ABCs of smoked salmon

Smoked salmon has never been so popular and affordable. Canadian consumers now have access to an ever-growing number of artisanal products from Canada and Europe. As with any perishable food, some precautions are required when used. Let’s take a peek at the world of smoked salmon.

A quick look at how it’s made

Salmon and other smoked fish, such as trout and sturgeon, pass through three consecutive stages. The length of each process, as well as certain variations specific to each manufacturer, produces differences in the fish’s taste, appearance and texture. The three steps are:

1) Salting. It is done either by dry coating or by immersing in liquid brine. This step reduces the moisture content of the fish and infuses it with salt to help preserve it.

2) Drying. The length of this step varies and aims to further reduce the moisture content. It also determines how the fish will absorb the smoke.  

3) Smoking. The fish gains its final flavour during this step, depending on the type of wood used and the length of smoke exposure. Salmon can be smoked hot or cold depending on the temperature of the smoker.

Three types of smoked salmon

Salmon can be smoked three different ways. The flavour and texture will vary according to the selected method.

Cold-smoked: Cold-smoked salmon is a raw product. The temperature of the smoker does not exceed 30 °C during smoking. The flesh retains its raw appearance and the texture remains soft, moist and chewy. This type of smoked fish is very perishable and should be kept in the freezer* prior to use.

Hot-smoked: To produce this type of smoked salmon, the smoker has to reach a temperature hot enough to coagulate fish protein. The appearance changes and flesh becomes firm and opaque, like that of a cooked fish. Hot-smoked salmon is usually sold refrigerated. As with any perishable product, it has an expiry date that must be respected.

Smoked and sterilized: After smoking, this type of salmon is packaged and sterilized, sort of like a can of food, by a heat treatment that destroys all bacteria. It can be stored in the pantry, as long as it has not been opened.  Its flesh is very firm and opaque, like that of well cooked fish.

Some precautions to take

Cold-smoked salmon is trickier than you think. Since it does not undergo heat treatment (a step that destroys bacteria harmful to health) and is usually consumed raw, it needs to be handled with care. Here are two golden rules to follow.

1. Pierce the packaging when thawing

More and more manufacturers indicate you should pierce the packaging when thawing in the fridge. Why? This is a precautionary measure against Clostridium botulinum bacterium, which causes botulism.

Understand that these bacteria only develop in the absence of oxygen (in vacuum-sealed packages) in low-acid foods that contain little salt and no nitrates (such as smoked fish). While salting and smoking helps preserve it a bit, the combination of these two processes is not enough to stop these dangerous bacteria.

In addition, the type of Clostridium (type E) that contaminates fish develops slowly but surely, even at a normal refrigerated temperature. This is why cold-smoked salmon is vacuum-packed and almost always sold frozen*: freezing protects against the development of these bacteria.

When the fish is thawed slowly in the fridge (over a period of several days), it is possible for this bacterium to develop and secrete a toxin that causes botulism. This is why it is recommended to pierce the packaging: the bacterium, or more precisely its spores, will not develop in the presence of oxygen. But rest assured that this is a precautionary measure! There has never been a case of botulism reported in Canada due to eating store bought cold-smoked trout or salmon. Note that it is not necessary to pierce the packaging if the fish is thawed quickly in cold water.

2. Use up leftovers quickly

Cold-smoked salmon leftovers should be refrigerated and eaten within three or four days after being thawed. Harmful bacteria called Listeria monocytogenes can develop if it is stored too long. These bacteria can cause listeriosis, a rare infection, but one that is particularly dangerous for pregnant women, the elderly and those with a weakened immune system. It is recommended that these individuals avoid consuming cold-smoked salmon unless it is cooked. Cooking destroys the bacteria. 

*Using certain breathable packaging and higher concentrations of salt allows cold-smoked fish to be sold refrigerated for up to 14 days.

And gravlax?

Salmon gravlax is raw salmon that is dry cured in a mixture of sugar, salt, herbs (typically dill) and spices, without being smoked afterwards. It has the same moist and chewy texture as cold-smoked salmon, but without the smoky flavour. A real treat! As with cold-smoked salmon, leftovers should be kept in the fridge and used up quickly.

Christina Blais

For Christina Blais, explaining food chemistry to the masses is as simple as making a good omelet. Holding a Bachelor and Master degree in Nutrition, she has been a part-time lecturer for over 30 years in the Department of Nutrition at the Université de Montréal, where she teaches food science courses. She has been sharing the fruits of her experience with Ricardo since 2001, during his daily show broadcast on ICI Radio-Canada Télé. And diehards can also read her Food Chemistry on our website. You can follow her on Facebook at @Encuisineavecchristinablais.