Freezing Rennet

[Varg Stigandr]

Can you freeze rennet?

Shipping is expensive and unreliable where I live, which makes buying a lot of something and storing it long term very attractive, and the local climate makes freezing a very cheap way to store things.

From what I've read, freezing liquid rennet is a bad idea, but what about the dried stuff? Has anyone had any luck using dried rennet post-freezing?

[mikekchar]

Tablets and powders are probably the best choice if you are going to freeze. The trick is getting the dosing right.  Normally you put a measurable amount in unchlorinated water, then add *some* of that water to your milk, throwing away the excess (it doesn't last).  This gives you good control.  Something like Walcoren tablets are a decent strength for doing that (you break them into 4).  Most powder is crazily strong, but there are low strengths powders -- I just don't know where to buy them.

I seem to remember someone saying that freezing liquid rennet *once* is probably fine.  Hopefully that person will show up to verify or not :-)

[Mornduk]

Nowadays I only use frozen powder rennet, this one.

It is cheap, easier to store and use than the liquid one, and if shipping is an issue, just one bottle will last forever (as in 3750G or 14.2k L if you buy the 500g bottle).

I keep it in the freezer and use 0.8g for a normal 6G batch. That is very easy to weight accurately with the normal equipment you should have already to weight cultures, etc.

It has the IMCU information so you can do the math easily. Or base it in my 0.8g/6G which is 40 IMCU/L. Or just think that those 0.8g are equivalent to ~ 4.5ml single-strength rennet and go from there to adjust according to your recipe.

[mikekchar]

So that works out to 1136 IMCU per gram, if my math is right, which is not bad.  I really should switch to that when my liquid rennet runs out.  Given the crazy shipping prices to Japan, it would be very cost effective to just buy the 500g bottle and, as you said, be set for life....  The only real problem for me is that I often do 2 liter semi lactic makes where I need a grand total of 20 IMCU :-)  But dilute and discard would still be fairly cost effective (0.1 grams would cost 2 cents).

[Mornduk]

It's 1150 IMCU (your math is right, I just said 0.8g instead of 0.789^). You could do 0.2g, take 1/3 of the dissolved volume and still have a really cheap rennet. In fact you could just store the other 2/3 in the fridge if you're using it soon enough so you're not wasting anything

I expected it to be worse than the normal one but it works just the same for me.

[stephmtl222]

For those who use powder rennet, do you know what type/origin it is ? Microbial ? Fermentation ? Curious to know if it is as specific as chymosin.

I (or somebody I won't name...) accidentally froze liquid rennet. I found it a few months later (don't know when it was placed in the freezer). I first thought I would toss it but I decided to thaw it and try it and, to my surprise, it was working very similarly to my fresh rennet. I have never really tested the activity compared to the fresh rennet but it definitively still work, and kept working for several month after thawing. I would not freeze it again as enzyme/proteins are really sensitive to freeze/thaw cycles.

[mikekchar]

The one Mornduk references is calf rennet, but there are all sorts available.