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I was reading the Monterey Jack recipe in the recipes area.  It says to add salt to the rennet.  Why? What does this accomplish?  Thanks.

Don't know why, that was a recipe I copied down long ago and I don't know where it came from.

Looking for an answer, I found other jack recipes do the same, but I can't seem to find out the why of it.  LinuxBoy, come to the rescue!

You salt calf vells to preserve the rennet and maintain its strength. There is no reason to salt liquid rennet or commercial rennet preparations; they are already salted, typically at near saturation levels.

My Marschall M-50 Coagulant "Rennet" tablets instruction sheet says to add salt:

"To dissolve, add tablet of desired size and crush it in a small bowl. Add 1/4 cup distilled water per 1/2 tablet, mix until dissolved, then add 1 tsp. flaked salt."

Marschall is a microbial rennet substitute.  As such, it has a wider swath of casein cleavage sites, is more generally proteolytic, than calf rennet.  Though from what I've seen, among the microbial substitutes, the protein loss varies, when compared to calf rennet this non-specificity would, ceteris paribus, mean more protein is lost to the whey. 

Additionally, from what I've read, in theory, this can lead to a bitterness issue down the road, since many of the peptides resulting from this comparatively more non-specific hydrolysis are known to contribute bitter notes.  The jury seems to be out whether in practice this obtains - I know many have said they've no issue with bitterness using these, when making aged cheeses.  Perhaps it's a sensory threshold issue; I don't have any data on that.

From what I see, Marschall comes already salted, so I wouldn't know why you need to add more.  I have read that microbial rennet is particularly prone to Listeria contamination.  I suspect the salt added is used for the same purposes as in calf rennet, preservation.

Thanks. I'm not making any aged cheese yet, and by the time I'm ready to attempt some, I'll have my calf rennet.

Thanks LB, I knew when making it, salt preserved it, but couldn't see what additional salt would do. Glad to know it's probably just a carry over from the original recipe.