Bacterial histamine formation in mackerel and albacore was studied by inducing
histamine in the muscles under controlled storage conditions. The optimum temperature
for histamine formation was 25°C. The highest level of histamine detected was 283
mg/100 g in the 2-day stored mackerel; and 67.1 mg/100 g in the 6-day stored albacore.
To identify the bacteria crucial to histamine formation, histamine formers were isolated
using the conventional culture method. Enteric bacteria were most frequently isolated
from the fish. Weak histamine formers were found in the gill and skin of fresh fish, and
they required the enrichment step. Prolific histamine formers were mostly isolated from
the decomposed muscles during storage at 25°C. Morganella morganii was the most
prolific histamine former, producing >3,000 ppm in culture broth. M. morganii was the
most prevalent histamine former in mackerel. In albacore, however, the most prevalent
species was Hafnia alvei, a weak histamine former, resulting in less histamine
accumulation than mackerel. Weak histamine formers, identified as natural bacteria in
the marine environment, were found in mackerel during storage at 4°C after fish became unsuitable for human consumption. At 0°C, neither histamine-forming bacteria nor
histamine was detected in fish.
M. morganii formed significant amounts of histamine (>200 mg/100 g) in
artificially contaminated fresh and frozen mackerel, albacore, and mahi-mahi when the
fish were improperly stored at ambient temperatures (25°C). Growth of M. morganii was
controlled by storage of fish at 4°C or below, but histamine formation was controlled
only during frozen storage. For rapid detection of M. morganii, a PCR assay was
developed by designing 16S rDNA targeted primers. Unique primers found for M.
morganii were: the forward primer, 5'-CTCGCACCATCAGATGAACCCATAT-3'; and
the reverse primer, 5'-CAAAGCATCTCTGCTAAGTTCTCTGGATG-3'. Nine CFU/ml
of M. morganii inoculated in albacore homogenate were detected with a 6 h-enrichment
of samples in TSB at 37°C.
It would be necessary to monitor the presence of M. morganii in fish during
handling and storage due to its high histamine-producing capability and prevent its
contamination and proliferation after capture. The PCR assay developed in this study
would be helpful to routinely monitor its presence in fish. / Graduation date: 2002
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/25939 |
| Date | 14 August 2001 |
| Creators | Kim, Shin-Hee |
| Contributors | An, Haejung |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
Page generated in 0.0019 seconds