There's always been this oft-recited piece of advice about oysters: Only eat oysters in months that contain the letter "R" in the name. You know, September, October, December, January. Not June, July, August.
But if this is true, how do millions of restaurants sell them year-round to people who seem just fine after eating them? If we've been eating oysters all summer, have we been putting our health at risk? I put the question to two oyster experts: Chris Sherman at Island Creek Oysters and Rowan Jacobsen, author of A Geography of Oysters. Here's what they had to say.
After a nasty encounter with food-borne illness from eating one of those gorgeous, multi-tiered shellfish platters at a Parisian brasserie, it took me a long time to work up the nerve to eat raw shellfish again. Even though I'm back on the half-shell bandwagon, I'm more cautious now; I decided it would be in my best interest to arm myself with some more knowledge, especially about raw oysters.
The Original Advice
The original advice is that you should only eat oysters in the eight months of the year that contain the letter "R" in the name, which means September through April. The other four months of the year — May through August — are off limits.
Why the restrictions? This advice was actually wise when oysters were harvested from the wild rather than farmed. Jacobsen says, "Oysters spawn in summer, when water temps are at their warmest. Traditionally, the season was closed on them during much of the R-less months (May through August) so they could reproduce, and also because in preparation for spawning, they convert glycogen stores to gamete (sperm and eggs). They get soft and rank. And last, pre-refrigeration, it wasn't safe to eat a raw animal that had been baking on the docks in wooden barrels all day long."
Besides the warmer temperatures resulting in more food safety issues, Sherman echoes that due to the life cycle of the oyster, they're just not as tasty in the summer since you will end up with a "flimsy oyster if you get it right after it spawns."
The other factor behind this advice was higher red tide levels in the summer, which happens when there are higher concentrations of an algae that is toxic to humans. Eating shellfish that absorb this toxin could lead to PSP (paralytic shellfish poisoning). Bacteria is also more prevalent in warmer waters.
Do We Still Need to Follow This Old Advice?
Modern-day oyster farming and strict environmental rules and enforcement have changed the landscape of oyster eating so it's now safe to eat oysters year-round. Here's why:
1. Many oyster farms are in cold waters
Colder waters can produce edible oysters year-round. Sherman says, "90 percent of oysters from the Northeast are farmed in areas where they don't spawn or have a quick spawn (may be too cold)."
2. Different oyster breeds
Oyster breeding also has a lot to do with the oysters you can eat in the summer. Jacobsen says, "Many oysters from warmer regions are now triploids, which are bred to be sterile (the same way that seedless cukes and watermelons are bred to be sterile — they're also triploids). They never reproduce, so they don't get spawny in summer."
3. More monitoring and accountability
Oysters are also safe to eat year-round because there is more monitoring and accountability to protect consumers. Sherman says there is sophisticated monitoring of every step of the farming and harvesting process, including water-quality monitoring for bacteria and pollution. At Island Creek, they make sure they are testing and following guidelines every step of the way. Only oysters from clean waters will make it to consumers.
If there are high concentrations of toxic algae detected, harvesting is banned during that time. The U.S. is so strict about oyster safety, oysters cannot be imported from the European Union because their guidelines are not as strict.
4. Better food safety practices
There are also stricter and better food safety practices when it comes to handling oysters. Jacbosen says, "Oysters have to be refrigerated the moment they come out of the water, and stored at that temperature all the way to your plate, so safety is less of an issue." Sherman adds that the "whole industry has more knowledge and awareness of handling," and he also says they invest in infrastructure like ice machines, refrigeration, and other new equipment.
The Best Times of Year to Eat Oysters
Now we know it's safe to buy and eat oysters year-round, but are there times of year when they taste better? Jacobsen says, "Most oysters still taste much better in fall and winter than they do in summer. Oysters taste best out of cold water, so I say to follow the frost line — southern oysters in late winter and early spring, northern oysters in fall, and everybody around the holidays."
Sherman says there are "huge seasonal differences in the flavor of the oyster, like vintages of wine. Island Creek oysters in summer are totally different than in November or February." His favorite time of year is in September and October, when the oysters are really "plump and sweet."
Best Practices for Eating Raw Oysters
When you're buying raw oysters, here are some best practices for buying and storing oysters.
- Buy them from reputable sources. Trust who you're buying them from, and make sure they look clean and are stored properly, like on ice.
- Look at labels. By law, oysters need to be labeled with where they came from and harvest dates. Don't be afraid to ask!
- Buy heavy oysters. Jacobsen says, "They should be heavy for their size, just like fruit. If they feel light or sound hollow when you rap them, don't buy them."
- Store them properly. Sherman says to put raw, unshucked oysters in a bowl in the refrigerator. Cover them with a damp dish cloth so they don't dry out. They don't have to sit on ice, but make sure the refrigerator temperature is around 38 or 39°F. C.J. Husk of Island Creek says, "'R' stands for refrigeration these days."
- Don't wait. Eat oysters within a week of harvest in the summer, and within 10 days in the winter.
- No mud. If you see mud in the shell after you shuck an oyster, pitch it.
- Don't spill the liquid. You want the juices or "liquor" of the oyster to stay in the shell until you eat it, so after shucking oysters, place them on plates in a way that the shell doesn't tip and spill any of the liquid out. Place oysters on the half shell on plates lined with ice or coarse salt so they stay put.