The fruits of Citrus Unshiu which were almost ripened were harvested at November and were stored for 15 or 18 days at 20, 10and 4°C, and were irradiated from both of the stem-end and another end by the electron beam of a Cockcroft-Walton type accelerator at the 300 KeV with dose of 150 Krad (± 25%).The situation of fruits stored was observed at the storage temperature of 20, 10 and 4°C before and after irradiation.
Figures 1 and 2 show the appearance of browning of peel. The appearance of browning of peel are slight for Citrus Unshiu(late variety) which were stored at 20°C before or after irradiation and which lost the weight hastily (Fig. 1). For the others, the browning of peel appeared more strongly and more early at the higher temperature of storage before or after irradiation. For the early variety of Citrus Unshiu (Fig. 2), the browning of peel are observed to be stronger at the higher temperature of storage before irradiation, and to be slighter at the smaller difference of temperature between before and after irradiation. It seems likely that the browning of peel appears more early at the higher temperature after irradiation. Beside these experiments, it was observed that the browning of peel appeared on all fruits irradiated at 1 or 7 days after harvest. It has been reported for potato bulbs irradiated that the increase of respiration was related to the browning of fibro-vascular regions. It is considered similarly that the appearance of browning of peel is related to the respiration of fruits under the several temperature conditions after irradiation.
The results for the effect of electron irradiation on the browning of fruits wrapped with the film of cellulose acetate or dampproof cellophane are shown in Fig. 3. For the late variety, the browning of peel wrapped with film is not remarkable and appears for more number of fruits comparingwith non wrapped ones. It was observed generally that the degree of browning of peel was strongest on about 30 days after irradiation under 4°C and faded slightly with storage time.
Figure 4 shows the results of the rate of browning by the different electron accelerating voltage. The difference of the rate of browning is slight between 300 and 500 KeV, and it would be said that the rate of browning is smaller for 500 KeV than 300 KeV. Beside these, in the preliminary test that an alminium plate was set at the front of irradiation window and the irradiation was done with the dose of 150 Krad at 114 KeV, the browning of peel did not appeared so strongly.
The situation of storage at 29th, March (4 months after irradiation) are shown in Table 1. It is not good for the fruits stored under the temperature of 10°C before irradiationand 20°C after irradiation. This ones are larger in the loss of weight and wilted. The fruits wrapped with cellulose acetate film are not good and the numbers of rotted fruits are more comparatively with the results in last year. In the tests, No. 2 and 3, of Table 1, the numbers of fruits deteriorated or infected with fungi are less for the irradiated than for the non-irradiated fruits.
From these results, it was recommended for the storage of fruits of Citrus Unshiu that the fruits harvested were immediatedly cured at 4°C until the weight loss of 3%, and stored at 4°C in a basket which was piled up to ten baskets and was surrounded with a corrugated cardboard sheet to prevent from being exposed directly to cool wind.

