Biomedical Engineering Reference
In-Depth Information
by about 3 months if maintained under refrigerated storage. In contrast, a previous
study on the sensory properties of radiated smoked white fish (less fatty compared
to salmon) concluded that dosages from 3 to 5 kGy had no adverse impact on flavor
and texture. 124
Although the sensory properties of dried sardine and flounder were not assessed
following a 5-kGy treatment, Ito and Abu 125 reported that based on reductions in
putrefactive microorganisms, such as Pediococcus halophilus , Vibrio costicola , and
Planococcus sp. product shelf life in polyethylene pouches could be extended 2 to
4 times. This represented a storage period of approximately 2 months.
Fish mince, which serves as an intermediate raw material for the manufacture
of various analog seafood products, is a further example of a processed fishery
product that has been investigated using radiation. 126 Since a major portion of the
processed fish mince is preserved by freezing, cryoprotectants including carbohy-
drates are frequently incorporated to reduce protein denaturation. The application
of radiation was investigated as a means of pasteurizing the mince, thus eliminating
the need for freezing and the inclusion of a cryoprotectant. Following treatment with
0.66 and 1.31 kGy a taste panel concluded that the shelf life of the radiated mince
could be extended by about 12 and 18 days, respectively, when accompanied by
storage at 3.3°C. Based on a cut-off of 10 6 cfu/g, a level established by the sensory
panel which coincided with unacceptable product, the microbiological quality of the
mince was extended by 6 and 13 days, respectively. However, a functional property
of the mince, specifically the gel strength, decreased following treatment. This
decrease appeared to be dose-dependent.
Shellfish
Early studies for the preservation of shrimp involved the use of chloretracycline
(CTC) with radurization as a means of lowering the treatment dose. 105,127 During
refrigerated storage over a period of 8 to 10 weeks, it was reported that radiation at
5 kGy with 5 ppm CTC was just as effective in extending the shelf life as treatment
with 7.5 kGy.
Gamma radiation of fresh refrigerated shrimp using doses between 5 and 7.5 kGy
extended freshness four- to fivefold. 127,128 However, the latter dose contributed to
odor which apparently decreased during product storage. When fresh, peeled shrimp
was maintained at an abusive temperature of 10 to 12°C following 1.5 and 2.5 kGy
treatment, the storage life was extended by 10 to 14 and 20 days, respectively.
However, at a storage temperature of 2 to 4°C, the shelf life was extended 21 and
25 days, respectively. A blanch treatment involving steaming for 4 min followed by
treatment with 1.5 kGy resulted in a sensory acceptable product following 60 and
130 days storage at 10 to 12 and 2 to 4°C, respectively. Further, treatment at this
dose did not result in fading of astaxanthine, the characteristic pigment found in
fresh shrimp. In terms of color, taste, and odor, shrimp treated at 1.5 kGy scored
similar to non-irradiated controls. Gamma radiation of fresh prawn at 1.45 kGy
resulted in about a 1 log reduction in total counts and a 1.3 log reduction in
proteolytic microorganisms. Increasing the dose to 2.5 kGy brought about larger
reductions of 2.5 and 2.2 log, respectively. 129 During storage for 28 d at 1°C,
 
Search WWH ::




Custom Search