リンゴ果実のメタボリズムと揮発性成分に関する研究アルデヒドとヤケ病発生機構

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1. Apple scald is known as the breakdown of fruit peel during the storage, the cause of which has been attributed to the effect of certain volatile substances, especially esters, produced by the meta-bolism of the fruit tissue. However, the detail as to causal volatiles and the mechanism of their ge-neration is very little known, The present inves-tigation was planned to see the response of stored apples to various gasses, having possibility to be emanated through senescence and to determine their effect on the respiration of the fruit tissue, so as to make it possible to deduce what kind of metabolism should have been taken place within the fruit to initiate such a breakdown of the peel tissues. The materials used constituted of “Rails” apple from tree or stored as long as six months after harvested at the Shinshu University, Nagano Prefecture, and random picks from local retailers representing varieties of Yellow Transparent, Mc-Intosh Red, Starking, and Jonathan. 2. Gasses generally believed to have been emitted from apple fruits during the storage, are ethylene, acetaldehyde, alcohol, and ester. Esters were not used from the reason that THOMPSON and HUELIN had proved in 1951 to be not the causal agency. The first lot of fruit was kept enclosed separately in ethylene of the concentration 100, 500, 1000 and 5000 ppm. The second lot was constituted of apples sealed in 1.5l desiccator with 4ml each of acetal-dehyde or 95% of ethyl alcohol. In the third lot, apples were enclosed in larger desiccators of the capacity of 10l in which vessels containing 1, 3 or 5ml of acetaldehyde were placed separately. Res-. piration in term of μl/g/hr was measured by WAR-BURG apparatus at the temperature of 30°C by using 0.5g of diced blocks of peel and pulp of apple fruit treated with gasses above mentioned. 3. Ethylene gas evidently gave an after-ripe effect in concentrations lower than 1000 ppm, but in 5000ppm fruits became softened and discolored, but not scalded, with reduced uptake of oxygen but without appreciable change in the phase of respira-tion, i.e., R. Q. being unaffected. Ethylene in ordinary concentration seems to be not causal agency. 4. Vaporized alcohol also gave no effect on the fruit. Acetaldehyde, on the contrary, gave response to an appreciable degree along with its accumulation, developing a symptom quite identical with the natural scald. At its high concentration (5ml) the tissue breakdown will reach into the innermost part leaving only upper portion unaffected within 10 days. 5. The respiration of acetaldehyde-induced scald tissues of both peel and pulp shows a considerable depression in magnitude of oxygene uptake and carbon dioxide output, and smaller R. Q. 6. Agencies reducing the activity of respiration enzymes, such as NaF, monoiodoacetic acid, and malonic acid, are added to the acetaldehyde treated tissue and compared with healthy apple not exposed to acetaldehyde in treating with these agencies. The percentage inhibition of oxygen consumption of artificially scalded apple was reduced nearly one half as much as.that of healthy fruit so treated, so that in the scalded apple the oxygen must have been consumed in some other way than ordinary respira-tion. This is proved by an addition of oxidation-reduction reactants such as l-ascorbic acid or pyrocatechol, through which respiration is greatly increased in sick fruits than healthy ones in vitro. 7. The addition of succinate gave almost identical effect to sound or sick fruit in vitro, while the pyruvate caused sick fruit to generate unusually large amount of carbon dioxide, more than twice as much as that of the sound fruit. Metabolism of sick fruit, therefore, seems not necessarily enclosed within tricarboxylic acid cycle but the large amount of pyruvic acid consumption may have contributed to produce excessive acetaldehyde
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リンゴ果実のメタボリズムと揮発性成分に関する研究アルデヒドとヤケ病発生機構

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