Study On Superheated Steam And Vacuum Drying Technology Of Bamboo Shoots

Superheated Steam Drying Technology is a new type of food processing technology in recent years,the new technology has the advantages of short drying time,fast and energy saving.But owing to the restriction of its high temperature and incomplete equipment,the application and popularization are restricted.Vacuum drying can maintain the quality of material well but consume more energy.Bamboo shoots are highly seasonal and easily lignified,in addition,its quantity in China is large and bamboo shoots are unavailable for direct fresh.Thus,drying is the most convenient storage method.Traditional drying methods have the disadvantages of time consuming,poor quality and weather sensitive.Hot-air drying is energy-hungry with poor quality.Therefore,it is necessary to find a new drying method to dry foods quickly and keep good quality.Through the experimental study,it effectively combines the advantages of super heated steam drying and vacuum drying.In single experiment of superheated steam drying,using shrinkage ratio,rehydration rate and color of the bamboo shoots as indicators to study the influence of steam temperature and slice thickness of bamboo shoots on the quality of bamboo shoots during the drying process under superheated steam.The results indicated that the best shrinkage ratio and rehydration rate of the bamboo shoots could be achieved at 120?,and at this temperature,the color was best.When the slice thickness of bamboo shoots was about 4mm,the color of bamboo shoots was best,at the same time,the shrinkage ratio and rehydration rate of the bamboo shoots were much better.While on the whole,the color was tend to be duller than the raw materials,and the shrinkage ratio and rehydration rate of the bamboo shoots were not so good.In single experiment study of vacuum drying,using shrinkage ratio,rehydration rate and color of the bamboo shoots as the indexes to study the influence of temperature,slice thickness of bamboo shoots and vacuum degree on the quality of bamboo shoots during the drying vacuum drying.It turned out that the vacuum temperature should not be too high.The color kept well and the best shrinkage ratio and rehydration rate of the bamboo shoots can be achieved at 75?.The drying was fast and the color kept well when the slice thickness of bamboo shoots was no more than 4mm,what's more,the shrinkage ratio and rehydration rate of the bamboo shoots were much better in this condition.The vacuum degree should be neither too big nor too small,the reasonable one being 0.055MPa-0.075Mpa.On the base of single superheated steam drying experiment and single vacuum drying experiment,identifying three main influencing factors for the combination of super heated steam drying technology and vacuum drying technology were the superheated steam temperature,conversion time and vacuum temperature.Using the rehydration rate and color parameters L of bamboo shoots as indicators to analyse the study on the combination of super heated steam drying technology and vacuum drying technology and ascertain the standard regression model of the combination of super heated steam drying technology and vacuum drying technology which used the rehydration rate of bamboo shoots as index was:Y1=6.20-0.43X1-0.36X2-0.058X3+0.18X1X3+0.065X2X3-0.62X12-0.68X22-0.54X32.The standard regression model of the combination of super heated steam drying technology and vacuum drying technology which used the color parameters L of bamboo shoots as index is:Y2=90.52-7.34X1-8.46X2-2.25X3-5.50X-X2+2.46X2X3-10.05X12-8.07X22-12.97X32.Rehydration rate and color parameters L which were the indexes in the experiment were equally important.By the application of Design Expert8.0.6 software,the optimum parameters were as follows:the superheated steam temperature was 119.10?,conversion time was 34.71min,vacuum temperature was 73.66?,under this condition,the rehydration rate of bamboo shoots was 6.2488 and color parameters L was 93.2323.Verifying the optimum process condition and the results indicated that the experimental results showed good agreement with the predicted data.By the study on the superheated steam equipment and vacuum drying equipment,superheated steam combined with vacuum drying machine was produced.Superheated steam combined with vacuum drying and hot air drying process was used to dry bamboo shoots for its economic analysis.By comparing the data,it turned out that the drying time and the energy required to turn 1kg water to evaporation of superheated steam combined with vacuum drying was half less than the hot air drying.Then,the purpose of saving energy and time was achieved.