How long do oysters stay fresh?

Ah, the age-old question: how long does something perishable last? We have all asked that at some point in our lives, especially in front of our fridge. Sometimes, it’s easy to figure out: a weird smell, visible mold – it’s probably time to throw it out. But what about perishable foods with less obvious signs, like oysters without “Best By” dates?

We have been conditioned to rely on dates to help us decide if something is still fresh or safe to eat, but what does “fresh” really mean for oysters? Have we assessed quality without a date bias? Our industry has become so focused on harvest dates and marketing that the oyster’s actual freshness is being overlooked.

From a food safety perspective, oysters stored at proper temperatures can be safe to eat for months. Oysters were historically stored in pits or cellars during winter and consumed during the winter months. “Pitting” or overwintering oysters in coolers and cellars is still a popular technique for growers to keep oysters safe from winter sea ice.

From a freshness perspective, we at Pangea Shellfish define oyster freshness as the following:

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A fresh oyster is alive, has ample liquor, and maintains its aroma and flavor from harvest.

Based on that definition, there are some signs when an oyster has gone bad:

  • The oyster is gaping open, which means it is weak or dead.

  • The oyster is dry, which means it is weak, injured or dying.

  • The oyster smells or tastes different from harvest.

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We have generally found oysters to maintain our definition of “freshness” for up to 14 days. Our observations, though, have been anecdotal, and we didn’t have concrete proof. So, for the month of May, we decided to put our assumptions to the test by shucking one oyster per day and tracking the changes over time.

A Month-Long Freshness Test

The Sample

For this test, we used a 100-count bag of Salten Rock Oysters from our Blish Point Oyster Farm in Barnstable, MA. We chose this oyster because we knew its seed to market process intimately. If something occurred during the test, we could potentially trace the issue back to the farm.

Procedure

We randomly selected 1 of 14 bags from Lot C-748. The lot was harvested on Saturday, April 27, picked up by our company truck, and received at our Boston facility at 4:40PM the same day. We stored the bag of oysters in a crate, on a shelf, and in our cooler for the entire test period. The cooler temperature averaged 41° F. The oysters received no special treatment. No special handling, no ice or special storage, and no wet storage.

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We evaluated one oyster per day. Before Bekah and I shucked each oyster, we recorded the oyster’s size in inches and weight in grams. Once open, we recorded its temp, captured a photo, and noted its liquor content and flavor. On the last day of the test, May 31, we shucked all the remaining oysters to see how they held up.

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Data & Results

Starting Bag Weight: 13.96 LB
Ending Bag Weight: 13.19 LB
Weight Change: -0.77 LB

Bag Yield: 96% (4 oysters dead or dry)
Size range: 3.0” - 4.0”
Average size: 3.6”

Figure 1: The following shows the weight of each oyster evaluated per day during the test.

one oyster weight was recorded each work day in May. 79 oyster weights were recorded on may 31.

one oyster weight was recorded each work day in May. 79 oyster weights were recorded on may 31.

Figure 2: The following shows the distribution of oyster weights shucked on May 31 (34 days post-harvest). The average weight of these oysters were 56.1 grams.

Most of the oyster weights ranged between 48 to 64 grams. Mean: 56.1 grams; Median: 55.2 grams; mode: 56.4 grams.

Most of the oyster weights ranged between 48 to 64 grams. Mean: 56.1 grams; Median: 55.2 grams; mode: 56.4 grams.

Figure 3: The following photos and notes were captured to assess meat, liquor, and flavor. Click on the photo for the oyster’s details.

Discussion of Results

Change in Overall Bag Weight

At the start of the test, the bag weighed 13.96 lb, and over the 34-day period, it lost 0.77 lb (349 g). If we average the weight loss across the bag, each oyster lost about 0.0077 lb (~3.5 g), about the weight of 2 playing cards. We expected this weight loss and it's within reason. Over time, moisture from the outer shells will evaporate and some oysters will weaken, losing some of its liquor in the process.

