Natural additives effects on some quality parameters of un-refined peanut oil

Abstract

Edible oils are widely utilized in diets as a major source of fat and a heat transfer medium during frying. Improvement on nutritive value is a major concern in edible oil industry. Therefore, objectives of this work were to investigate the effects of sweet pepper (Capsicum annuum) and tomato fruit (Lycopersicon esculentum.) as additives on some physical and functional properties, nutritive values and stability of peanut (Arachis hypogaea) oil. Response surface methodology was employed to study effect of natural additives on peanut oil. The variables were additives ratio (5:0, 3:2, 2.5:2.5, 2:3, 0:5) of sweet pepper: tomato and incubation time (1, 1.5, 2.5, 4, 6 hrs). While the responses were oil iodine value, peroxide value, free fatty acid, saponification value, colour, viscosity, beta-carotene, vitamin E and vitamin K. The calculated means for iodine value, peroxide value, free fatty acid, saponification value, colour, viscosity, β-carotene, vitamin E and vitamin K were 105.39 ± 10.38 Wijs, 9.89 ± 2.81 mEqkg^-1, 2.4 ± 1.13%, 166.1 ± 20.53 mgKOH/g, 0.16 ± 0.2 A, 0.02 ± 0.00 Nsm^-2, 788.3 ± 69.50 μg/100g, 12.7 ± 0.87μg/100g and 7.8 ± 0.59 μg/100g, respectively. Coefficient of determination (R²) of models for iodine value, peroxide value, free fatty acid, colour, viscosity, β-carotene and vitamin E were 0.76, 0.91, 0.76, 0.89, 0.93, 0.97 and 0.84, respectively. Functional properties of the oil including iodine value and saponification value reacted differently to treatment. Iodine value was significantly (p<0.05) influenced while non-significant (p>0.05) effect was recorded for the saponification value. The treatments significantly (p<0.05) influence peroxide value and free fatty acid of the extracted oil. Physical properties of the peanut oil measured by colour and viscosity were significantly influenced by the treatment (p<0.05). Nutritive values of the peanut oil which were beta-carotene and Vitamin E were significantly (p<0.05) influenced by the treatments but Vitamin K was not significantly influenced.

Keywords: Peanut, Additives, Oil, Stability, Properties

African Journal of Food, Agriculture, Nutrition and Development, Volume 12 No. 6