Fish – Mackerel brining time before smoking

Theory is a good thing, but data is always better. Especially when somebody else does the whole work of gathering and evaluating it. Luckily, there is somebody who does it for food. Following data comes from the USDA. It is very verbose, so I had to cut off most of the screenshots. I left all the lipids in the first one just to show how much they measured, and only used the data for Omega 3 in the other ones.

The first data set is raw Atlantic mackarel. I picked Atlantic just because it was first in the list, they have several kinds.

Sadly, they didn't have data for smoked mackerel. But as Frankie points out, you can do a hot smoking process and a cold smoking process. I think that the cooking in both is very well approximated by cooking on dry heat, resp. salting. Of course, it is possible that the smoke itself destroys more fatty acids than just applying heat or brine, but these numbers give us an upper limit for the amount of omega 3 left after smoking.

Now we can start making conclusions.

First conclusion: there is something fishy about the data.

Zero standard deviation for all the values in the raw fish? Zero data points for the salted fish?! I can only assume that they just wrote a zero where the actual information is missing from the record. Still, I think we can trust the data (because the USDA has no interest to lie and because we don't have a better data set).

Before we start making further conclusions, we should remember that these are values per 100 gram of end product. 100 g of salted mackerel isn't made with 100 g of raw mackerel! Luckily, the source also gives the water percentage of the samples (not shown on the screenshots), which is 43% for salted mackerel, 53% for cooked mackerel and 63% for raw mackerel. So, we should in fact compare the numbers per 100 g of dry matter (we assume that the cooking process neither adds nor subtracts dry matter - not exactly true for salting, but we can assume that the difference is small). The numbers are:

Second conclusion: Heat (so presumably also hot smoking) destroys around 40% of the fatty acids in mackerel

This is straightforward, comes from the numbers in the table.

Third conclusion: The salted mackerel didn't come from the Atlantic

Unless I have made a big mistake in my reasoning about the comparison based on dry matter, a salted fish has more omega 3 than a raw fish of the same size. The difference in data is small enough to have been caused by the choice of a different kind of fish (note that the standard deviation within a sample of the same kind of fish is 10 to 15%).

Fourth conclusion: Cold smoking probably doesn't destroy a significant amount of omega 3 acids.

While the data comparison here has some problems (the assumed different kinds of fish, the fact that salting isn't the same as smoking), I think we can see the trend here. If the salted fish had lost too much of its omega 3 in the salting process, then it wouldn't have such high omega 3 values after the salting. We can assume that a cold smoked fish is also salted (my personal experience and Frankie's answer support that), so any possible preserving effect of salt should be present in cold smoking too. There is a risk that the smoke itself could destroy the fatty acids, but I doubt it. After all, the smoke doesn't penetrate the tissues very deep, so there shouldn't be much contact.

Of course, I am not 100% sure about the conclusions above, but I think it is reasonable to assume that they are true. I have tried to make clear any possible problems. So the short answer is: fresh mackerel and cold smoked mackerel have about the same amount of omega 3 fatty acids, but hot smoked mackerel has much less omega 3 than the original.

I suspect that the biggest problem here is that your brine isn't anywhere close to being strong enough. Cooks Illustrated has a good guide to the entire process but in a nutshell:

• Sea salt is expensive and inefficient for brining; the impurities actually make it more difficult to dissolve and disperse properly. Kosher salt is generally recommended, although table salt is also fine.

• A typical brine is 1/4 cup table salt and 1/2 cup sugar per quart, which translates to about 70 g and 140 g respectively per L. For very high-heat methods (grilling/broiling), you halve the amounts. Also, for kosher salt you need to double the volume (no change if measuring by weight). Even the lower, high-heat cooking concentration is almost twice as concentrated as what you're doing.

• You also need to scale the amount of brine with the weight of the bird itself. The rule of thumb is 1 quart or L per pound (2.2 kg) of meat. For a whole chicken, which is generally around 6 or 7 pounds, 1.5 L of brine is nowhere near enough, especially if you're brining in a pot as opposed to a bag (does your 1.5 L even cover the chicken?).

• It doesn't really matter if you butcher the chicken first (although most people don't). You're exposing slightly more surface area that way but not really enough to matter.

• Make sure you are actually dissolving all the crystals! From what you're describing, you're getting high concentrations of salt in some areas and none in others. That means you didn't get proper dispersion. You really need to make sure that all of the salt (and sugar, if you're using any) is completely dissolved, otherwise you don't have a "brine", you have water with a bunch of little piles of salt. Some people will suggest heating or even boiling your brine to ensure proper dissolution; just make sure you let it cool off afterward if you do this, before submerging the bird.

In answer to your specific questions:

1. The container should be well-sealed to prevent evaporation, not to mention off-odours in your fridge. However, I've used pots with loose-fitting lids and had no problems. It doesn't make a huge difference as far as the efficacy of the brine.

2. Fridge temperature is ideal. Do not even think about using room-temperature water, that is highly unsafe for storing raw meat for 6-8 hours at a time.

3. As long as you don't overcrowd the vessel and do disperse the crystals properly, the actual amount of space is not a major issue. If it's exposed, it's exposed.

4. Longer than 12 hours is not recommended. Actually, according to CI, longer than 8 hours is not recommended. Don't overdo it - you're brining, not marinating.

5. No matter how you cook any piece of meat, it will give up a certain amount of water and therefore a certain amount of salt (from the brine). Left unstated is why you would even consider boiling a brined chicken; brining is primarily a technique for dry-heat cooking (roasting/grilling), and if you want to boil/poach/braise/whatever then you should be focusing more on flavouring the cooking liquid than the meat itself. I wouldn't bother brining if you're making chicken soup, there are better ways to flavour that.