Effect of Ionizing Radiations on Pectin

Abstract

The pectic substances play an important role in influencing the firmness, texture, and softening of many plant tissues, particularly fruits and vegetables (1). For this reason a study of the effect of ionizing radiations on pectin was made an integral part of our investigations of the irradiation-induced softening of plant tissues. The present paper reports the results of some model experiments which were designed to give information on the extent of irradiation which causes measurable changes in pectin. Pectin is basically a colloidal macromolecular polymer of anhydro-D-galacturonic acid (1). The changes which occur in macromolecular polymers on exposure to ionizing radiations have been observed in a number of instances, particularly with synthetic polymers and elastomers. It is quite clear that, with respect to the effects of ionizing radiations, macromolecular polymers fall into two categories (2). Compounds of the first group show, on irradiation, crosslinking or increased crosslinking. Polyethylene is a representative of this type of behavior (3). In the second group fall macromolecular polymers which are hydrolytically degraded by ionizing radiations. As far as is known today, naturally occurring polysaccharides like cellulose (4, 5), dextrans (6, 7), starch (8), agar (9), alginic acid (10), various gums (8), and pectins (11, 12) fall into this latter category. The literature contains some observations on the texture changes which occur on the irradiation of plant tissues (13, 14), but only a recent article of Roberts and