Study On The Technology Of Explosion Puffing Drying By Variable Temperature And Pressure For The Sweet Potato Chips

In the study, with fresh sweet potato as raw materials, were puffed in the fruit and vegetable variable temperature different pressure puffed drying equipment to study the influence of the puffed sweet potato chips by different pretreatment conditions,screen the key factors of influencing expansion puffing process, and optimize the puffing process. The changes of sweet potato nutrient compositions and the micro structures were also discussed. The effect of three drying methods on the physic-chemical properties, the nutrient compositions and the micro structures of the products were compared. The quality standards of products were established. This study provides theoretical support for the subsequent research of expansion puffing technology, and have certain reference value for expanding expansion puffing technology of our country.Through the investigation and comparative analysis on the optimal process, the physic-chemical properties, the nutrient compositions and the micro structures of the products of of sweet potato products dried by explosion puffing and other different drying methods, the conclusions can be summarized as follows:(1)The optimal pretreatment conditions:heating pastingtime was5min, frozen temperature was-20℃, frozen time was15h,dehydration solution was15%maltose syrup solution, dehydration time was8h. The key factors was determined through single factor experiment:thickness was2mm, expansion puffing temperature was90℃, vacuum temperature was90℃, vacuum time was1h, pressure difference was0.3MPa, dwell time was20min. A central composite rotatable design (CCRD), frequency analysis and interactive factor analysis method was adopted to optimize the technology of explosion puffing drying for sweet potato, the optimum process parameter scope is:expansion puffing temperature was89.25℃～95.22℃, vacuum drying temperature was85.89℃-90.01℃, vacuum drying time was0.92h～1.20℃.(2)The nutritional components changes of sweet potato under expansion puffing process:vitamin C, beta-carotene, crude starch content of the products are reducd to compare to fresh samples; reducing sugar content was increased; crude fiber, crude fat, crude protein content in the pretreatment process was declinedand and was rebounded by puffed. Through the scanning electron microscope (sem), explosion puffing process made the internal cavity expanded obviously, tissue was distributed more uniform, and the structures were similar to the sponge structure, and the products was crisp delicious on the palate.(3)Comparative investigation were conducted on the chemical and physical properties, nutritional components and micro structures by three different methods (explosion puffing drying at variable temperature and pressure difference, vacuum freeze drying and hot air drying), The results indicated that: the hot air drying led to poorer physical properties, organoleptic quality and nutritional components, close structure and hard palate; vacuum freeze-drying made products got lighter color, reduced nutritional components less, but lower hardness; explosion puffing drying method made the products got good quality which was hardness modest, better color and lower water content, higher rehydration rate.