Evaluation of Two Common Dryers on Physicochemical, Microbial and Sensory Characteristics of Pistachio during Storage

Drying is one of the most important stages of pistachio processing. The aim of this study was to investigate two common types of dryers available in Rafsanjan with emphasis on health related aspects. Fresh pistachio cultivars of Fandoghi were harvested from Rafsanjan gardens and the pistachio samples were dried after peeling and washing using Silage and Wagon dryers.

After drying, pistachio cultivars of Fandoghi were tested for 0, 1.5 and 3 months at room temperature (20 ± 2 ºC). Moisture content, peroxide value, conjugated dienes and conjugated triene, mold and yeast count were measured with three replicates. The experiment was conducted as a factorial experiment in a completely randomized design with three replications.

Peroxide value of dried pistachio samples in two drying machines were in the permissible range (less than 1 millequivalent /kilogram). Silage dryer samples showed less peroxide value, conjugated dienes and conjugated trienes than wagon dryer samples. At the end of the three-month period, the growth rate of mold and yeast in pistachio samples dried using wagon dryer decreased and their growth rate was less than the permissible limit (less than 1000 cell forming unit/gram).

Mold and yeast growth were not observed in dried pistachio samples using silage dryer. It is recommended to use more silage dryer in pistachio processing units.