What makes oysters fresh?

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There are real sensory and handling differences between an oyster harvested and consumed straight from the water versus one harvested 7–14 days ago, even if both are perfectly safe to eat.

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This post explores the following factors and what makes a fresh and satisfying oyster:

• Taste and culinary quality

• Food safety factors

• Post-harvest handling

Most oyster fans collapse all three of these factors into a single word: “fresh.” But these factors play a nuanced role. What one might find surprising about oysters, is that a little “resting time” can actually improve the taste experience.

Why consumers equate “fresh” with “better”

Seafood consumers generally assume:

• shorter time from harvest = higher quality

• more ocean flavor

• safer product

These assumptions are not irrational as deterioration of most seafood does start immediately after harvest. This is why Tuna species are flash-frozen for the lucrative sushi market.

But when it comes to oysters, spoiling does not occur as fast as you might think. And because we have been conditioned that fin-fish seafood freshness is directly attributed to a very short time from harvest to consumption, most seafood receives a similar judgment.

Research from Auburn University shows oysters gradually change during storage due to:

• enzyme activity

• microbial growth

• loss of glycogen

• changes in volatile compounds and liquor chemistry (AUETD)

Note: that the same university pioneered oyster harvest best practice research.

But properly handled, live oysters do not deteriorate like fin-fish. First of all, one must realize that oysters are considered "live seafood" because they are still alive when they are pulled from the water. And if properly handled and kept at the proper temperature, oysters can be safely returned to the water up to several weeks where they will sense emersion, open, and start to breath and feed again.

During this out of water experience oysters are using sugars and fat to remain alive, but it does not take much. Oysters out of water and kept around 40 degrees puts them in a slow-metabolic state, similar to hibernation. This natural ability is exercised 2X every 24-hour period for several hours in the littoral zone when the tide recedes and exposes oysters to the air. This is how oysters can remain viable for weeks following harvest because shutting down and going dormant is like second nature to them.

Virginia has a restaurant-specific food-safety rule for oysters: Restaurants can serve oysters up to 14-days from the harvest date. This rule is all about risk management.

As we have shared in other posts, all oysters are required to have a traceability tag attached to them and any competent oyster server should know the basics on when and where oysters were harvested.

Virginia’s conservative time limits are primarily driven by:

• food safety & approved harvest zones

• temperature abuse concerns

• Vibrio bacteria risk (see Hot Topic)

• traceability/regulatory simplicity

Not because on day 15 oysters suddenly become bad.

Under ideal refrigeration and humidity:

• many oysters remain alive and safe well beyond 14 days

• industry anecdotes commonly cite 21–30+ days for premium handling (See this Reddit post)

So are ultra-fresh oysters straight from the water always better? This is where it gets interesting. Not necessarily.

Anyone who has shucked an oyster straight from the water knows that the animal is on high alert and literally fights back against knife work. Contrast this same animal that has been snoozing in a cold state for days, and the shuck is a sneak attack not possible with oysters straight from the water.

Many experienced shuckers and oyster people quietly acknowledge that oysters often benefit form a short stabilization/resting period after harvest before serving. The advantages of a few days of cold storage provides easier shucking. Why?

• adductor muscles relax slightly

• internal pressure changes

• less shell breakage

This effect is well known commercially, and research on HPP oysters even measures improved “shucking yield” following cold storage. (MDPI) see right

In November 2023, LOC Members were able to enjoy oysters straight from the water. This rare opportunity is just one of the benefits of long-term membership with LOC.

Don't get us wrong, a fresh from the water experience is special and unique, despite the greater shucking challenge, but one day at VDH-regulation temperature might as well be seven when it comes to oysters.

Serving straight from the water is also impractical for many. Only one event in our 5-year history (Fire & Ice) was able to provide an ideal straight from the water experience.

A few days of proper cold holding is somewhat analogous to:

• resting beef

• conditioning cheese

• cellaring wine

The rubber bands holding these oysters together in the mesh bag are a sign that these oysters were opened using High Pressure Processing. HPP (typically 30–45K PSI) is a cold-pasteurization technique that completely separates shellfish meat from their shells. The downside of HPP? As the oysters are opened under water under extreme pressure, all of the liquor that makes the oyster unique gets expunged in the HPP process thus changing the taste profile from the pre-HPP opened original.

A wide variety of experienced opinions exist on this topic: (Check out this Reddit post)

One of the biggest sensory indicators of freshness is not actually the oyster - it is the retention of liquor. As oysters age, liquor can slowly leak (see our FAQ on storage) which contributes to muscle tissues dehydrating. This changes the eating experience dramatically which is why we favor boxing our oysters and packing them carefully cup side down. (Put link to article once posted here). The liquor carries:

• salinity

• aroma compounds

• minerality

• sweetness perception

Also, cleanliness matters. While well-hydrated oysters inside their shells are nice and cozy, any organisms on the outside of the shell that were not cleaned off after harvest and prior to storage can spoil with age. This is where your nose might confuse the actual suitability of an oyster inside the shell with an overall aroma that screams "do not eat!". Once you nose has detected something like this, it is hard to move past it, even if the oyster is not spoiled.

To recap, so what does "fresh" really mean?

For oysters, “fresh” is less about "harvested this morning" and more about:

• continuous cold chain

• storage orientation

• retained liquor

• clean oysters cut down on aroma

From a taste experience, a well-handled 10-day oyster may easily outperform a poorly handled 2-day oyster.

In closing, "fresh" oysters are not simply the ones eaten closest to harvest. The best oysters are those have have been properly handled, kept continuously cold, alive and served within their optimal sensory window. There is credible culinary evidence that a short resting/conditioning period after harvest can improve shuck-ability and sometimes flavor balance. 🦪