chlorogenic acid (CGA) and caffeic acid (CA) in lyophilized potato tubers were quantitatively determined by high performance liquid chromatography (HPLC), and the changes in CGA contents of γ-ray-irradiated potato tubers (100 Gy) during storage at 25°Cwere studied.
The CGA contents of the irradiated potato tubers slightly increased immediately after irradiation, but decreased gradually after 29th day and reached the same level as that in the beginning of storage on the 73rd day after irradiation. However, the CGA contents of the unirradiated potato tubers increased steadily with increasing days of storage period, and reached twice that in the beginning of storage on the 73rd day after irradiation.
The CGA contents in potato tubers determined by Diazo and Folin-Denis methods were shown to be two - eight times higher than those by HPLC method, and there appeared to be no significant relation between the CGA contents determined by HPLCmethod and by colorimetrical methods.

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It is well known that the sprouting of potato tubers is inhibited through the irradiation of 100 Gy (10 krad) in open air, but in the case of same dose irradiation in nitrogen gas or carbondioxide gas, the sprouting cannot be inhibited and in these gases much more doses are necessary for inhibition.
In this report the respiration of the potato tubers irradiated in nitrogen gas or carbondioxide gas was studied.
Potato tubers of common Japanese variety, “Danshaku” wereused for the examination. Potato tubers of about 2 kg were put into each of Triple-Nylon bags and the bags were sealed after replacement of air in bags with nitrogen or carbondioxide gases. More than 16 hours after sealing of bags, the γ-dose (⁶⁰Co) of 150 Gy or 250 Gy were given to the potato tubers in bags at the dose rate of 10⁴R/h. After irradiation, all bags were opened in air and amounts of CO₂released by respiration of tuberswere measured with Hitachi gas chromatograph analyserType 023.
The amounts of CO₂released from the potato tubers irradiated in open air is shown in Fig. 2. The results show that there is an initial lag period of several hours, followed by a rapid increase in the respiration, after which the CO₂release was gradually decreased.
Potato tubers irradiated in nitrogen gas show a similar release of CO₂on time scale to the potato tubers irrad iated in open air, but the total amounts of CO₂are approximately half of those of the potato tubers irradiated in open air (Figs. 3 and 4).
When the bags which enclosed potato tubers in carbondioxide gas were opened in air after irradiation, much CO₂was released from the tubers (Fig. 5). The difference of the CO₂release between irradiated potato tubers and non-irradiated ones is considered the increase of respiration of potato tubers irradiated in carbondioxide gas (Fig. 6). The increase of respiration of potato tubers irradiated in carbondioxide gas is more slowly and less than that of potato tubers irradiated in open air.

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