Agriculture Reference
In-Depth Information
irradiated must bear both the radura logo and a statement that the food has been
“ treated with radiation ” or “ treated by irradiation. ”
Effective reduction of microbial load requires doses higher than for the other major
purposes, and will therefore exert a larger effect on produce quality and shelf life
(Farkas and others 1997). Currently, cold chain integrity and modifi ed atmosphere
packaging (MAP) are the primary means of ensuring the quality of fresh produce after
it leaves the packing or manufacturing facility (Sumner and Peters 1997; Niemira and
others 2005). Improper or excessive treatment of fresh produce can lead to changes
in fi rmness, aroma, color, or taste (Yu and others 1996; Mahrouz and others 2004).
Delayed effects on phytoplane microbial ecology, including behavior of contaminating
pathogens, is also an important consideration (Prakash and others 2000a; Niemira and
others 2004; Lacroix and Vigneault 2007). Irradiated fresh produce must adhere to
accepted GAP/GMP guidelines for preservation of quality and food safety.
Quality of Irradiated Produce
Many studies have demonstrated that most fresh-cut fruits and vegetables irradiated
at doses of 1 kGy or less did not exhibit any signifi cant change in appearance, texture,
fl avor, or nutrient quality (Fan and Sokorai 2002a,b; Fan and others 2003a-c; Khattak
and others 2006; Kim and others 2005; Yu and others 1995). Shelf life of some fresh-
cut fruits and vegetables can be extended by low-dose irradiation due to the reduction
of spoilage microorganisms. For example, Koorapati and others (2004) showed that
irradiation at doses above 0.5 kGy prevented microbial-induced browning and blotch-
ing of sliced mushrooms. Studies have also shown that irradiated fresh produce may
have higher antioxidant content than nonirradiated controls as irradiation increased
synthesis of phenolic compounds (Fan and others 2005a).
In some fresh-cut fruits and vegetables, irradiation may cause softening and loss
of ascorbic acid (Fan and others 2008b). However, the adverse effects on texture and
ascorbic acid due to irradiation are often small compared to variation among cultivars
and the changes in storage (Fan and Sokorai 2002a).
Irradiation at higher doses (above 1 kGy) often caused an increase in electrolyte
leakage of many fresh-cut fruits and vegetables, an indication of cell membrane
damage. The increased electrolyte leakage, which may result in a soggy and wilted
appearance of leafy vegetables, varies among vegetables. In a study of thirteen veg-
etables, Fan and Sokorai (2005) observed that red cabbage, broccoli, and endive had
the lowest increases in electrolyte leakage; celery, carrot, and green onion had the
highest increase in leakage.
The losses in quality due to irradiation can be minimized by combination with other
sanitizers or techniques such as MAP, heat treatment, calcium infi ltration, and anti-
browning agents (Prakash and Foley 2004; Niemira and Fan 2006). For example,
Boynton and others (2006) showed that fresh-cut cantaloupes irradiated at 1 kGy in
MAP of 4% O
2
, 10% CO
2
had the highest rating in sweetness and cantaloupe fl avor
intensity and lowest in off-fl avor after 17 days of storage compared to the control and
0.5 kGy samples. Foley and others (2004) combined chlorine (200 ppm) with low-dose
radiation to eliminate
E. coli
O157:H7 on cilantro and found that the combined treat-
ment signifi cantly reduced levels of the pathogen on fresh cilantro while maintaining
