Explosion Puffing Drying And Isothermal Adsorption Characteristics Of Winter Jujube And Apple Slices At Variable Temperatures And Pressure Differences

The explosion puffing drying at variable temperatures and pressure differences is a newtechnique; it combines the advantages of hot-air drying and vacuum freeze drying. Whenmaterials gets to the temperature by steam heating, the pressure of tank is reduced tonegative immediately. The moisture was turned into vapor that makes up pressure duringhigh temperature application. The puffed-drying fruits and vegetables are free of additives,healthy and nutritious with excellent qualities. The research of puffing drying mainlyconcentrates to the crafts at home and abroad, such as preparation and technologicalparameters. It is at the initial stage of the study on the explosion puffing dryingcharacteristics.Explosion puffing drying was carried out on fresh winter jujubes and apples. Research theexplosion puffing drying characteristics and storing property, using physical analysis,chemical analysis and mathematics statistical analysis. It included effects of pretreatmenton the quality of winter jujube and apples, the change of apple polyphenol and vitamine Cduring the puffing drying, drying dynamics and storing property. Established the theorybasis and control production for the explosion puffing drying at variable temperatures andpressure differences.Compared effects of pretreatment on the quality of winter jujube and apple slices atmodified temperature and pressure. Anglicized the physical targets of winter jujubes andapple slices. The physical targets included hardness, color, porosity and dehydration. Themoisture content winter jujube was removed by hot air drying in56%,67%,79%. Thenexplosion puffing drying was carried out until the moisture content of winter jujubereached8%. The result was that the quality of winter jujubes under56%moisture contentwas best. The jujube slices had smallest hardness value, best rehydrate and porosity.Compared the different moisture content of apple slices, the quality of apple slices under30%moisture content was best.And took the effects of colour protection treatment andpuffing drying process on the quality of apple slices. Results showed that explosionpuffing drying technology had the stronger capacity of desulfur. Apple slices were preparedaccording to the process condition that color protection for apple chips were treated by0.02%sulfite and puffing drying process III. At these conditions, sulfur residues content ofapple slices could met the national standard2760-2007, and the apple slices were of goodcolour and crispness. During the drying stage, the content of polyphenol and vitamine C lost. Compared to the hot-air drying apple slices, puffed drying apple slices had morepolyphenol and vitamine C.The SPSS13.0software was used to analyze data. Selected thin-layer drying models,estimation package （SPSS13.0） was used to estimate drying stages. Results showed thatthe drying process of explosion puffing drying at variable temperature and pressuredifference obviously existed increase-rate, constant-rate and falling-rate period. Most ofdrying process was in falling-rate period. Henderson and Pabis model provided bettersimulation of drying curves for crispy winter jujube. Page model provided bettersimulation of drying curves for apple slices. The effective moisture diffusivity of appleslices dried by explosion puffing drying at variable temperatures and pressure differenceswas among1.52×10^-9～8.87×10^-9m²/s.The isothermal adsorption characteristics of puffed drying winter jujubes and apple sliceswas also studied. Effects of storage temperature and relative humidity on puffed dryingwinter jujubes and apple slices were researched. We could know that the isothermaladsorption curves of apple slices were counter-S obviously. When the relative humiditywas more than58%, the moisture content of apple slices increased along with temperaturesraised. Comparison isothermal adsorption curves of winter jujubes to apple slices, thecurves of jujubes were not counter-S obviously.The study on the explosion puffing drying characteristics has guidance significance forproduction, will provide academic and technical basis. It provides a reference for storageconditions and packing material on storing property of explosion puffing drying for fruitsand vegetables.