By Katharine Sucher, Staff Writer
When it comes to a new way to make seafood products safer, it’s nature versus nature.
Virginia Sea Grant (VASG)-funded researchers and extension have found a natural way to reduce risk of food borne illness from eating oysters.
The method, known as oyster relay, involves moving oysters to saltier waters before their final harvest. Oyster relay could prove to be a less expensive, yet natural, alternative to other currently available methods. This summer, researchers submitted data to the Virginia Department of Health (VDH), seeking to have oyster relay become an approved post-harvest process.
Kim Reece and Corinne Audemard of Virginia Institute of Marine Science (VIMS) and Mike Jahncke, VASG affiliated extension at Virginia Tech (VT), completed separate oyster relay studies with oyster growers in Virginia and Maryland. Both projects found that relaying oysters to high salinity waters about three to four weeks before sale led to significant reductions in levels of Vibrio vulnificus, a bacterium that causes food borne illness in people who eat raw or undercooked shellfish.
While post-harvest processing is not mandated in Virginia, oyster relay could help growers improve the marketability of oysters for both safety and taste. The only other validated post-harvest process in Virginia—freezing—kills the oysters, making them less desirable for half-shell eating; some consumers also notice a change in the quality of the oysters. Oyster relay, on the other hand, keeps oysters alive and may improve the flavor.
“Moving the oysters to higher salinity waters salts-up the oyster, so it’s a little more desirable for consumers,” Jahncke explains.
Approval of oyster relay, which would require both VDH and federal FDA signoffs, could also add flexibility for Virginian growers. Virginia is currently the only state to have just one validated post-harvest method, freezing. Three other processes have been approved in some other states. VDH and FDA approved freezing as a post-harvest process method for two Virginia companies in 2005—a result of research led by Jahncke and others at VT.
“If oyster relay was approved as a post-harvest process method it would mean that growers have another option for treating their oysters for safety,” Reece says.
The environmental aspect of offshore oyster relay, however, presents new challenges. Compared to an indoor, controlled method like freezing, Jahncke explains, “It’s a little more challenging when you take [the process] into the environment, because you’ve got other factors.”
The fact that oyster relay has not yet been validated in any other state also makes the validation process a bit trickier compared to other methods that now have off-the-shelf solutions, says Keith Skiles, director of the division of shellfish sanitation at VDH.
“If someone [in Virginia] wanted to validate high pressure processing and they bought a machine, that validation process would be a lot more straightforward because that technology has already been proven,” Skiles says. “This [oyster relay] proposal is a little different because it’s not a method that has ever been validated for reducing vibrio levels.”
Still, Skiles is optimistic about the future of oyster relay, saying, “The impression that I’ve had was the method will likely work pretty well for Vibrio vulnificus.” He adds that “It would probably help that we have data from multiple sources,” referring to the combination of research by Reece and Jahncke.
If VDH approves oyster relay, it will send the data to FDA for a second review process. But on the path to becoming a post-harvest process, it’s not only validation that matters. The industry’s reception of the process will also play a role in whether or not oyster relay will be used in the real world.
Initial responses from Eastern Shore growers, who work near high salinity waters, have been mostly positive. For Eastern Shore growers, having nearby, easy access to saltier waters to relay their oysters might be shaping that response.
“The concern for the western shore people has been the cost,” Reece says. For these growers, relay might require harvesting and packing their oysters on a truck to transport them to saltier waters. “Most of them think they probably couldn’t afford to do it unless there was some conglomerate or group that came together and paid for the shipping.”
Another alternative for these growers could be relaying oysters to high-salinity tanks. In addition to offshore studies, Jahncke also conducted successful in-tank relay studies. Finding options for growers throughout Virginia is important, says Jahncke.
“Our work here is about working with the seafood industry in general. We try to help all companies produce a safer, more high quality product.”
