Abstract

Introduction: Peeling is one of the most important steps in pistachio processing. Optimizing the peeling step can improve the quality of the finished product. Materials and Methods: In this research, the technical function of two kinds of peeling machine (screw-blade and screw) and the manual peeling method were evaluated. The tested pistachio was Fandoghi in the ripening stage. The samples were peeled, the number of fully-peeled, partially-peeled, unpeeled, and broken nuts were counted, and the percentage of each one was determined. Then, the changes in peroxide value, shell and kernel color, texture, and sensory properties (taste, color, texture, and overall acceptance) were evaluated at different intervals of 0, 1, 2, 3, and 4 months. The experiment was conducted in a completely randomized design with the factorial arrangement. Results: The results showed that the high percentage of fully-peeled nuts (87.95%) belonged to the screw-blade method. The percentage of partiallypeeled and broken nuts in the screw method was more comparable with the screw-blade machine. There was no considerable difference in the screw and screw-blade methods in terms of peroxide value. The manual peeling method was better in color attributes (L*, a*, b*) compared with screw-blade and screw methods. The highest taste, color, and overall acceptance rate belonged to the manual peeling method, showing a big difference from the other methods. The quality of color in the screw-blade method was more than that in the screw method. Conclusion: In general, the screw-blade method is suggested to be used for peeling pistachio nuts.