Hot air drying characteristics and process parameters optimization of jujube

In order to solve the problems of poor drying quality, low efficiency, dry and not prone to decay in jujube, the moisture loss characteristics of jujube were studied. Through designing the single factor drying test of jujube, the moisture loss characteristics of jujube under different drying temperatures, wind speeds and humidity conditions were studied, the variation of moisture content and drying rate were revealed. Using the response surface optimization method (Box-Benhnken), the response of different drying factors and interaction for drying quality moisture loss characteristics were studied, and the drying quality optimization fitting equation was established to obtain the best drying parameters. The results showed that temperature mainly affected the color of epidermis (around 55°C was the optimal), and humidity decided the shrinkage (about 60% was the optimal), while the wind speed had a significant effect on the smell of jujube (best results when the wind speed was about 0.35 m/s). The significant influence order of the test influence factors on the comprehensive quality score of jujube drying was: Drying temperature>humidity>wind speed; The verification of the parameters optimization was carried out: When the jujube drying, temperature was 55°C, humidity was 59.00%, the wind speed was 0.34 m/s, and the comprehensive quality score was 8.91. The relative error between the verification test value and the theoretical optimization value was 1.44% and less than 5%. This test can provide technical reference for the production of jujube drying process. © 2019, Asian Association for Agricultural Engineering. All rights reserved.