Irradiation - Food Shelf Life Stability: Chemical, Biochemical, and Microbiological Changes - page 110

but minimal change in starch degradation at this level. Leszczynski et al. 238 studied
the effect of irradiation at 150 Gy on potato quality and chip production. They found
that the irradiated samples were lower in starch and higher in sugar levels along
with some flesh darkening. All stored samples showed complete inhibition of sprout-
ing, whereas in the controls sprouting and related changes in composition increased
with duration and temperature of storage. Quality of chips depended on storage
temperature and only slightly on irradiation. Diehl 239 reported that irradiation of
potato slices followed by refrigerated storage instead of using freezing and frozen
storage would save the industry an estimated 300 million kwh of energy. He further
reported that in Germany consumer testing of potatoes irradiated at 120 Gy showed
a preference for the treated samples over the controls, particularily after 3 to 5 months
storage. Cumming 240 found similar results for yams irradiated at doses from 0.5 to
5 kGy, with the optimum dose for color preservation occurring at 2 kGy. A 100-fold
reduction in surface microbes occurred at this dose level. Adesuyi and Mackenzie 241
reported excellent sensory results and reduced rotting from irradiation of Nigerian
yams at 75 to 125 Gy for antisprouting purposes. Later work on sweet potatoes
showed significant increases in sugar concentrations even at doses of 0.1 kGy. 242,243
The sweeter irradiated samples were not preferred to the controls, in part due to the
darkened appearance of the treated samples, especially after baking.
Diehl 244 and other workers 245 have reported that low dose irradiation (50 Gy to
5 kGy) prolonged the storage life of onions for 9 months, mainly due to inhibition
of sprouting, but did not prevent rotting. Later work 246,247 has also shown that neither
gamma irradiation or long-term storage affected DM content or acidity, although
the intensity of flavor was affected and carbohydrate content decreased significantly
after 180 days storage, while ascorbic acid content remained unchanged. The irra-
diated bulbs were judged to be of superior appearance and firmness after 180 days
storage and showed no difference in odor. Similar results have been reported for
garlic irradiated at doses from 50 to 150 Gy with up to 80% reductions in spoilage
of the cloves after 9 months storage. 248
Yusof 249 reported that low dose irradiation of 25 to 80 Gy inhibited sprouting
in ginger but did not extend the shelf life. For cauliflower and broccoli, low dose
irradiation accelerated respiration which led to increased spoilage on storage even
under CO 2 . 228,250,251
Irradiation can be used to control Listeria monocytogenes in pre-cut bell peppers
and carrots. 254 Microbiological shelf life of bell peppers was doubled after irradiation
with 1 kGy and when coupled with GMP (Good Manufacturing Practices) practically
eliminated this pathogen from peppers. For carrot cubes, irradiation drastically
reduced the microbial load which improved the microbiological shelf life, whereas
irradiation of peppers at this dose caused an initial loss of 12% of ascorbic acid
followed by a further reduction of 10% during storage, this being comparable to
that occurring in the controls. After 10 days of storage, the -carotene content of

the irradiated samples of both products was slightly higher than that of the untreated
samples. Previously it has been reported that doses greater than 1 kGy caused
excessive softening of the tissue. 253 Cathalin and McNulty 254 have reported losses
in texture in carrots, apples, and potatoes ranging from 5 to 30% at doses ranging
from 0.3 to 1.0 kGy. Carrots were the most resistant to irradiation induced textural

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