Change in Individual Oyster Weights

We hypothesized that the individual weight per oyster would decrease over time due to the expected moisture and liquor loss. What we found, however, was there was no direct correlation between time transpired and weight. In fact, oysters evaluated on May 31 (34 days post-harvest) ranged up to 80.9 grams, heavier than all oysters evaluated prior. Liquor was also visible in most of the oysters on the last day (see Figure 3).

This doesn’t mean that the oysters gained weight after harvest (that’d be highly improbable). Instead, this called out a flaw in our testing method. We were just as likely to draw 5 of the largest oysters or smallest oysters from the bag each week. Doing a more extensive test or having an oyster “control group” would make this more bulletproof. But hey, we’re oyster people, not scientists. One thing we can say is that the oysters we selected each day were of average weight compared to everything else in the bag (see Figure 1).

Change in Smell and Flavor

The oysters evaluated towards the start of our test easily met our definition of fresh: ample liquor, great meat fill, and flavor on point. The oysters continued to pass our standards for a few weeks with a couple exceptions (May 8 & 10). There were no significant changes until we reached May 17, 20 days post-harvest. From that point on, the smell and flavor started to turn. A couple of dead oysters started to make the bag stink. Oysters still had full meats and liquor, but they no longer tasted clean or pleasant. The funky lingering finish clearly was not representative of its merroir anymore.

Conclusions & Considerations

So what did we conclude or prove from this test?

1. Oysters are safe to eat even 30 days after its harvest date *if it has been handled and stored properly.

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Here is a photo of me eating one of the oysters on May 31, 34 days post-harvest. Happy to report I did not get sick and am alive and well to write this! (I also ate them during week 5 to assess flavor.) The caveat about handling and storage is super important to mention, though. The oysters were safe to eat because they were properly handled and stored at temp. This is a must to ensure safe consumption regardless of its harvest date. Mishandling is one of the greatest risks for foodborne illnesses caused by oysters, so please do your part.

2. An oyster can maintain its “freshness” or quality up to 14 days after harvest.**

From our test, oyster quality started to decline 20+ days after harvest. We generally tell customers oysters stay fresh up to 14 days, but our results showed the period of freshness may actually be longer. We like to err on the side of caution, so 14 days from harvest is probably a good rule of thumb to follow.

**This is a general conclusion and may not apply to all oysters. We recognize that different species of oysters have different shelf lives. Atlantic oysters (virginica) tend to keep better than Pacific oysters (gigas). Performing this test with Pacific oysters could have yielded a shorter freshness window. We used a farmed oyster versus a wild oyster. We used a Massachusetts oyster that feeds longer than a Canadian oyster. We acknowledge these differences in oyster characteristics can affect the outcome. This was also only one test done on a small scale. Perhaps we will repeat this again to compare our results, and maybe on another variety!

3. Freshness is not determined by dates, weights, or visual indicators. It’s all in the taste.

Before we embarked on this test, we thought we could assess quality by looking at an oyster and its numbers, i.e. its dates and weights. But what this experiment showed us is those characteristics can be deceiving. It doesn’t matter if an oyster is live, plump, and full of liquor. It doesn’t matter if an oyster was harvested 24 days ago. What matters most is if an oyster tastes good, and to determine that, you’re just going to have to eat it.

The Underappreciated Atlantic Surf Clam

Every summer at clam shacks in New England, the classic debate rises: fried clam strips or fried clam bellies? In my opinion, the two should not be compared. These sweet and salty fried treats are not even products from the same clam. The popular option is to use whole bellies, which come from the Eastern shores and are known as steamers, soft-shells, or piss clams. The less popular option, strips, are cut from a larger hard shell clam, the Atlantic surf clam. Both are an amazing sea treat, but I think the surf clam deserves some more attention.

