Irradiation - Food Shelf Life Stability: Chemical, Biochemical, and Microbiological Changes - page 106

counts. Although a slight radiation odor was detected in samples treated with a 2 kGy
dose, it was suggested that other products including smoked ham, which has a more
robust aroma, would be more suitable. Irradiation in regards to microbial safety in
processed meats including bacon and ham is given by Anellis et al. 185,186 and Thayer
et al. 187 while sensory evaluation of radiated treated frankfurters as impacted by
phosphates and nitrites is given by Terrell et al. 188
F RUITS AND V EGETABLES
Fruits
During the past 30 years there have been many studies on the application of irradi-
ation for improving shelf life of fresh fruits. These include tropical fruits such as
bananas, mangos, and papaya; subtropical fruits such as citrus and grapes; and
temperate fruits such as pome fruits, stone fruits, and berries.
Gamma irradiation at low dose levels has been shown to improve shelf life of
bananas, mangos, and papaya by delaying the ripening process and these dose levels
have been found to be effective as a quarantine treatment against fruit flies and
mango stone weevil infestations. 189
Cumming reported recently that low-dose radiation (0.2 kGy) delayed ripening
of green bananas for up to 10 to 12 days. 190 There was only minimal changes in
pulp texture and vitamin C losses were lower than the controls. Earlier work by
Ferguson et al. 191 showed retardation of yellowing at a dose of 0.2 kGy and an
increased preference for the flavor of the irradiated bananas 7 days after treatment.
Thomas reported on shelf life extension of 10 to 12 days for some varieties. 189
Several studies have shown that gamma radiation at low levels extends the shelf life
of mango fruit by slowing down rates of ripening and senescence. Irradiated fruit
remain edible for longer periods before they pass into the senescence phase, thus
improving the overall market life of the fruit. 189 Mangos and papaya are irradiated
mainly to delay ripening and for disinfestation. 192 The irradiated fruit can be detected
by GC-MS analysis of the TCB (2-tetracyclobutanone) peaks present in lipid extracts
from the fruit. This has proved to be a better method of analysis for irradiated fruit
than ESR spectroscopy. Willemot et al. 193 recently reviewed the applications of
gamma radiation to the preservation of mangos, papaya, and strawberries, while
others 194 studied the effects of irradiation and a combination of hot water dip-
treatment plus irradiation on the storage, sensory, nutritional physical characteristics,
and biochemical changes in mangos. They reported that irradiation alone reduces
respiration and color development and increases fruit softness, but did not signifi-
cantly affect sensorial quality. They also reported that the combined treatment of
hot water and irradiation had a synergistic effect on increased shelf life of mangos
up to 32 days, without affecting nutritional quality. 195-199 Furthermore, they found
that the combination treatment was more effective in post-harvest decay control than
irradiation alone. Paul 200 reported that irradiated Hawaiian papaya softened more
uniformly than the controls, and for fruit irradiated with 30% of the skin yellowed
softening was at a slower rate. Irradiation 201 at the 15 to 30% yellow stage resulted
in no significant change in skin and pulp color, or pectin methyl esterase activity.