The effects of roasting on oxidative stability of pistachio nut kernels at accelerated conditions

Pistachio nut (Pistacia vera L.) is one of the most delicious and nutritious nuts in the world. Roasting process enhances the flavor, color and texture of pistachio nuts and increase overall palatability of the valued products. Oxidative stability is also an important parameter for the quality assessment of pistachio nuts. The main objective of this study is to determine the effect of roasting on oxidative stability , color changes of pistachio samples. For this purpose, pistachio kernels were roasted with two steps industrial roaster at different temperature; 110-120, 130-140, 150-160° C. Rancimat Method, which is one of the Accelerated Shelf – Life Test (ASLT) method, was used to determine the oxidative stability of raw and roasted pistachio nut kernel oil. The induction time (IT) of raw and roasted pistachio samples were automatically recorded at 100, 110, and 120°C. As the temperature increased induction time was significantly decreased during ASLT (p<0.05). The roasted pistachio sample has higher IT than IT of raw pistachio sample. Although increasing the oxidative stability with increasing roasting temperature, very high roasting temperature (150-160°C) decreased IT. The color measurements of pistachio kernel are performed using HunterLab ColorFlex. L* and b* values were significantly decreased with roasting (p<0.05), whereas a* value was significantly increased due to roasting (p<0.05). As a result, roasting of pistachio nuts improved the oxidative stability of the nut. Key Words: Pistachio nut, roasting, oxidative stability, Rancimat method, color