Effect of relative humidity on drying characteristics of microwave assisted hot air drying and qualities of dried finger citron slices

Abstract The influence of relative humidity of hot air on the finger citron slices drying characteristics, properties and aroma during microwave drying process was investigated. A new microwave drying system with relative humidity control was developed. Three levels of relative humidity of hot air, 20%, 40%, 60% of material with the temperature of 70 oC were set in the experiments, with comparation under temperature of 70 oC without fixed relative humidity for hot air. Results showed that Page and Midilli et models were selected to predict the drying behavior within the experimental range with the highest R 2 . Samples dried under relative humidity 20% of hot air had the shortest drying time, highest rehydration ratio and porous structure. Samples dried under relative humidity 40% of hot air had the best color and aroma. Relative humidity 40%, 60% of hot air could provide better product quality than drying without relative humidity, followed by 20% and 60 % of hot air. The relative humidity 40% of hot air should be a compromise proposal.