ASPERGILLUS MOLDS AND AFLATOXINS IN PISTACHIO NUTS IN CALIFORNIA

A total of 14 Aspergillus species were isolated from the kernels of pi stachio nuts, mainly early splits, from 11 commercial orchards in Cali fornia in 1991 and 1992. Early splits are atypical nuts that have spli t hulls, exposing the kernel to invasion by molds and insects (normal nuts have intact hulls). A. niger was the only Aspergillus species tha t occurred frequently (in 30% of kernels from early splits). However, A. flavus or A. parasiticus (potential producers of the mycotoxins afl atoxins) were found in early splits from most orchards, and A. ochrace us or A. melleus (potential producers of the mycotoxins ochratoxins) w ere found in all orchards. Aflatoxins were detected in early splits fr om six of nine orchards in 1991 and five of eight orchards in 1992. Ea rly splits with rough, shriveled hulls had more than twice the A. nige r infection and more than three times as much A. flavus or A. parasiti cus infection as early splits with smooth hulls. The rough early split s had over 99% of all the aflatoxins detected. Kernels infested by the insect navel orangeworm (Amyelois transitella) had substantially more infections by A. niger, A. flavus or A. parasiticus, and A. ochraceus or A. melleus and had 84% of all aflatoxin detected. The hulls of ear ly splits frequently had low levels of aflatoxin. Hull rupture due to damage by birds or to cracking resulted in kernels infected with Asper gillus molds but at low levels. Fortunately, the pistachio nuts most l ikely to have mold and aflatoxin contamination, rough early splits inf ested with navel orangeworm, had several physical characteristics (wei ght, size, shell discoloration, hull appearance) distinct from normal nuts that could facilitate removal during processing.