HISTOCHEMICAL ANALYSIS OF γ RADIATION EFFECTS ON RUBUS FRUITS
Pasteurization by rays is an important method óf preserving foods. However, it appears that the treatment has a significant effect on the irradiated material. For three years we have been working on radiation effects on the cell wall polysaccharides of pulp from several fruits. As part of this work we irradiated two batches of raspberry (cv 'Willamette') at 10 and 100 kr and then compared them with a non-irradiated control. Separate samples of irradiated and non-irradiated fruits were fixed at 0, 24 and 48 hrs after the time of irradiation and their cell wall content histochemically analysed by a specially devised method (Jona and Foa, in press): stepwise extracted tissues were PAS stained and the intensity of the cell wall colour measured by a cytophotometer, thereby estimating the polysaccharide content of the cell walls. As with other fruits it appeared that 100 kr of irradiation increased the amount of total polysaccharides in the fruit cell walls during the first 24 hrs after treatment, largely due to an increase in pectic substances. However, after 48 hrs the amount was less than in the non-irradiated controls.
It is not easy to explain the results, but it is likely that they are caused by interference with enzyme metabolism through an effect on DNA dependent RNA, rather than by direct breakdown of polysaccharide molecules.
Jona, R. and Vallania, R. (1976). HISTOCHEMICAL ANALYSIS OF γ RADIATION EFFECTS ON RUBUS FRUITS. Acta Hortic. 60, 81-88