New Zealand Journal of Marine and Freshwater Research abstracts
Short communication
Survival of Escherichia coli in toroi: a traditional Maori food
L. Dixon
172 Horahora Road
Rd 2, Te Kauwhata, New Zealand
A. Donnison
Climate, Land & Environment Section
AgResearch
Private Bag 3123, Hamilton
email: andrea.donnison@agresearch.co.nz
C. Harfoot
I. R. McDonald
Department of Biological Sciences
University of Waikato
Private Bag 3105
Hamilton 3240, New Zealand
Abstract New Zealand lowland streams and rivers often contain elevated levels of faecal microorganisms, including disease-causing species and the indicator bacterium Escherichia coli. Filter-feeding shellfish can accumulate microbial contaminants particularly after extensive rainfall. Toroi is a traditional Maori food prepared from watercress or sow thistle (puha) and shellfish, often sourced from the wild. The mixture is refrigerated in screw-capped jars and usually eaten within 2 months. In this study, 10 batches of toroi were prepared from boiled watercress or puha that was mixed with chopped uncooked green-lipped mussels that were purchased from retail outlets. Portions of each toroi batch were experimentally contaminated with E. coli that was added at two initial concentrations, 0.72 E. coli g–1 and 604 E. coli g–1 . There was only an occasional detection of E. coli, in very low numbers, from uncontaminated toroi. In contaminated toroi, E. coli declined at similar slow rates at both levels of contamination. This slow rate of decline demonstrates that refrigerated storage should not be relied on as a protective mechanism against a risk of illness. Care should be taken to ensure the shellfish used in toroi are collected from sites that are free from faecal contamination.
Keywords green-lipped mussel; watercress; puha; sow thistle; water
New Zealand Journal of Marine and Freshwater Research, 2007, Vol. 41: 369–375
0028–8330/07/4104–0369 © The Royal Society of New Zealand 2007
M07023; Online publication date 20 November 2007. Received 22 May 2007; accepted 17 September 2007
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