Toxigenic vibrio baselines and optimum storage, transport and shelf-life conditions to inform cold supply chains in the north Australian Tropical Rock Oyster industry
Charles Darwin University (CDU)
Karen S. Gibb
Internationally, Tropical Rock Oysters have a poor safety reputation with Vibrio at the top of the list. While a pro-active not reactive approach to vibrio food safety is essential for product assurance and branding, effort needs to be proportional to risk. And risk assessment also needs to be informed by real data. There are certainly knowledge gaps for north Australia, but we know seawater contains up to 42 Vibrio spp. including several known toxigenic species in addition to the human pathogens Vibrio parahaemolyticus (Vp) and V. vulnificus (Vv). We know Vp responds to temperature but Vv does not. And we know Vv concentrations in seawater are higher in the wet season compared to the dry, and more shellfish are Vp and Vv positive in the wet season. So if vibrio diversity and abundance in TRO is seasonal (as shown elsewhere), it is likely that Vibrio spp. infections in humans will also follow a seasonal trend which has implications for risk management. A major bottleneck is that we don’t know how vibrios respond to storage and transport temperatures in TRO. We know that the Pacific and Sydney Rocks respond differently so it is not ‘one size fits all’ and it is certain TROs will be different again. In addition to identifying vibrio baselines in TRO and developing tests for toxigenic species, we will identify the best post-harvest storage and transport temperatures and assess TRO shelf life at realistic storage temperatures. This will provide fundamental information to inform cold supply chains that will support farmers, wholesalers and retailers of TROs from north Australia. We can also use this information to prepare an appropriate and regionally relevant vibrio risk profile for TRO in northern Australia to assist initial risk management activities. This information will provide the developing TRO industry with the knowledge needed to ensure an exemplary reputation, thus giving access to premium markets.
1. Measure vibrio baseline in Tropical Rock Oysters and develop tests to vibrio species that are toxigenic to oysters and humans
2. Identify optimum storage and transport temperatures to inform post-harvest cold supply chains
3. Assess TRO shelf life at realistic storage temperatures to maximise product quality and inform cold supply chains
4. Use objective 1-3 outcomes to produce a risk profile for vibrio in north Australian TRO that will support the industry as it seeks to deliver a safe, premium product