258 Produce Degradation: Reaction Pathways and their Prevention
radiation can inhibit sprouting in potatoes and other foods and slows the ripening
and spoilage process of fruits. High doses of radiation cause side effects in the
produce such as an objectionable flavor, texture, and color. For this reason, a low-
dose radiation process has been accepted as a useful technique to extend shelf life
of fresh foods, particularly when used in conjunction with refrigeration and other
auxiliary methods of preservation.
The effect of radurization on produce quality has been widely researched. In
some fruits and vegetables, radurization resulted in a decline of flavor during storage.
However, in others no effect on flavor was observed (Thayer, 1990; Salunkhe et al.,
1991). For example, irradiation of potatoes, onions, carrots, and many other fruits
and vegetables produces no detrimental effects on flavor (Salunkhe et al., 1991).
Radurization cannot inactivate enzyme systems in plants. Consequently, irradiated
fresh fruits and vegetables are prone to enzymic deterioration unless they are
blanched prior to radurization. Also, during redurization, complex components of
food such as fats, proteins, and carbohydrates (starch, sugar, inulin, cellulose, and
pectin) are degraded to their simpler components. This degradation of some complex
components has been attributed to a change in texture, especially the softening of
produce. Radurization also destroys the green color in treated vegetables. Increasing
the gamma radiation dose over 0.5 kGy results in a linear decrease in the chlorophyll
content of green beans and broccoli. Irradiation has also been shown to cause 5 to
95%, 3 to 20%, and 0 to 5% destruction of carotenoids in broccoli, sweet potatoes,
and carrots, respectively (Thayer, 1990; Salunkhe et al., 1991). Radurization also
can lead to more than an 80% loss of vitamin C in green vegetables such as asparagus,
broccoli, green beans, and spinach. The loss of some vitamin C was dependent on
the irradiation dose and the variety/species of the produce. Vitamins A, C, and E are
sensitive to gamma radiation, with higher doses causing more loss. Losses of vitamin
C in oranges, tangerines, tomatoes, and papayas varied from 0 to 28% with an
increase in radiation doses from 40 to 400 kGy (Thayer, 1990; Salunkhe et al., 1991).
A review of the research related to the safety and nutritional adequacy of irradiated
foods conducted by the World Health Organization (WHO) concluded that radur-
ization is a good process for reducing or eliminating pathogens and spoilage micro-
organisms in foods (WHO, 1994). However, certain nutrients might be more sensitive
to loss, such as vitamins A, C, and E. Radurization has potential applications in
extending the storage life of fresh fruits and vegetables.
8.11 SUMMARY
Nutrient loss in fresh produce might occur at a number of different levels in the path
from “farm to table.” Therefore, both pre- and postharvest stages of produce have
to be taken into consideration. It is also important to note that in addition to treatment
of produce, or lack of it, environmental conditions, type of produce, and type of
nutrient are important factors to take into consideration. Produce handling and close
monitoring at all times is important to ensure that the closely interwoven physical
and nutritional quality are maintained for the maximum benefit of all the key produce
handlers: the consumer, producer, processor, and retailer.