Purpose: The objectives of this research were to develop a sequential infrared and hot air (SIRHA) drying method for pistachios and evaluate its effectiveness to perform simultaneous drying and decontamination of pistachios.
Methods: Dehulled and sorted pistachios obtained from the Central Valley of California were dried in the SIRHA dryer using different combinations of time, and Infrared (IR) radiation and hot air drying to determine the optimum drying conditions. Pistachios were inoculated with Pediococcus and dried using the SIRHA dryer to evaluate the decontamination effect of SIRHA method.
Results: The results showed that the SIRHA drying of pistachios (IR heating for 2 h at a product temperature of 70°C followed by hot air drying at 70°C) reduced the total drying time by 25.93% to lower the pistachios moisture content from 38.14% (w.b.) to 8.90% compared with hot air drying at 70°C alone. Drying of pistachios in the SIRHA dryer using IR heating at 70°C for 20 min, 1 h, and 2 h and holding the pistachios at 70°C for 1 h followed by hot air drying to 8.90% MC resulted in Pediococcus population size reductions of 5.41, 5.60 and 6.39 log CFU/g, respectively, for pistachio kernels and 5.45, 5.42 and 5.29 log CFU/g, respectively, for pistachio shells. No significant difference in peroxide value and free fatty acid contents was observed for the pistachios dried with SIRHA method and hot air drying (70°C).
Significance: The results of this study confirmed the effectiveness of the SIRHA drying technology to achieve simultaneous drying and decontamination of pistachios.