不同干燥方式对核桃青皮品质的影响

采用晒干、阴干、热风干燥、微波干燥和中短波红外干燥对核桃青皮进行干燥处理,研究不同干燥方式对核桃青皮含水率、色差、总酚、总黄酮和蒽醌类物质含量及干燥时间的影响。结果表明:干燥至恒重时,微波干燥所用时间最短,为0.4 h,干燥速率显著高于其他干燥方式(p<0.05);中短波红外干燥次之,时间为8 h。晒干所得的青皮中总酚、总黄酮和蒽醌类物质含量最高,分别为46.98、13.79和5.37 mg/g,显著高于其它干燥方式(p<0.05);中短波红外干燥得到的核桃青皮中总酚、总黄酮、蒽醌类含量分别为43.13、12.23和4.36 mg/g。50℃热风干燥后的核桃青皮粉末色泽最浅,ΔE~*值为65.05;中短波红外干燥次之,ΔE~*值为67.98。综合比较五种干燥方式,晒干得到的产品品质最好,但受天气影响较大;阴雨天气下,50℃热风与中短波红外干燥后的核桃青皮品质没有明显差距,但中短波红外干燥时间仅为50℃热风的1/3,效率更高,更适合核桃青皮的干燥。 

Effects of different drying methods on the quality of walnut green husks

The effects of different drying methods ( drying in the shade, sun drying, hot air drying, microwave drying and medium-short infrared wave drying) on the drying properties ( moisture content, color difference ( ΔE^*) , total phenols, total flavonoids, anthraquinones and drying time) of walnut green husks ( WGH) were studied.Results showed that it took the shortest time of 0.4 h to get constant weight by microwave drying, indicating the fastest drying rate, followed by medium-short infrared wave drying ( about 8 h) .In addition, contents of total phenols, total flavonoids and anthraquinones in the WGH dried by sun were 46.98, 13.79 and 5.37 mg/g, respectively, which were significantly higher than other drying methods ( p < 0.05) . Contents of total phenols, total flavonoids and anthraquinones in the WGH dried by medium-short infrared wave drying were 43.13, 12.23 and4.36 mg/g, respectively.The color of WGH powder by hot air drying at 50 ℃ was the lightest and the value of ΔE^*was 65.05, followed by medium-short infrared wave drying with ΔE^*of 67.98.By comprehensive comparison of the five drying methods, the quality of the WGH dried by sun was the best, but affected by the weather easily. In the rainy weather, there was no significantly difference between 50 ℃ hot air drying and medium-short infrared wave drying.Moreover, the time by mediumshort infrared wave drying was only 1/3 of the time by 50 ℃ hot air drying, therefore, taking drying efficiency into consideration, the medium-short infrared wave drying was more suitable for WGH drying.