Simulation And Analysis Of Microwave Puffing Blueberry Snacks

Blueberry has a unique flavor,soft texture,and riches in nutrients which are beneficial to health.The fresh blueberry is difficult to be stored and transported.Therefore,blueberry products are common on the market,while the types are relatively simple.The blueberry snacks puffed by microwave are novel food with crispness and no-fried.The more nutrients within snacks are retained with high health.The vapor pressure inside the snacks generated by microwave is the driving force to cause the puffing of blueberry slices.Vapor pressure and elastic modulus have direct effect on the quality of the internal pore structure and expansion effect.At present,there was a lack of research in this area.Therefore,this study was carried out from the perspective of the driving force of puffing process and analyzed the process of puffing snacks.In order to analyze the variation of vapor pressure,elastic modulus other parameters during the microwave puffing blueberry snack process,the changes of temperature,pressure,water vapor volume,elastic modulus and volume were determined by single factor test.The simulation software was applied to describe the puffing process and analyze the berry snacks puffed process.The model for the variation of pressure and temperature in the snacks during the process of microwave expansion was established.The effect of pressure on the volume change of the snacks and the conditions of the porous structure were analyzed.The results were as follows:(1)The increase rates of pressure,temperature,the amount of water vapor and volume were proportional to the microwave power,and the maximum value was inversely proportional to the snack weight.The greater the microwave power resulted in the smaller the initial moisture content,and the higher the elastic modulus of blueberry snack.The larger the initial moisture content resulted in the higher the internal pressure of the snacks in the early stage of puffing,the more expansion force in the later stage.The maximum volume of the snacks occurred when the initial moisture content achieved 23%.The puffing time had no significant effect on the puffing phenomenon.(2)Four processes in terms of energy absorption,heat accumulation,water evaporation,and volume expansion presented in the berry snacks puffing process.In the early stage of microwave expansion,the absorption of microwave energy within blueberry snacks generated thermal amount.Heat accumulation increased the temperature of the snacks and the water evaporation.The evaporation of water formed a porous structure inside the berry snacks.The generation of water vapor increased the internal pressure in the snacks,reduced elastic modulus,and made the volume expansion of berry snacks.The water diffused to the surface under interaction driving force between gradients of temperature and pressure.In the late stage of microwave puffing process,the moisture content of the berry snacks decreased.The decrease of absorption of microwave energy resulted in the reduction of temperature rising rate and moisture diffusion rate.The internal porous structure and volume of the fruit slice were stable,and the microwave expansion process was completed.(3)The changes of pressure and temperature inside berry slabs with time in the puffing process were analyzed to build regression equations.The volume expansion of berry snack could be calculated based on this regression equation as the function of temperature and pressure.A similar theoretical model between puffing conditions and objective indexes was established to provide technical basis to control the expansion extent of microwave puffed berry snacks.The puffing law and model of microwave expanded blueberry snacks could provide a theoretical basis for the puffing blueberry snacks in industrial scale.