Study On The Process Of Explosion Puffing Drying For The Yam Chips And Its Quality

The drying technology at variable temperature and pressure difference is a new technology which has a development prospect, it can be effective for reserving the original nutrition and flavor of garden stuffs. In the paper, yam has been taken as the research object, the drying technology at variable temperature and pressure difference of yam had been optimized through the QDPH-V5 variable temperature differential drying equipment which recently exploited by the QinDe New Material Science and Technology Ltd., the impact of modes included hot air drying, microwave drying, vacuum freeze drying and differential pressure on physicochemical property of yam had been contrastive analysised. The main research results are as follows:(1) The change of puffing temperature, evacuated temperature and evacuated time could markedly affect the rehydration ratio, color and yield of yam chips. With the increasing of puffing temperature, the rehydration ratio, color and yield of yam chips would all first increase and then decrease. The rehydration ratio would decrease with the increasing of evacuated temperature, the color first rose after falling with the increasing of evacuated temperature, the percentage of contraction rose with the increasing of evacuated temperature; rehydration ratio and color of products would first increase and then decrease with the increasing of evacuated time, the percentage of contraction would rise with the evacuated time increased.(2) The regression equation of the comprehensive score for yam chips had been constructed:Y=6.97-0.63X1-1.61X2-1.07X3+0.38X1X2-0.14X1X3+0.044X2X3-0.67X12-0.57X22-0.92X32(R2=0.9396), we can see from the equation, which impacted yam chips mostly could be evacuated temperature(X1) and evacuated time(X2). The optimized technological parameter of drying technology at variable temperature and pressure difference could be puffing temperature of 87℃, evacuated temperature of 74℃, evacuated time of 138min, on this condition, the regression equation yam chips could be 1.82, L value of color would be 91.32, the shrinkage rate was 36.12%. The results of analysis of regression showed that:the determination coefficient of regression model was R2=0.9237, the model can be used in dried process condition control and dried prediction results.(3)Sensory index include color and rehydration ratio microwave drying product would be poorer, nutritional ingredients of products such as flavonoids, allantoin severe lost, the structure of the internal was compact, and the product had high hardness; the sensory index of products included color and rehydration rate for hot air drying all had a poorer performance, the product nutrients such as protein, flavonoids had heavy lost; vacuum freeze drying could save the color of products and the turnover rate of yellow ketone, allantoin and other nutrients was low, but the products could be fragile, and unsuitable for save and transport; the quality evaluation index included nutrient composition, shrink rate, and rehydration rate of the yam Slices dried at variable temperature and pressure difference were all acting well, so the products quality was good.