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This investigation was undertaken as a basic experiment to discuss the radiolysis of lipids in food irradiation.
Many experiments have been made on the effect of ionizing radiation on fatty acids, natural fats or oils, and foods which contain much fat or oil. Following analyses of those irradiated samples were various according to the purpose.
In this paper, methyl esters of fatty acids-methyl stearate (C_18:0), methyl oleate (C_18:1), methyl linoleate (C_18:2), methyl linolenate(C_18:3), methyl arachidate (C_20:0) and methyl arachidonate (C_20:4) were irradiated in n-hexane solution in attempt to obtain larger changes by lower dose. On radiolysis of n-hexane which would be expected to take place, repoTts by Dewhurst, Hardwick, Windmer and his coworkers, Shida and his coworkers and Kimura and his coworkers were referred.
Prior to experiment methyl esters of fatty acids were purified by recrystallization or urea complex method or bromination. The hemical purities of these esters assayed by GLC analyses were 94-99%. Each solution was sealed in glass ampule and rradiated with 60Co-γ ray at room temperature. Conditions of γ-irradiation and items of analysis were shown in Table 1.
Analyses employed in this examination were GLC, IRspectrometry and determination of IV.
In GLC analysis, solution was injected directly after cutting the ampule. Conditions for GLC analysis were shown in Table 2.
Preparations for IRspectrometry and IV determination were the oils obtained by vacuum evapolation in N₂gas stream. IR-spectra were examined with KBr pellets. IV determinations were carried by Wijs method.
Two gas chromatograms were shown in Fig. 1 and 2. Methyl stearate was the most stable and methyl linoleate was the most labile. In the gas chromatogram of methyl linoleate appeared unidentified peak (peak 1). Decreasing curves of methyl esters in n-hexane solution with the increase of dose were shown in Fig. 3. Remains of esters presented by peak area and remaining ratios at 7.1 Mrad irradiation were shown in Table 3 and Fig. 4.
There were some generalizations in IRspectra of irradiated and unirradiated-esters. In high dose level, the bands at 1670 cm^-1were decreasing and the bands at 970 cm^-1were more intensive (Fig. 5). The bands around 1670 cm^-1were due to the double bond system of carbon and those at 970 cm^-1the trans configuration. These observations were indicative of the occurrence of any changes at double bond system and of isomerization from cis to trans configuration by γ-irradiation.
IV of four esters were shown in Table 4. The values of methyl stearate were unchanged and nearly zero at any dose. Those of unsaturated esters were diverse and showed no equal tendencies. However, these observations were not well understood, they agreed with the results of Bancher reported that IV of irradiated oleic acid and linoleic acid varied irregular with increase of dose.

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As described in our previous paper, increased dose of γ-radiation caused a progressive increase in the total extractable pectic substances and a gradual decrease in the polymerization degree of cellulose in the case of ramie raw fiber. However, at present few papers have been published about the difference of radio-sensitivit between pectic substances and cellulose. Kertesz et al, in their studies on the softening effect of γ-radiation on apples, carrots and beets, stated that pectin was somewhat more susceptible to degradation by ionizing radiation than does cellulose.
In degumming bast fiber, gummy substances consisting mainly of pectic substances are removed by natural fermentationor alkali treatment. Consequently, irradiation of ⁶⁰Co may be an attractive means for pre-degradation of pectic substances in degumming process of bast fiber.
Dried flax straw (Sample A, harvested in Uzitsu, Formosa, 1971) were irradiated with ⁶⁰Co at 6 dose rates, 0 to 10.0 Mrad, then subjected to degumming processes.Table 1 showed data obtained from this experiment. The dose of 0.5 Mrad was not extensive enough to give remarkable effects on the quality of fiber, but doses of 1.0 Mrad or above resulted in a severe effect on the fiber yield and splitting of fiber strand.
Further experiments which comprise 3 radiation doses;0, 1.0 and 5.0 Mrad were performed on sample B (harvestedin Shoka, Formosa, 1971) to elucidate the effect of ⁶⁰Co irradiationon degumming of bast fiber especially to study the behavior of pectic substances and quality of fiber. (Table 2) As shown in Table 3, progressive decrease of protopectin were observed with increasing of pectin and pectic acid as increased dose of ⁶⁰Co.
Gelfiltration pattern of pectic substances in waste water of degumming process on Sephadex G-75 showed that pectic substances distribute in the lower molecular region at natural fermentation, but in somewhat higher molecular region at chemical treatment, and this pattern of chemical treatment shift gradually to the lower molecular region with increased dose of ⁶⁰Co. (Fig. 1)
The changes occurred in the quality of fiber were shown in Table 2 and Fig. 2. Fiber length became gradually shorter, denier of fiber fine and fiber strength weaker with the increased ⁶⁰Co dose, but no detectable effect were found within 1.0 Mrad dose.
From the result of present and previous papers, it is clear that degradation of pectic substances occur clearly at the ⁶⁰Co dose of 0.1 - 0.5 Mrad, but damage of cellulose are not so remarkable. Consequently, it may be an interestingmeans to irradiate 60Co prior to degumming of bast fiber, especially as mix-spinning materials with synthetic fiber, because degradation of fiber to some extent may be allowed in the mix-spinning, and moreover radiation can be expected to prevent the rottenness of materials.

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