Curing Roe

[MuskieBait]

Skein is probably the easiest to treat. I usually just shake some non-iodized salt (natural sea salt being best) and let the skein cure in that salt for a bit until a some of the moisture has come out, then I would let them air dry just a little before cutting into little chunks and package them into ziplock bags in portions that I would use for a trip. You can store them in the freezer for years. I still have steelhead skein from 4 seasons ago and they are in the same shape in the ziplock bags as they were when they were packed.

Loose roe is the trickiest. Like you, I have not had much success. I've tried almost every cure (except commercial ones) on the internet. I've tried boiling them in a saturated borax solution too. None of them really did that well in the freezer, even if you had let them air dry in the fridge for a few hours.

Now, I'm a graduate student studying cell biology. Part of what we have to do sometimes is to freeze cell cultures for future use. We freeze cells down to -80C or -140C regularly. One of the most damaging effects of freezing biological matter is the formation of ice crystals. Microscopic sharp ice crystals can pierce the cell membrane, and when the cells are thawed later, the cell content just leak out of the cell and you get a bunch of dead cells (which is no good to us at all). To mitigate that, we either freeze bacterial cells in a solution with glycerol, or we freeze mammalian cells in a solution of serum and dimethyl suloxide (DMSO). The serum is very rich in protein such that there is a very high protein to water ratio...such that the % water is low (or lower than simply water solutions). Simply put, the use of serum helps to minimize the amount of water. The DMSO is a cryoprotectant, which helps to slow the freezing process and thus it helps to prevent the formation of sharp ice crystals.

Well, you usually don't have access to DMSO...and I don't recommend people going out to get it either. And don't start with your vampire ways trying to drain people's or pet's blood to get serum. No, no...

But with some kind of background and experience under my belt, I got thinking one day...is there a way I can use household ingredients to help protect salmon eggs in the freezer? After all, salmon egg is just one very big cell with similar properties...

So...here is what I tried and why...

*** The following is only based on one "experiment" or trial. It worked, but...is it a freak success? Try it out, but if it end up not working, you just read the DISCLAIMER!!!

1) I heated up a pot of water to make a saturated solution of salt. You know it is saturated when more salt cannot dissolve. I let the water cool down a bit (but still a little warm) and then pour the eggs in to soak in this solution for a hour. The curing stage is basically to help the membrane of the egg to toughen. Some of the liquid will be extracted form the egg, so you may see a little bit of wrinkling, but then some of the salt solution will also be absorbed into the eggs. Let the eggs soak for an hour.

2) When the eggs have adequately cured, you can test by picking one up and squeezing them with your finger. I would suggest trying this before you cure the eggs so you have an idea how easy it was to burst the eggs, and trying this after you cure them to see how much more force you need to apply to burst them. Once they are cured, you can let them air dry a bit.

3) After the 1 hour of soaking, strain out the eggs. Take a cookie sheet and put a layers of paper towels on the cookie sheet, then pour the strained eggs onto the cookie sheet to air dry. Make sure the surface of the egg is dry! Roll the eggs around a bit so the bottom side of the eggs get to dry too. I usually remove the wet paper towel and put some new one so the eggs dry adequately.This is important because you wnat to remove any moisture on the surface of the eggs. Remember, any water/moisture on the surface is potentially bad since ice crystals may form.

4) Now...this is my experiment. I need some sort of cryoprotectant that can minimize the contact of water on the surface of the egg, and something that can freeze slower so ice crystals inside the egg does not form (remember, the salt cure also helps since salt has a lower freezing point...that is why roads are salted in the winter). So...I thought about oil...

Oil is a substance that remains liquid at room temperature. It has a freezing point of -10C. The beauty about oil is that it is hydrophobic...which in simple terms it doesn't like water and doesn't mix well with water. So, my theory is that if you have a dry surface that is coated with oil, water should not be able to penetrate this surface at all. That is why any waterproof seal uses silicon as waterproofing...that is why sometimes you use greased bearings in trailers to prevent water intrusion. Silicon and grease are both hydrophobic.

Another great thing about oil is that it can be incorporated into the cell membrane. Our cell membrane is basically a double layer of fatty molecules. Some areas of the membrane needs to stay a bit fluid, so more oil like molecules are often added in to keep this membrane fluid. Some areas of the membrane may need to stay rigid (like lipid rafts), so more grease like molecules are added to keep it more rigid. Well, I thought maybe using oil can also help since the oil molecules may be able to get incorporated into the egg membrane and keep it more fluid, thus reducing the chance that the membrane would burst. Just the concept of oil being very close to and interacting with the membrane was also a good idea since it may displaces water from the surface of the egg. It's a win-win, right?

Now, I took my salmon eggs that had air dried and dump them into little container that I have (in my case, they are capped test tubes I got from the lab...baby food jars would work too). I put enough eggs to fill it about 80% full. Then, I took regular vegetable oil and slowly pour it into the container, making sure to shake out any air bubbles that are present, and made sure to completely submerge the eggs in oil such that they are not exposed to air. I let the eggs sit in the container in oil for about 2 hours in the fridge. I let them sit so that if there is still moisture in the water, some of the oil molecules will form little spheres around the water and exclude them. I also shake them a little to make sure absolute no air is in between the eggs. If there is air, there is an exposed surface where moisture can leak in when the eggs are in the freezer. You have to make sure there is absolutely no air!

5) Then I put all the containers in the freezer and let them freeze. You will notice that the eggs freeze very slowly in this oil. This is wonderful since you now have a slow freezing process. The addition of oil probably also infuse into the egg membrane and help to keep that membrane more fluid too. Just a guess, but a pretty educated guess on my part.

How did they turn out?

I froze the eggs in late September. A month later, I was going to do a day of steelheading in November, but then work got in the way and I didn't have a chance to fish. Regardless, a few days before my planned trip, I took out a container of eggs and let them thaw out in the fridge. The oil has freeze into this gummy state, but it certainly was not complete solid. The oil thawed out before the eggs, and the eggs did freeze solid. However, the eggs did not burst at all after thawing, and they remained firm to the touch. They had a wonderful nature colour to them...although much of the scent isn't really there until you burst one. Overall, I find that this method was able to preserve the natural look and feel of the salmon egg. I have yet to fish with these, but at least the roe is does not thaw into a gummy mess. You can at least tie them into spawn bags.

Since I didn't get to go fishing in November and I thawed out a container of eggs, I thought about doing more experiments on them. I pour some out into a fresh container and pour some water into the container so now the eggs are submerged in the water, much like a real fishing situation. I want to see if the content of the eggs would eventually leak out and you would end up with an empty sac (which would suggest that ice crystals still formed and the membrane was pierced). I had these eggs soaking in water since November and I just checked on them now and they were still full and firm to touch. It's bloody amazing! Mind you, this was just tap water, which has chlorine and it is generally bad for the eggs. Eggs usually turns milky white when soaking for too long in the water. These eggs of mine turned a bit milky white, but they still have some peachy colour after almost 10 months in the fridge in the water!!! It's amazing! The other eggs that was soaking in oil in the fridge for almost 10 months were just beautiful...look just like the day they were put into the freezer last September. They are translucent and still firm to touch. In fact, I can throw them hard against the kitchen counter and they hold up in shape without bursting. None of them turn rotten, probably because the eggs were soaked in oil the whole time.

Now...here is a little suggestion...cod liver oil...that's all I'm gonna say.

OT, try it out and let me know how it work? Michael, if you like some roe for your river fishing, let me know and I'll give you a container's worth.

That was one long post...