Evaluation of Oxidative Stability and Shelf-life Prediction of Pistachio Oil Using Rancimat

Rancimat is an automated technique to rapidly determine oxidative stability of fats and oils, which can also provide relatively good results regarding shelf-life prediction of the lipid system. In this research, the oxidative stability of different types of pistachio oil (wild and domesticated species) by using rancimat and the influences of chemical properties of pistachio oil on oxidative stability were determined.
The present study is a laboratory study. Oils of five pistachio varieties (including Bane, Ahmadaghaie, Kalleghouchi, Akbari, and Fandoghi) were extracted by solvent. The fatty acid profile of the pistachio oil was determined by gas chromatography, and chemical methods were used to measure the amount of antioxidants and oil quality indicators. Oxidative stability was determined by Rancimat. The mean values were compared using MStatC 2.10 software and based on the Duncan’s test at the level of 5%.
Oleic Acid and Palmitic Acid were the most representatives of total fatty acid and saturated fatty acids (SFAs) in pistachio oil, respectively. The highest percentage of oleic acid was observed in Ahmadaghaie variety and the highest and lowest percentage of mono unsaturated fatty acids (MUFA) and poly unsaturated fatty acids (PUFA) were observed in Bane Hull Oil (65%, 7.9%) and the lowest and highest percentage of MUFA and PUFA were observed in Bane Kernel Oil (53%, 32.8%). The highest Oxidative Stability Index was found in Bane Hull Oil (BHO), Bane Kernel Oil (BKO) and Ahmadaghaie oil, respectively. Activation energy was evaluated in the range of 92 to 98.2 kj/mol. The results showed that shelf-life of BHO, BKO and Ahmadaghaieoil were 786, 386 and 280 days at 25 ⁰C, respectively. Ahmadaghaie shelf-life was over 1.5 times more than those of the other commercial varieties.
Fatty acid composition and amount of antioxidants were the most important factors on oxidative stability of the pistachio oil and the cause of higher shelf-life of oil of wild pistachio types rather than the other commercial varieties. Among the domesticated species of pistachio, Ahmadaghaie variety is suitable for oil extraction and high thermal processes such as roasting.