The Relationship Between Date of Hull Splitting and Decay of Pistachio Nuts byAspergillusSpecies

Abstract

Atypical pistachio (Pistacia vera) nuts that have split hulls, known as early splits, frequently have kernels decayed by Aspergillus spp. In 1992 and 1993 pistachio nuts that had split hulls were marked in commercial orchards at approximately 2-week intervals. Depending on the orchard, 15 to 48% of the early splits had formed more than 4 weeks before harvest and 10 to 30% formed within 2 weeks before harvest. At harvest these nuts were also evaluated for kernel decay, insect infestation, and several physical characteristics. The incidence of decay caused by Aspergillus spp. (predominantly Aspergillus niger) was three times greater in the oldest early splits than in early splits formed in the period before harvest (no decay was found in normal nuts with nonsplit hulls). The oldest early splits also had the most shriveled hulls, which is a feature associated with aflatoxin contamination. At harvest the oldest early splits had less fruit fresh weight, lower kernel moisture, smaller shells, and more shell discoloration compared with early splits formed in the period before harvest and with normal nuts. These characteristics could be used to remove decayed nuts during processing.