摘要

P>Bitter gourd (Momordica charantia), a commonly consumed vegetable in South Asia, eastern-South Asia, China, Japan, Korea peninsula, Caribbean Sea isles etc., is used as an adjunct in the management of diabetes mellitus. In this study, in order to find the effective ways of producing bitter gourd freeze-dried powder, the concentrated juice of bitter gourd was produced through enzymatic process (EP), ultra filtration (UF), reverse osmosis and vacuum concentration technology. Results indicated that total saponins, total sugar and pH value in bitter gourd juice were almost unchanged after EP and after UF (P >= 0.05). However, UF decreased the turbidity and improved transmittance of juice (P < 0.05). When compared with the vacuum concentration alone, the combined process of reverse osmosis followed by vacuum concentration had 3.33 folds of production efficiency and 1.725 times of vitamin C content in concentrated juice. With freeze-drying microscope system, the eutectic point of the freeze-dried product of bitter gourd juice was detected to be -37.5 degrees C, which was important to optimise lyophilisation parameters. The freeze-drying microscope system was more accurate than the conventional electric resistance method in detecting the eutectic point of freeze-dried product.