| Amorphophallus Konjac is a herb of the Araceae Amorphophallus, which distributed mainly in some countries in the tropic and semitropical zone of the Asia and parts of the Africa, And it is very abundant in ous country. But a commonly encountered problem in the initial process of the Konjak when peeling off or sliceing up, is the brown stain. So this thesis performed a systemic research about the brown stain on it. Briefly, we took the Amorphophallus mairei (A.mairei) in wanyuan, and the A.white as the study material first, then we compared the changes of the polyphenol oxidases' activity and the total polyphenol in this two kinds of konjacs. Centred with the brown stain and the polyphenol's oxidadation, this paper has also carried out some other eperiments relevant them. The main contents and the results are as follows:1. We took the spectrophotometre to measure the activity of the polyphenol oxidase and the extent of the brown stain, and the method of Folin to measure the content of the polyphenol, and the results shown that the extent of the decreasing of the white konjac's is lower than the A.mairei, when preservatived in normal temperature after the postharvest. And the quantity of the total polyphenol in white konjak's corm is higher than the A.mairei's. The extent of the white konjac's brown stain is less than that of A.mairei's.2. When using the ultraviolet scan on the two konjac's brown stain of their substances, the wave peaks of them were at the same place with the dopamine. So the substances of their brown stain maybe a substance of the dopamines.3. Using the gel electrophoresis of the condense concentration 4.5% and the separate concentration 7.5% of the polyacrylamide, to apart the two kinds of konjacs. Then according the same zone when coloration the gel electrophoresis, we got the conclusion that it's a same kind of enzymes leading to the brown stain in the two konjaks.4. When we researched the influences of the temperature, the pH values,and the inhibitor of different concentrations on the activity of the polyphenol oxidase, the experents showed that the proper temperarure of the white konjak's polyphenol oxidase is about 35℃, whereas the other's 30 ℃ or so. When incubation 30min above 100℃, the activity of the white konjac is decreased by 95%, whereas the A.mairei decreased by 99.5%. The optimum pH values of the PPO (polyphenol oxidate) is 5~5.5, and below 2.2 or above 8 the activity is loss totally. And the activity of the PPO will loss in the gross when the concentration of the phytic acid is 6‰ above, and the concentration of the L-cysteine is above the 0.04‰~0.07‰, and the concentration of the citric acid is above 9‰ ~10‰, and the concentration of the ascorbic acid is above 0.1‰~0.12‰.5. After adopting four single factor inhibitors and combined inhibitor in treating with the them, we roasted them at 60℃. Then the results showed that the white konjac can reach the acceptable white of color when the L-cysteine's concentration is 0.01%, and the citric acid is 3%, and the plant acid is 0.5%, make the white konjac diping in them 5min. whereas the A.mairei need theL-cysteine's concentration reaching at 0.5% and diping in 5min .The concentration of the L-cysteine at abve 0.35%, and the citric acid 1%, then with the inhibitor together dip in 5min, the A.mairei 's color can be acceptable. And the concentration of L-cysteine 0.15%, the citric acid 1%, the phytic acid 2%, etc. Four groups can make the A.mairei reach the acceptable chroma.6. We found that all the management above are reasonable also when taking the polyglucomannose into grant. |
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