Effect of physical parameters on uniformity of temperature profile of Pistachio (Fandoghi cv.) during microwave heating

Heating is one of the most commonly used methods for accessing various purposes in the food process. The main problems with microwave heating are the possibility of cold and hot spots. The aim of this study was to investigate the uniformity of temperature distribution in Fandoghi Pistachio under the microwave heating process under study conditions. Independent factors included the shape of product geometry, the position of the thermometer and the heating time. This research was based on a completely randomized design based on a factorial experiment of 2×6×4. Independent factors included the shape of product geometry, the position of the thermometer and the heating time. These experiments were performed separately for 900 and 630 w microwave power, and the temperature of the pistachio product was measured and recorded during the four-time heat treatment at six different positions of the product as an associated factor. The results of this study were based on two types of analysis of the comparison of the mean temperature of the samples and the determination of the relative non-uniformity index. The results showed that all the main effects were significant at 1% level in both applied power states. Comparison of means showed that in treatment "B" (cubic - 630 w) in 5 positions of 6 positions, there is no significant difference between the mean temperature under investigation. This means that the temperature distribution at different product positions at the end of the microwave heating period has been quite uniform. Subsequently, the cubic – 900 w and cylindrical- 630 w had the highest uniformity in temperature distribution. By calculating the relative non-uniformity index, the highest uniformity was obtained in cubic - 630 w.