Effect of Infrared Roasting Process on the Microorganism Contaminations of Long and Round Iranian Pistachio Kernels

In this paper, the effect of infrared (IR) roasting conditions on Aflatoxins and total counts of two types of Iranian pistachio kernels, long and round, was studied. The optimized roasting conditions, 70 V for round pistachios and 90 V for long pistachios with 10 cm distance from IR source were used. Naturally Aflatoxin-contaminated kernels were supplied and roasted. Microbiological and Aflatoxins tests were done before and after roasting, and the results were analyzed by t-test at 5% confidence level. It was shown that 64.00% of total Aflatoxins and 63.99% of Aflatoxin B1 were reduced in long roasted pistachio nut kernels after IR-roasting. However, the reduction levels were 71.40% and 64.94% for total Aflatoxins and Aflatoxin B1 in round pistachio kernels, respectively. Total counts reduction was 99.99% in the round and 99.97% in the long pistachio kernels. In addition, mold and yeast numbers were reduced 99.99% in the round and 99.97% in the long pistachio kernels. Considering mild conditions (90°C and 11.5 min) in IR-roasting process, considerable amounts of reduction in bacteria, mold, and yeast, and the most important reduction of Aflatoxins. This research has shown that IR-roasting process can be considered as an effective method for pistachio nut roasting in Aflatoxin contamination reduction.