不同干燥方式对核桃仁及核桃油理化品质的影响

Effects of drying methods on physical and chemical quality of walnut kernel and walnut oil

考察了热风、红外辐射和微波辐射3种干燥方式对核桃仁及压榨核桃油理化品质的影响。通过测定核桃仁含水率、含油率以及压榨核桃油含水率、酸价、过氧化值、色值和氧化稳定性指标考察了核桃仁及核桃油在干燥过程中理化指标的变化规律。结果表明:经过不同温度加热核桃仁含水率随加热时间延长呈现下降趋势,且随加热温度升高,下降速度増快,3种干燥方式的失水效率为微波辐射>红外辐射>热风;经过不同干燥方式加热后,核桃仁的含油率下降由多到少的顺序为微波辐射>红外辐射>热风; 3种干燥方式中微波辐射处理对核桃油含水率影响不明显;加热后,压榨核桃油的酸价和过氧化值均呈现短时间内降低,然后升高的规律;经过3种干燥方式处理后,核桃油的颜色都发生了变化,且随加热时间的延长差异越来越显著;干燥初期核桃油的氧化稳定性均得到提高,其中热风、红外辐射和微波辐射时氧化稳定性最高分别升高到4. 39 h(120℃加热90 min)、5. 39 h(150℃加热90 min)和5. 0 h(中火,15 min)。

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 to4.39 h(120℃for 90 min),5.39 h(150℃for90 min)and 5.0 h(moderate fire for 15 min),respectively.