Posted some of this here already but thought I'd run the both versions of the recipe in this thread. Will make it easier to find next winter...
There are basically two versions, one which incorporates sugar in the wet brine, and one which doesn't.
I'll post them both for any who wish to try.
That said, after the last experiment, I am leaning towards the recipe that does include it...
Cold Smoked Tuna
Slowly thaw the desired amount of whole tuna loins. Once thawed, make up a DRY Brine of 2 parts Demerara Sugar to 1 part non-iodine (coarse or pickling) Salt. Put enough of this in a plastic container to cover the bottom of it.
Place the tuna loins on top of that. And cover well with the balance of the brine mix.
Now let sit for at least 24 hours in the fridge (If you don't have room in your fridge, keep cool by whatever means). After that period the tuna will have "leaked" a fair amount of juice (moisture) and the brine will pretty much dissolve.
At this point the tuna will have darkened substantially in response to the dry brining process.
It is not necessary to rinse the loins, as they now go onto the next stage - the Wet Brine process. Yes, that is correct, two brines as apposed to a single one that we are all most familiar with. I chose to go this route due to the advice of some VERY serious lox producers who insisted this was the "preferred" method to ensure a great quality product.
Salt Saturated Wet Brine
Run enough cold water into your tub to cover the tuna. Add in a LOT of salt (in this case a little better than half a bag went into the brine). You want a "super saturated" solution, meaning that the brine can absorb no further salt, and there is salt settled out on the bottom of the container. Drop a raw egg into the brine to test. If it floats, good to go. If not add another 1/2 cup of salt and try again.
Then add the tuna loins. Let sit in the fridge or a cool place for another 24 hour minimum period.
Following that the loins will lighten considerably.
Remove from the brine, and prepare for the next step
Alternative Salt & Sugar Wet Brine
Run sufficient water into your brine tub to well cover the tuna. Add in Demerara Sugar at 2 parts to one part Coarse Salt, then add just a hint more salt. Conduct the egg test to ensure saturation levels. Toss in the loins & keep cold while it sits for the next 24 hours.
Remove from brine and ready for Freshening.
Freshening or Desalination Process
This next step is CRITICAL and very finicky!
This is termed "Freshening" in which the salt is slowly removed from the tuna.
Place the loins in another container and run cold water into that, allowing the water to run over the sides carrying away the salt with it:
You MUST keep a VERY sharp eye on this process! If you don't allow sufficient time for the desalination to occur, the tuna will be overly salty, and no-one will want to consume it! On the other hand should you leave the loins in for too long, they will turn into a wet soggy mess and be ruined - non-recoverable error!
Check the tuna over the freshening period. What you want to see is the ability to slice the loin VERY thinly, and little to no salt taste.
Once done to your satisfaction, drain the water and ready for the next stage.
Drying & Glazing
The Glaze is a mix of full bodied Black Rum, maple syrup and brown (Demerara again) sugar. I used quite a large amount of rum, as I like the taste it instills. For this run the ratios were 3 Parts Rum to 1 part Maple Syrup. Then I added in 1/2 bag of the sugar. The sugar will settle out, so to combat that and mix it well, heat (GENTLY) just until the sugar dissolves. DO NOT OVERHEAT!
Alternatively you can go with a straight mix of 50% Black Rum & 50% Maple Syrup. Easier, just not quite as complex a flavor.
WELL oil one of your smoking grills, and place the tuna loins on that. It is best to ensure air flow both above and below the surface to the grill. You can now apply the glaze either by brushing on, or as I did with a squirter bottle.
This is a somewhat messy process, so make sure you cover the surrounding area with some type of protection. The glaze is very sticky!
Set up a fan so the air rushes over all sides of the lions:
Over the course of the next few hours the tuna will absorb the glaze. Add more glaze as it does so. You can choose to keep the surface of the loins moist through this, or allow the glaze to soak in and become dry to the touch between applications. Doesn't appear to make much difference except that keeping them moist will allow for better penetration. The drying process will vary, in this case they ran under the fan (with a lot of glaze sprayed on continuously) for over 24 hours (at 3 - 4 degrees C). At the end of that time allow a "patina" to form with the glaze. You must stop adding the glaze to induce this, and it will likely take several hours or so before it dries enough to form the patina
Smoking
The final step of course is the actual smoking. Regardless of how you do it, the internal temperature of your smoker should NEVER reach more than 70 degrees F - and cooler is indeed better.
Again, the temperature is CRITICAL! Do not overheat the loins, or they will dry out and be ruined!
I generally smoke them for around 5 hours, then pull a loin to test. Slice thinly and try the second or third slice in. That will tell you if you need more smoke or not. My general rule has become ~ 6 hours in the Cold Smoke all told to finish.
Remove from the smoker and allow to sit for a couple hours.
Then either vacuum seal or ENJOY!
Cheers,
Nog