The freshness-keeping effect will be better when fruits and vegetables are treated by natural Chinese herbal extracts. The major methods applied with the extracted substances are dipping, fumigating, spraying, as preservative paper and coating agents.
Dipping in the Chinese herbal extracts
Early studies mainly focused on how the ordinary aqueous extracts of natural plants act to preserve fruits and vegetables after they are dipped. Wu et al. used wintergreen extracts with 3 different concentrations to dip apples with brown rot under room temperature. It came out that these 3 extracts suppress and delay more or less the further infection of brown rot towards the apples, the higher concentration the better effects. Duan et al. chose the extracts of honeysuckle, Rheum officinale and galangal as three Chinese herbal medicines to preserve cucumbers. The final data indicated that the cucumbers dipped with these 3 herbal extracts are much better than the control in terms of appearance, survival rate of vitamin C and water-holding capacity. In particular, cucumbers treated with the combination of honeysuckle and galangal behave the best because they are less in weight loss, change of vitamin C, longer in time of preservation and better in keeping their colors. These results suggested the potent ability of herbal extracts in keeping vegetables fresh. Immersing the post-harvest strawberries in a mannosan solution containing 0.05% konjak for 1 week made the fruit lose a little surface gloss but not go moldy even after 3 weeks. However, strawberries free of the treatment lost the gloss after 2-day preservation under room temperature and went moldy after 3 days.
Applying the Chinese herbal extracts
When Chinese herbal medicines like Radix stemonae, Polygonum cuspidatum, galangal and berberine are subject to supercritical extraction and the resultant extracts are blended with starch, konjak and lecithin, these can be made into complex semipermeable membrane of herbal…