Study On The Combination Of Vacuum Impregnation And High Temperature Heat Pump Drying On Mango

The processing conditions of dried mango were investigated systematically to reduce drying time, improve mass transfer and produce high quality product. With combination of Vacuum Osmotic Dehydration(VOD) and Hot Pump Drying affect on the quality of mango varieties, a cultivar suitable for processing into dried form was optimized. A new approach for pre-dehydrate mango was obtained by adopt different pretreatments-Vacuum Osmotic Dehydration to enhance mass transfer efficiency and to shorten immersion time. Furthermore, application of high temperature heat pump intermittent drying overcoming the disadvantages of internal moisture evaporated imbalance of and surface hardening. The main results or conclusions were as follows:(1)fresh and VOD-Hot Pump Drying samples(VOD-HPD) of six mango cultivars presented significant differences in physicochemical and sensorial characteristics, including total sugar, total acid, the ratio of sugar to acid, V, color and texture. Narcissus mango was played an excellent role in processing into dried mango with appropriate sugar, total acid, VC, firmness and brighter color. The characteristics of Tainong No.1 and JinHwang were also properly processing.(2)VOD effectively enhanced the WL and SG during the OD process. Firmness, protopectin content and water soluble pectin content of mango tubes decreased, decreased and increased, respectively. Changes of microstructure of mango cubes indicated that the cell volume and intercellular space increased immediately after released to atmospheric pressure, then gradually recovered. The majority of the variation in WL, firmness, protopectin content, water soluble pectin content and microstructure of mango cubes were observed within the first 60 min. In addition, results of correlation analysis revealed that firmness of mango cubes was positively correlated with the protopectin content(p>0.01), but negatively correlated with WL and the water soluble pectin contents(p>0.01), indicating that WL and degradation of protopectin contributed greatly to the loss of firmness.(3)This study indicated that three pretreatments had a positive influence on the WL and sugars of VOD treated mango cubes. The highest WL and sugar gain was vacuum microwave 4 min, frozen respectively. The effects caused by different pretreatments(frozen, ultrasound and vacuum microwave) on totalacid, color, texture were negative. Mango with frozen pretreatment had the highest sugar and much smaller color change compared with fresh sample. Thus, frozen was chosen to combine with VOD as the new unit of pre-dehydration process.(4)The results of high temperature heat pump treated mango showed that the higher the temperature, the lower the moisture ratio and the faster the drying rate; the longer the intermittent time, the lower the moisture ratio and the faster the drying rate; the moisture ration and the drying rate of intermittent drying declined more rapidly, more quickly than that of continuous drying and shortened drying time. Midilli model was well fitted the drying curves. The optimal process was obtained at 55℃intermittent for 4 h. Under this condition, dried mango preserved better brightness, more yellow and lower total acid. Besides, the damage of β-carotene was least.