| The effects of hot air, infrared radiation and microwave radiation on the physicochemical quality of walnut kernel and pressed walnut oil were investigated. Through determination of the water content and oil content in walnut kernel, the water content, acid value, peroxide value, color and oxidation stability of pressed walnut oil, the change law of physicochemical indexes of walnut kernel and walnut oil during drying were investigated. The results showed that the water content in walnut kernel at different temperatures decreased with heating time prolonging, and the decreasing speed increased with the increase of heating temperature. The order of the water loss efficiency of the three drying methods from high to low was microwave radiation, infrared radiation, hot air. The oil content in walnut kernel decreased from high to low was microwave radiation, infrared radiation, hot air. Microwave radiation treatment had no obvious effect on water content in walnut oil.The acid value and peroxide value of pressed walnut oil after heating decreased in short time, and then increased. After being heated by the three drying methods, the color of the walnut oils all changed, and the difference was more significant with the heating time prolonging. At the initial stage of drying, the oxidation stability of walnut oil improved, and the oxidation stabilities of walnut oils by hot air, infrared radiation and microwave radiation increased to 439 h (120?℃ for 90 min), 5.39 h (150?℃ for 90 min) and 50 h (moderate fire for 15 min), respectively. |
