Pacific oysters (Crassostrea gigas), Alaska pink salmon (Oncorynchus
gorbuscha) roe and chum salmon (Oncorynchus keta) fillets were treated with
aqueous ozone in both pilot plant and commercial settings to determine its effect on
shelf-life and microbial changes. The microbial quality was analyzed by conducting
pyschrotrophic and coliform plate counts on 3M petrifilm. Oxidative rancidity, pH
and moisture were measured during the shelf-life study to determine the effects of
ozone on quality. Concentrations of 0.5-1.3 ppm of ozone were applied for periods
of 30 s, 1, 2 and 4 min at 5°C, 9°C and 15°C to determine an optimum ozone
concentration and contact time that would decrease the seafood microbial load and
increase shelf-life in the pilot plant studies. Oysters and roe were treated at 15°C
and 5°C and fillets were treated at 9°C.
There where only minor microbial differences between ozonated and non-ozonated
samples. Treatment temperatures rather than treatment types affected the
microbial load. The pilot plant experiments at 15°C and 5°C showed 1 log
decrease in oysters and roe treated with aqueous ozone at variable concentrations.
No increase in shelf-life was observed when salmon fillets were treated with
aqueous ozone (1.3 ppm) for 2 min. Bacteria strains were isolated from treated (ozone
and water) and control salmon fillet groups at 0, 5 and 10 days of storage and identified
using the API20 NE system. The microbial change in the fillet flora did not differ between
ozonated and non-ozonated treatment groups. Gram-positive bacteria were predominant
in all groups at day 0, Pseudomonas flunrescens and P. putida were the predominant
bacterial species found from all groups at days 5 and 10.
Aqueous ozone (0.5-1.7 ppm) was applied in a commercial Ikura roe processing
facility. A decrease in the microbial load was seen in the pre-processed samples which
were ozonated with eggs in the skein. There were no differences in microbial loads from
the non-ozonated and ozonated post-processed samples of individual eggs removed from
the skein. / Graduation date: 2003
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/27123 |
| Date | 20 May 2002 |
| Creators | Hansen, Jenny K. |
| Contributors | Morrissey, Michael T. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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