Studies on Maturation Changes in Fruits induced by Ionizing Radiation. III:The effects of gamma radiation on the ripening and the keeping quality of astringent persimmons

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The suitability of ionizing radiation as means of regulating the fruit ripening has been investigated. There are also a few reports on the removal of the astringency in Kaki fruit by gamma radiation. The present paper reports the differences among the varieties and the effects the dose levels on the removal of the astringency by gamma radiation, and its physiological changes was also investigated. The varieties of 'Hiratanenashi', 'lMiyazakimukaku' and 'Atago' were primarily used in the experiments, and two varieties of 'Yokono' and 'Hagakushi', were used in part. Tie fruits were irradiated at the doses from 1.5×105R to 4.0×106R by gamma rays from Co 60 at the dose rate of 2.5×105 R/h.The temperature durimg the storage was at 20°C or at room temperature for the storage of 'Yokono' and 'Hagakushi' fruits . With 'Hiratanenashi' variety, the fruits irradiated at the doses less than 1.5×105R had no change in the appearance immediately after irradiation. However, the fruits irradiated at the dose of 4.0×106R lot became very soft and dark-brawn in color, and they had almost no-astringency. The fruits irradiated at the doses of 1.5×105R and 2.5×105R ripened 3 to 5 days after irradiation, accomparried by the removal of the astringency (Fig.1).However, the following is of special interest in this experiment. The softening of the flesh and the astringent removal during the storage were less at the doses of 1.0×106R than at the doses of 1.5×105R, 2.5×105R and 4.0×106R, though these changes were greater immediately after irradiation as the radiation dosage increased. Such tendency was also observed in 'Miyazakimukaku' and 'Yokono' varieties (Table 1). In 'Atago' variety, the flesh of the irradiated fruits softened immediately after irradiation and during the subsequent storage with increased level of the radiation dose. The soluble tannin content rapidly decreased and the contents of acetaldehyde (Table 2) and soluble pectin increased in the irradiated fruits which became soft immediately after irradiation or during the storage. Ascorbic acid content decreased with higher dose. From the results of the separation of free amino acids by using the thin layer chromatography, the composition of amino acids appeared to be unaffected by gamma radiation (Fig.2). The CO2 production rates of irradiated fruits sharply and temporarily increased immediately after irradiation and gradually declined thereafter. The rates of this initial increase in CO2 production were proportional to the dose level up to the dose of 1.0×106R (Fig.3).
日本食品照射研究協議会の論文

Studies on Maturation Changes in Fruits induced by Ionizing Radiation. III:The effects of gamma radiation on the ripening and the keeping quality of astringent persimmons

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日本食品照射研究協議会 | 論文

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