Gamma irradiation of potatoes: Effects on sugar content, chip color, germination, greening, and susceptibility to mold

Abstract

Russet Burbank potatoes that had been stored at 40°F. for 5 months after harvest were irradiated with 5,200 and 14,000 rad of Co60 gamma rays. In general, irradiation caused an accumulation of sugars. At 40°F., the sucrose level rose to nearly 3 times that of the control in 16 days following irradiation. Fructose and glucose showed smaller increases and the latter did not accumulate significantly in the tubers given the higher dose of gamma rays. At 70°F., the levels of sucrose and glucose in the irradiated tubers rose above those in the controls, the difference reaching a maximum in 4 days and then declining. Irradiation had no effect on loss of fructose at this temperature. Color of potato chips processed from the irradiated potatoes was in general darker than that of chips from control tubers. The storage-time pattern of color change resembled that of the reducing rather than total sugar. Fourteen thousand rad did not prevent initiation of germination in the tubers but did destroy their sprout-growth apparatus. Although the lower dosage did not prevent initiation and subsequent growth, it prevented the formation of secondary tubers, which appeared on the sprouted control tubers. Furthermore, unlike the controls, the low-dosage potatoes developed branching hair sprouts with no tendency toward apical dominance during the early stages of sprouting. The rate of greening of gamma-irradiated and illuminated tubers was significantly less than that of unirradiated illuminated controls. Evidence is presented that irradiation may increase the susceptibility of potatoes to attack by molds under some conditions.