Physical Properties of Pistachio Nuts

Abstract

Physical properties of pistachio nuts were evaluated to determine distinguishable characteristics of early split pistachio nuts. The hulls of early split pistachios abnormally split open several weeks before harvest, making the kernel more vulnerable to the aflatoxin producing mold Aspergillus flavus. The most distinguishing features of early split pistachio nuts were found to be shell staining and hull adhesion tendencies. Using shell stain characteristics and shell dimensions, an algorithm was developed that correctly classified 90% of the early splits, and 97% of the normal nuts. When unhulled nuts were placed into a tumbler, 98% of the early split nuts kept their hulls while 95% of the normal nuts were hulled. A mechanical separation device was constructed that successfully separated 90% of the early split nuts and only 5% of the nonsplit nuts from the rest of the samples. Nut mass, length, width, and height are significantly different between early split nuts and normal nuts, however, these properties cannot be used to accurately classify the nuts into split types.