摘要: An innovative two-stage drying concept is presented in this article,based on quality degradation depending on temperature and water activity.This work considered drying of carrot slices using a combined drying in a pilot deep bed ... 展开 An innovative two-stage drying concept is presented in this article,based on quality degradation depending on temperature and water activity.This work considered drying of carrot slices using a combined drying in a pilot deep bed dryer,the first stage heat pump drying at low temperature and the second stage hot-air drying in short time,to improve the product quality and reduce drying time.The results showed high quality products were achieved using the combined drying and the conjunction where heat pump drying with low temperature switched to hot air drying could affect the general drying performance and product quality.The optimal combined drying process was determined based on the degradation of β-carotene,rehydration ratio,color and the free water content analyzed with magnetic resonance imaging (MRI),which was that at the beginning,the carrot slices were dehydrated to about 40％ w.b.undergoing heat pump drying at 40℃,then dried to 10％ w.b.using temperature-programmed hot-air drying at 70℃.The firststage heat pump drying could remove 95.44％ of free water in carrot slices with the specific moisture extraction rate (SMER) over 0.7 kg water/kw·h.A comparison of the color of products showed that the combined drying reduced the colour change less than the heat pump drying.The retention of β-carotene and rehydration ratio were very close to those dried by heat pump drying,higher about 59％ than hot air drying and higher about 52％,separately.The drying time of the combined drying was reduced about 28.6％ compared with the 10.5 hours of heat pump drying. 收起