Atlantic Salmon - and "cooking" it without cooking

 Who said cooking has to involve heat?

This week I looked into the process of curing salmon using an easy home-made Nordic dish called Gravlax ("Grav-locks"). Only salt, sugar, herbs, and time are used to cook the salmon. With no heat used whatsoever, the natural texture of the salmon remains incredibly intact. Imagine lox or sashimi, but instead of a Jewish deli or Japanese sushi house you're in a Norwegian fishing village. And for skeptics of how you can "cook" using only sugar and salt and some herbs, I'll dig into some of the chemistry behind the alchemy of curing. What's more, the recipe I'll share for Gravlax is laughably easy and insanely delicious.

This one hits close to home; it's one of my all-time favourite meals. ​Check out the recipe here, or read more below

Salmon - Atlantic for the win

Atlantic salmon makes the best gravlax due its high fat content. I've prepared it before using other varieties like Coho and King salmon - wild, leaner West Coast cousins of the Atlantic - and it just isn't the same. I'll explain the science of why more fat equals more flavour later. But for now it's safe to say you should use Atlantic salmon simply because the original Nordic gravlax was made using Atlantic salmon.

The cut you want from the fish shop is a 3/4- to 1-pound fillet of fresh Atlantic salmon, cut from either the front or back half of the salmon. Or, if you want to fillet it yourself, ask for a whole half salmon, weighing approximately 2 pounds (cleaned, head and tail removed). 
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Curing - lessons from history

Hammerfest, Norway in the middles ages. Norse fisherman have returned from the fishing grounds. They salt some salmon and bury it in the rocks above the high-tide line. Days pass; a pungent aroma drifts landward as it begins to ferment. Later it is brushed off and thinly sliced, consumed on thick wedges of dark rye bread. 

Slightly romanticized? Maybe, but that probably isn't too far off the mark. "Gravlax" literally translates into "dug salmon" - and while it's no longer prepared using fermentation, it is still cooked "raw," using only salt and sugar to cook it. It's not buried on the beach any longer, either; it's simply wrapped in plastic wrap and put in the fridge for anywhere between 1 to 4 days. The curing process that cooks the fish is called osmosis, a natural phenomenon similar to brining that happens when moisture moves from a low concentration to that of a higher concentration through a membrane. In other words, when the salmon is coated in salt and sugar and herbs, moisture flows out of the fish (the less concentrated fluid) and dissolves the salt, sugar, herb mixture to form a brine (the more concentrated fluid).  Some of the moisture lost from within the fish is then replaced by brine and the process is reversed: the briney mixture starts to concentrate and draw moisture back into the fish. This is where the "cooking" happens, since the brine dissolves some of the fibrous proteins (not to mention bringing the delicious brine flavours directly into the fish). The role of the sugar in the brine is mainly to balance the salty flavour and the extent to which the osmosis process is allowed to occur. A sweeter brine results in a sweeter, fleshier cured fish; saltier brine results is a saltier, tougher cured fish (image salt cod). ​

I mentioned before that Atlantic salmon makes the best gravlax due to its higher fat content This is because flavour-carrying brine dissolves in the fat within the fish, contributing greatly to the overall flavour of the curing salmon.

Adding pressure helps to draw moisture out of the fish and speed up the osmosis process, so it's common to add weight to the top of the fish as it cures in the fridge. A few cans of tomatoes will do. The curing will be ready in 24 hours but the flavours will reach their peak in about 3 or 4 days. 
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Serving - rye and lemon wedges

Gravlax is best served for brunch or as an appetizer. It's tradition to serve it on thin slices of dark rye bread, buttered, with a dollop of mustard sauce on top. See the recipe for how to easily make gravlax at home and suggestions for toppings, sides, and drink pairings.
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