Effect of 60Co Irradiation on the Degumming of Bast Fiber

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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.
日本食品照射研究協議会の論文

Effect of <SUP>60</SUP>Co Irradiation on the Degumming of Bast Fiber

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日本食品照射研究協議会 | 論文

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