Abstract:

The effects of different drying methods on the contents of hypoglycemic components in balsam pear (Momordica
charantia L.) were explored to find the most appropriate one to retain the hypoglycemic components. Balsam pear
polypeptides were measured by the biuret method, polysaccharides by the phenol-sulfuric acid method, and saponins by
spectrophotometry. Meanwhile, the activities of alpha-glycosidase and alpha-amylase were assayed. The results showed that
freeze-dried balsam pear indicated the best color and lower losses of the main hypoglycemic components. By contrast, the
color of microwave-dried balsam pear was the worst, in addition to greater losses of the hypoglycemic components. Vacuum
drying was more time consuming, and caused higher losses of the hypoglycemic components and color deterioration in
balsam pear as compared with hot-air drying. The 8-h dried product by hot air drying had better quality and contained
(2.31 ± 0.11)% of saponins showing no significant difference compared with the freeze-dried one. Besides, the contents of
polysaccharides and polypeptides were (7.43 ± 0.04)% and (0.11 ± 0.06)%, respectively, which were significantly higher and
lower than those of the freeze-dried sample, respectively. At the same time, in vitro experiments indicated that hot-air dried
balsam pear powder had an obvious inhibitory effect on alpha-glycosidase and alpha-amylase. Therefore, hot air drying is
more appropriate for balsam pear.

Key words: balsam pear, drying, saponin, polysaccharide, polypeptide