Experimental Study On Microwave Assisted Dehydration And Puffing Process Of Blackcurrant Fruit

Blackcurrant is rich in active ingredients such as anthocyanins,which has high nutritional value and health benefits.However,due to its high moisture content,it is difficulty to be stored.Fresh blackcurrant berry is too acidic to eat,so it is often used in deep processing.Microwave-assisted osmotic dehydration and intermittent puffing technology not only have the advantages of volumetric heating and high drying rate,but also may retain nutrients in fruits to the maximum extent by osmotic dehydration and intermittent puffing technology,which may effectively shorten the processing time and improve the quality of blackcurrent fruit.The objective of this study is to investigate the microwave-assisted osmotic dehydration and intermittent puffing process of whole blackcurrant fruit.Firstly,response surface methodology was employed to analyze the osmotic dehydration characteristics of blackcurrant fruit,and a mathematical model was established between the experimental factors and the initial moisture content of blackcurrant fruit,which optimized process parameters of osmotic dehydration.The changes of moisture content,temperature,expansion ratio and other parameters were explored by the single factor experiment of microwave puffing,and the microwave puffing heat and mass transfer model were established by COMSOL software.Considering the simulation results,the heat and mass transfer mechanism in the microwave puffing process of blackcurrant fruit were analyzed.Finally,response surface methodology was used to analyze the quality of the puffing products,and the parameters of optimum blackcurrant puffing process were determined.The research conclusions are as follows:(1)It was found that the water loss and solid gain increased with the increase of Brix degrees,osmotic time,number of microwave action in the microwave-assisted osmotic dehydration experiment of whole blackcurrant fruit,and the water loss and solid gain initial increased and then decreased with the increase of microwave power.The water diffusivity and solid diffusivity decreased and then increased with the increase of microwave power,and these increased with the increase of Brix degrees and number of microwave action,while these decreased with the increase of osmotic time.(2)The results of single factor test of microwave puffing showed that the microwave puffing process of blackcurrant consisted of three stages in terms of acceleration,constant speed and deceleration stage.The temperature of blackcurrant fruit showed a fluctuating upward trend during intermittent microwave puffing.The final temperature of the fruit rose at high level of initial moisture content and microwave power.The volume change of blackcurrant could be divided intotwo stages: shrinkage stage and expansion stage during microwave puffing.The simulation results showed that the temperature and moisture in the whole blackcurrant fruit showed a tren d of high center and low surface during microwave puffing.Temperature and moisture of blackcurrant changed rapidly in the initial stage of microwave puffing,while the trend of temperature and moisture change slowed down in the later stage of microwave pu ffing.(3)The optimum intermittent microwave puffing process parameters to achieve the expansion ratio of 152%,hardness of 1593.5 g,brittleness of 1014.92 g.s,and comprehensive chroma Ec value of 8.91 from blackcurrant were obtained under the expansion ini tial moisture content of 50%,microwave power of 800 W,single microwave heating time of 1.5 min,and single microwave intermittent time of 3 min.Microwave-assisted osmotic dehydration and intermittent microwave puffing of whole blackcurrant fruits are proposed in this paper.The puffed blackcurrant fruits have moderate hardness and brittleness,similar appearance to the original fruits with fine sour and astringent tastes,which can provide technical basis for the processing of blackcurrant berries leisur e food.