Irradiation - Food Shelf Life Stability: Chemical, Biochemical, and Microbiological Changes - page 94

This resulted in a further loss of tenderness compared to controls. In contrast, when
skinless and boneless chicken breasts were preserved using sous-vide and electron
beam radiation (2.9 kGy) moisture levels were not affected. 82 Neither appearance nor
tenderness of the samples was evaluated; however, based on microbiological results,
the application of radiation with sous-vide preservation compared to sous-vide alone
resulted in an additional 2-week extension in shelf life at 2°C. Doses from 1.1 to
2.9 kGy contributed to off-odors which were detected immediately upon opening
the package. Although the intensity of the off-odors appeared dose related, they
quickly dissipated and ostensibly originated from interactions arising between the
packaging material and the treatment. From a product safety standpoint, the com-
bination of sous-vide heating and radiation appeared more effective in reducing
listeriae than either treatment alone. 82 These results are in agreement with studies
which indicated that heating sensitizes pathogens including listeriae to radiation
treatment. 83 Further, the sensory quality of tray-packaged chicken breast meat main-
tained at 1°C following radiation at 3.8 kGy was acceptable for three weeks. 91 In
comparison packaged leg meat treated at 3.6 kGy and stored at 2°C maintained
eating quality for only 2 weeks. Although Katta et al. 62 reported that doses from
1.5 to 2.0 kGy resulted in a significant shelf life extension of refrigerated poultry,
Basker 91 indicated that the use of higher dosages might better inhibit microbiological
growth particularly on leg meat. Differences in the pH between leg (6.4 to 6.7) and
breast muscle (5.7 to 5.9) have been reported and are known to result in distinct
microbial growth patterns. 66
F ISH
Fish and Fishery Products
Compared to other food commodities, sensory evaluation of fish and seafood in
terms of quality and or freshness is mainly judged subjectively. Therefore, any
intervention treatment used to extend the shelf life must not diminish the character-
istic appearance, odor, texture, and taste of the product. Numerous tests have been
evaluated in order to assess fish quality. These include chemical: trimethylamine,
total volatile bases, measurements of oxidative rancidity; physical: electrical prop-
erties, pH, Eh, texture, water-binding capacity; and microbiological: standard plate
count, psychrotrophic count, coliform count methods. 101 Overall, however, no single
test has been shown to be useful when judging fish quality, although in some cases,
for specific situations or for a limited number of species or products, taste and odor
appear the most crucial. Low-dose radiation treatment, particularly in the range of
1 to 5 kGy, is especially effective in further extending the refrigerated shelf life of
various fish and fish products by reducing at least 90 to 95% of the original spoilage
microflora. Fresh fishery products processed in plants adhering to good manufac-
turing practices would be ideal for treatment. Conversely, stale fish or fish undergoing
visible spoilage would receive minimal benefit from such treatment. Radiation pres-
ervation when applied to fish has also been demonstrated to be an effective treatment
against specific pathogenic bacteria. 102 By eliminating and/or reducing pathogens,
radiation treatment can provide consumers with an increased margin of safety especially
for shellfish and raw fish products including sushi, which are routinely consumed