Effect of some chemical solutions during pretreatment and different freeze drying conditions on quality of mango = ผลของสารละลายระหว่างการแปรรูปขั้นต้นและสภาวะการอบแห้งแบบระเหิดที่แตกต่างกันต่อคุณภาพของมะม่วง


พีระพร แก้วพูลผล


วิทยานิพนธ์. (2017) 88 หน้า



Nam Dok Mail mango is among the major export products of Thailand. Many mangoes, however, do not pass the enterprise stringent preliminary quality check because of their visible defects. These mangoes should then be transformed into a value-added dried product by using an appropriate technology, including freeze drying. The aim of this study was to investigate the effect of different anti-browning compound concentrations during pretreatment on the quality of freeze dried mango. Suitable freeze drying condition was also determined. Mangoes were cut into chunks and dipped in combined ascorbic acid and citric acid at 3 concentrations (0, 1 and 2% w/v). Then, freeze drying was performed at secondary drying temperatures of 30 °C and 40 °C. During the sublimation step, the maimum temperature was limited by the thermal transition behavior of mango. The maximum ice formation temperature (T'm) of mango was determined by DSC to -37 °C. Upon drying the moisture content and water activity of the freeze dried mango were in acceptable limits for safe storage, in the ranges of 2.34 to 2.73% wet basis and 0.20 to 0.26, respectively. No significant differences (p>0.05) in the moisture content were noted aming the samples undergone drying at different temperatures and pretreated in different ways. However, increasing the secondary drying temperature resulted in a decrease in the water activity. The L* and b* values of the freeze dried mango were significantly different (p≤0.05) from those of the fresh mango upon increased drying temperature and when pretreatment was applied. ΔE values were in the range of 14.00 to 21.51. Significant differences (p≤0.05) were found in the ΔE among the samples dried at different secondary drying temperatures. However, secondary drying temperature did not significantly (p>0.05) affect the hardness of freeze dried mango. It was concluded that the anti-browning compound concentration during pretreatment did not affect the overall quality of the freeze dried mango The suitable freeze drying condition wa freezing at -30 °C prior to afjustment of the primary drying temperature slowly from -30 °C to 0 °C and then using a secondary drying temperature of 30 °C