Anaerobic Heat Pump Drying Equipment Research And Development And Carrot Drying Dynamics Research

At present,The main rearch direction of drying technology is to improve thequality in fruits and vegetables during drying process.The quality deterioration offruits and vegetables is enzymic catalytic reaction inside inside.The temperature andoxygen in environment can effect the quality too. The only way to improve the qualityof fruits and vegetables is to isolated from oxygen,passivation oxidase, and reduce thedrying temperature.We usually use the method by adding antioxidants （Na₂SO₃） andheating （95℃3min-5min） to passivate enzyme during production.But there aresome problems such as the lossing of water-soluble nutrient,energy consumption andthe residues of Na₂SO₃. Vacuum drying and vacuum freeze drying are the mainmethods to reduce the oxygen level and temperature.But they cost too much,so thehot-air drying is still using widely because of its high efficiency and low cost.We haveto explore a new method for fruits and vegetables which are sensitivity with oxygenand temperature.This drying method is one of the key point at agricultural productsdrying field in domestic.The basic idea of anaerobic heat pump drying is closed-type hot-air drying bythe using of inert gas （N₂or CO₂） instead of conventional air and dehumidification bythe heat pump system.This drying method can improve drying rate,and the driedproducts is porosity,quick rehydration,and good color compared with hot air dryingmethod.We rearched and developed anaerobic heat pump drying equipment by thetransformation and optimization of heat pump equipment.The equipment is2000mm inlength,1500mm in width and2000mm in high.There is a sufficient room for drying100kg material.We added auxiliary fan, auxiliary heater, temperature sensor, humiditysensor, and detecting material internal temperature sensor in it.The box was sealed by sealant.The equipment is not only sealing performance good but aslo realizinganaerobic environment under normal pressure drying.In this paper,we compared hot air drying,Vacuum drying and vacuum freezedrying,detected the changes in moisture content and drawed the rate curve duringdrying.We detected the color, negative water rate, degree of deformation, and β-carotene content in carrots.And we studied the internal heat transfer mechanism incarrots during anaerobic pump test equipment drying process for building dryingmodel.The results shows that β-carotene retention is high when the drying temperatureis at50and60℃during hot air drying,but the overall drying effect is not good.The β-carotene retention is better than hot air drying during Vacuum drying andtimesaving.Anaerobic heat pump drying is the most energy saving method,and thedrying effect is better than vacuum drying but time-wasting.