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The Atlantic Surf Clam (Spisula solidissima) is a large, hard shell clam that is found in large numbers along the coast of the Northeast and primarily harvested in New England. They are triangle-shaped measuring on average six inches across at the time of optimal harvest. Their weight at this size is about two pounds making them one of the largest clams we eat. Most of these landings occur in the Nantucket Shoals where annual quotas remain around 3 million pounds. These landings are primarily used for processed products with very little sold as live product to the end consumer. Processed products include clam juice, clam strips, minced clams, and the belly (viscera) used for bait or industrial use.

 
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How surf clams are processed

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The first step in the production process is to remove the meat from the shell by hand. Lines of workers remove the meat by using short, blunt knives and make quick work of the difficult process. The juice released in this process is strained, packed, and frozen for use as a base in sauces and soups. Next, the meat is rinsed of any sand or grit, and a quick burst of heat removes any membranes or connective tissues that are not fit for consumption. The majority of the viscera, or belly, is removed and discarded, or saved for bait. The siphon, the mantle (or strap), the two adductors, and the foot are chopped and sold as minced clams. These pieces are usually about the size of a dime and stored back in their own juice in plastic containers. This product is used as a base for soups and chowders as well as an ingredient in items like stuffed clams and croquettes. The foot, if not used for minced, will be cut lengthwise and sold as the clam strip.

The emergence of the clam strip

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The clam strip is a relatively new way to use the surf clam. It was created for a business in the 1950s: Howard Johnson’s Restaurant. The famous orange and turquoise roadside respite was well known for their ice cream and quick and eat food, but the one thing they had people clamoring for was their fried clam plate. During that time, soft shell clams were increasingly scarce and the demand for fried clams was high. The restaurant’s source for clams was a company by the name of Saffron Brothers, a family business that started in the early 1940s by digging soft shell clams in Ipswich, MA. Not wanting to lose the business, the Saffron Brothers came up with the idea of using a clam that was readily available and less expensive to harvest. The brothers armed boats with hydraulic dredges, pulling up the large clams in droves. They processed them and sent them to the restaurant and were received with open arms. A new product was born and a New England staple emerged: Howard Johnson’s Tendersweet Clams. Soon, establishments up and down the Eastern Seaboard were using and frying the strips, hoping to capitalize off the acclaim. Since then, it has remained a staple in New England and enjoyed by many throughout the year.

Uses in fine dining

Photo Courtesy of Chef Brian Young of The Emory

Photo Courtesy of Chef Brian Young of The Emory

Surf clams can also be found on high-end sushi menus, commonly known as Giant Clam (Hokkigai). Often, the foot will be steamed, sliced lengthwise, and served on rice as nigiri. The tip of the foot will turn a bright pink or red, making it a standout among the tuna and salmon. Another way this clam can be used is in a raw preparation by using more than just the foot. By separating the parts of the clam normally used for minced clams, careful slicing can turn them into a high-end dish. The texture and flavor profile are similar to geoduck, yet mild and versatile enough for a large number of applications. Chef Brian Young of The Emory in Boston uses surf clams as a vessel for delicate and high-end ingredients. He thinks that all of the extra work to clean them is well worth it. On the right, you can see a dish that he created for a dinner at the James Beard house this past winter. The surf clam is sliced thinly and served raw with cultured cream, caviar, mizuna, and potato chips dusted with dried Italian truffles. This surf clam dish is certainly a whole other world from a fried clam basket or Striped Bass bait.

Curious about how to use these clams in your kitchen? Here’s a quick video on how to break them down and a recipe for a quick and easy dish inspired by spring.

#eatmoreclams

*As this piece was in production, an ordinance was put in place on April 9th, closing Nantucket Shoals for surf clam harvest until further notice. Since this is the largest area of harvest in the Northeast, it is hard to say exactly how the industry will change, but we are waiting on more updated information. Stay with us as we navigate this closure and find out more on the future of the East’s most underappreciated clam.