The Far-infrared Drying Technology Research Of Red Jujube Sheet

Red jujube is rich in nutritional value and have certain health care and medicinal value. The Xinjiang red jujube is loved by most consumers as a quality characteristics fruit of China. The red jujube planting area of Xinjiang accounts for 17.12% of the nation. Most of the red jujube is still in the natural drying method to complete the whole jujube drying process. The drying time of troditional methods is long and the quality of the dried products is uneven, the product is single and price is low. It’s lack of the market competitiveness. This article adopts a new type of heating technology which be used for the drying of jujube slice with jujube puree based on far-infrared radiation. It will be studied of the red jujube slice far-infrared radiation drying kinetics under different radiation temperature, thickness and radiation distance.Make a reasearch of the dried jujube sensory quality and VC content influence under different drying conditions and optimize to obtain the best drying conditions through the response surface method of the impact factors.In order to studying the far-infrared radiation drying kinetics of red jujube slice and the effect of different drying conditions on VC content and sensory quality. Firstly, single factor experiments were carried out at different radiation temperatures（55⁷5 ℃）, different thickness（2⁶ mm） and different radiation distance（80¹40 mm）. Get the results as the follows:In the range of test conditions, the Jujube slices drying belong to slow down drying during the whole drying process and the water effective diffusion coefficient is during 1.10674×10^{-10 9}.67179×10^-10 m²/s.The effective diffusion coefficient of water increased with temperature rising and the drying energy of activation needed is 53.79 kJ/mol. The radiation temperature, slice thickness and radiation distance all have significant influence on drying time through the variance analysis. The significant sequence is: the radiation distance is higher than slice thickness and the slice thickness is higher than the radiation temperature.We found that the radiation temperature, slice thickness and radiation distance had significant effects on VC content of red jujube after measuring and analyzing the VC content of the dried jujube. VC content obeys the following order: radiation temperature, radiation distance, slice thickness. Radiation temperature is too low or radiation distance is too large, both of which lead the drying time longer and VC lose more.The radiation temperature is too high will make the material surface browning seriously. It is recommended that no more than 70 ℃ and thickness should be 4 mm.Make a analysis of the sensory quality of the dried jujube slices found that different radiation temperature and slice thickness all have significant effects on jujube piece of sensory quality. Radiation distance have no significant influence on the sensory quality of dates. The radiation temperature higher will leads the date slightly anxious burnt surface and tastes bitter also it can affects the color and flavor then the date would have a poor quality. The lower the temperature is, the longer the drying time is. It can lead to bitter taste and poorer sensory quality. We suggest that the temperature is between 60⁷0 ℃. The thinner thick leads to the drying time shorter and sensory quality poor.The impact factors of red jujube piece of far infrared radiation drying for response surface designed and optimized using the Design Export 8.0.6 software. Build a model for drying time, sensory quality and the content of VC through the response surface method on red jujube piece drying. We known that the regression model is significant and the regression equation was fitted well with the experimental results.Through the result of the three factors influence on jujube response surface analysis can predict the best drying process conditions: radiation temperature 63 ℃, 4.3 mm thick, radiation distance is 115 mm. The optimization results are considered acceptable after experimental verification.