Admit it: you’ve got great taste. (Exhibit A? You’re a fan of Vital Choice!) Which is why it should come as no surprise to you that of all the highly technical terms used by industry insiders in the world of fish freshness, the number one expert on freshness is you - you and your nose, that is.

That matters, because freshness isn’t just a matter of taste, it’s a measurable marker of food safety. Delving into the depths of your refrigerator can tempt fate, depending on the staunchness of your stomach. That extra layer of fuzz on the long-forgotten gorgonzola may be fine, but fuzzy meat? Forget it.

So in the world of fish and its aroma, what indicates this particular deep-sea denizen is fresh – or not-so-fresh? To answer that, we need to better understand the fabulous fats that fish are known for.

The fats of life

Time for a science experiment! Grab the butter from your kitchen countertop. Stick it in the fridge. Very shortly, it will harden. Stick it in the freezer, and you’ve got yourself a (delicious!) brick.

Fish oil with flax grain and fish on wooden cutting board
Nature’s anti-freeze: Quality cod liver oil remains liquid down to minus 112 Fahrenheit.

Now do the same thing with the bottle of liquid cod liver oil that you’re undoubtedly taking for immune support. The cod liver oil won’t freeze - unless your freezer happens to go down below -80 degrees Celsius (Dawson, 2018).

So, bad news if you crave a cod liver oil popsicle, but good news if you’re a cod! (Well, at least if you’re a cod still in possession of its liver.) And good news for all fish that reside in frigid ocean temperatures: the omega-3s so plentiful in fish fat mean that these cold-blooded creatures can stay flexible and keep on swimming, even at sub-freezing temperatures.

Chain, Chain, Chain - Chain Of Fats

The reason your butter turns into a brick in the freezer is the same reason that you can leave your butter on your countertop without melting - it’s due to the predominance of saturated fats which give it stability. (And saturated fats as part of a balanced diet are not necessarily unhealthy, despite a long campaign against them by some mainstream health authorities.)

Lipids, or fats, are made up of different microscopic chains, and the structure, or shapes, of these chains will determine how they behave, move, signal, and flex - in our bodies, the cell membranes where they are stored will be accordingly flexible or rigid, depending on your dietary intake and the functional needs of a given type of cell.

The more unsaturated the chains are, the more double molecular bonds they have, which kinks the chains (rather like a spring is a kinked wire) and confers greater fluidity where they accumulate.

And the most unsaturated fatty acid chains are omega-3 EPA and DHA, predominantly found in oily, cold water fish. This is why fish oil can be stored in the refrigerator and even the freezer and not harden or solidify - unlike butter, which will harden into a butter-brick when frozen.

Packed to the gills…with fabulous fat

The reason fish don’t freeze solid in the ocean is due to the unique structure of omega-3 EPA and DHA - these essential fats confer fluidity and flexibility to the cell membranes in which they accumulate (Guitierrez, 2019).

Green violetear hummingbird hovering with wings open
The blinding speed of a hummingbird’s wings is due in part to the omega-3 fatty acids in its musculature – they allow for rapid, efficient motion.

This flexibility is essential for conferring muscular speed - it’s why EPA and DHA are found not only in fish oil, but in any place in nature which requires speed of movement: fast-twitch muscles like a rattlesnake’s tail, heart tissue, or a hummingbird’s wing, to name just a few (Infante, 2001).

And while every human organ requires omega-3 DHA, it is the predominant structural fatty acid in the central nervous system, retina, and the brain (Singh, 2005), which is why it’s played such a crucial role in human brain development.

Aroma wasn’t built in a day

While fish have a significant amount of fat present in their tissue, the deterioration of these oxidation-prone fats is not exclusively responsible for the “fishy” smell associated with seafoods.

Fish produce a specific amino acid known as trimethylamine N-oxide (TMAO) to maintain the balance of electrolytes and minerals in their cells, in order to survive the salinity of the sea water (Valesquez, 2016). This converts into trimethylamine (TMA) - which is the source of the fishy odor.

The freshest fish – such as the kind Vital Choice sources, which is rapidly chilled or frozen shortly after it is caught – has virtually no odor upon thawing. But as any raw fish is left in warm air, it begins to harbor bacterial and enzymatic activity, and a characteristic scent will develop and strengthen (Mei, 2019).

(“Fishy” odor is not the exclusive purview of fish, and even occurs in living humans, as evidenced by the unfortunate disorder of trimethylaminuria - also known as “fish odor syndrome,” in which bodily fluids produce the same aroma as that of decaying fish. Mercifully, this disorder can be managed with some dietary guidance [Messenger, 2013].)

The release of TMAO can promote bacterial growth in a wide temperature range, which is why the immediate refrigeration or flash freezing process is so integral for maintaining the utmost in fresh fish flavor (Mei, 2019).

But what if you like things a little… stinky?

We want the funk

Some pungent or complex odors seem distasteful to nearly everyone. Many food aversions exist as a survival instinct - our human ancestors learned the hard way that certain foods, whether a peculiar looking mushroom, a temptingly radiant red berry, or a not-so-fresh animal protein, can have devastating consequences; “unpleasant odors often signal danger, such as spoiled food or a toxin” (Boesveldt, 2010).

But without a doubt, our tastebuds and nostrils are also influenced by our culture and upbringing. Many traditional cuisines have a history of fermenting fish, fish sauce being a notable example still present in modern day cuisine.

Perhaps an acquired taste for modern foodies, most fermented fish dishes have undergone a preservation process that leaps over the hurdle of “gone bad” into “gone good”, once beneficial bacteria have been given significant time to work their magic and overcome pathogens (usually, at least 6 months).

But generally speaking, when it comes to fish, the fresher, the better - better to rely on the impeccable standards of freshness of fish cooled or flash-frozen in ultra-low temperatures within minutes or hours after catch, as sourced by Vital Choice.

Trust your nose – it knows!



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Gutiérrez, S., Svahn, S. L., & Johansson, M. E. (2019). Effects of Omega-3 Fatty Acids on Immune Cells. International journal of molecular sciences, 20(20), 5028.

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Messenger, J., Clark, S., Massick, S., & Bechtel, M. (2013). A review of trimethylaminuria: (fish odor syndrome). The Journal of clinical and aesthetic dermatology, 6(11), 45–48.

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Velasquez, M. T., Ramezani, A., Manal, A., & Raj, D. S. (2016). Trimethylamine N-Oxide: The Good, the Bad and the Unknown. Toxins, 8(11), 326.