Modeling of Roasting Process of Peanut Kernels using Combined Infrared-Hot Air Method

Roasting is one of the common methods of nuts processing and its purpose is to increase the total acceptability of products. The conventional roasting using hot air oven has drawbacks of low production rate, poor product quality, and high energy cost. Therefore, there is a need to develop new processing methods that can produce roasted products. The combined infrared-hot air system was explored as a new roasting method for peanut kernels.

In this study the combination of infrared (IR) and hot-air was explored for roasting of peanut kernels and the effects of processing conditions including hot air temperature (100 and 120 °C) and infrared power (130 W, 165 W and 200 W) on different characteristics of kernels (moisture content and energy consumption) were investigated. Roasting kinetics of peanut kernels were explained and compared using five mathematical models. In order to determine the coefficients of these models, non-linear regression analysis was applied.

According to the statistical analysis, two-term and logarithmic models showed the best fitted results. These models have acceptable R2 and adj R2 and low RMSE under all roasting conditions. Effective diffusivity coefficient of peanut kernels varied between 1. 915× 10-7 - 6.054× 10-7 m2/s. The value of Deff increased by increasing temperature and IR power. The results also showed that by increasing temperature and IR power, the moisture content (%, db.) of samples decreased and energy consumption increased.

This study demonstrated that combination of infrared and hot-air roasting can produce high-quality roasted peanuts with lower energy cost; therefore it could be considered as a new technology for the peanut roasting industry.