Novel hybridized infrared-hot air method for roasting of peanut kernels

Roasting is an important step in the processing of 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 degrees C), infrared power (130 W,165 W and 200 W) and roasting time (10, 20, 30 min) on different characteristics of kernels.(moisture content, color, textural characteristics, chemical properties, specific energy consumption and sensory properties) were investigated. The results showed that increasing the roasting air temperature, infrared power and roasting time decreased the moisture content, fracture force, hardness, apparent modulus of elasticity, compressive energy, pH and solid soluble content and increased the browning index, total phenolic compounds, and total acceptance of peanuts kernels. The total color difference (Delta E) varied from 2.87 to 19.33. After roasting, hardness of the peanut kernels reduced from initial 91.31 to 33.86 N and total phenolic compounds value were 2.71 mg GAE/g, all in the acceptable limit for good quality of roasted peanuts. The lowest value of specific energy consumed in roasting peanut kernels was observed at 100 degrees C and 200 W for 10 min (5.06 kWh/kg) and the highest value was at 120 degrees C and 130 W for 30 min (23.20 kWh/kg). This study demonstrated that combination of infrared and hot-air roasting can produce high-quality roasted peanuts with lower energy cost and time roasting; therefore it could be considered as a new technology for the peanut roasting industry. Industrial relevance: Infrared radiation could be considered as a promising technique for roasting of soybeans due to lower energy cost. (C) 2016 Elsevier Ltd. All rights reserved.