Extending African walnut oil (Tetracarpidium conophorum) shelf-life by blending it with palm, groundnut and avocado oils and study of their oxidative stability during accelerated storage

Abstract

Oils rich in polyunsaturated fatty acids are beneficial for health. However, their high content in polyunsaturated fatty acids makes them unstable during processing which limit their application. In the food industry, hydrogenation and the addition of antioxidants are used to extend their shelf-life. However, hydrogenation leads to trans fatty acid which promote coronary heart disease, and synthetic antioxidant has been reported to be related to cardiovascular diseases, cancer etc. As solution, researchers have been looking for natural ways to preserve oils and fats by blending less stable with more stable ones or by using natural antioxidants. The objective of this study was to extend African walnut oil shelf life by blending it with palm oil, groundnut oil, avocado oil which are more stable. Palm, groundnut, African walnut and avocado oils were obtained through mechanical cold press method. Multisource edible oils were formulated using the binary model. The blends were prepared following the ratios 50:50, 60:40 and 70:30 (Palm oil/groundnut oil/avocado oil: African walnut oil). Each of the oils involved was also used at 100 %. The samples were initially tested for their initial quality and stored at 65 °C for 21 days, 8 h heating daily. Samples were withdrawn after every 7 days for analysis, by determining their peroxide, p-anisidine, TOTOX, thiobarbituric and acid values. Results showed that all the tested oil were of good quality. African walnut oil 100 % was the most altered in terms of the presence of free fatty acids, primary and secondary oxidation products compared to the other oils samples and their blends. Africa walnut oil shelf life can be extended by blending it with Palm oil, Avocado oil or Groundnut oil.