and the National Agency for Food and Drug Administration and Control (NAFDAC) (2019). These quality indicators are important parameters for choosing soybean variety for industrial and domestic oil production.