Is Vegetable Rennet Always Double Strength?

[soniaR]

Usually when a recipe calls for vegetable rennet, it also says "double strength". I found a recipe I'd like to try that calls for vegetable rennet but it does not say "double strength". My vegetable rennet is double strength. Can I assume that all vegetable rennet is double strength? Thanks.

[mikekchar]

No.  Unfortunately not.  It can be wildly different strengths.  Hopefully it lists the IMCU on the package.  For liquid rennet, "single strength" is 200 IMCU per ml (or 1000 IMCU per tsp).  I hope I don't get this wrong... I'm actuall *in bed* as I type this.... 1000 IMCU corresponds to the amount needed to coagulating 25 liters of milk.  The most popular non-animal rennet tablets I know of are Fromase 50 tablets that are rated at 2305 IMCU per tablet and coagulates 50 liters of milk.  You will notice that this is slightly more IMCU power per liter of milk than the standard calls for.   I think the standard works well for raw milk and I agree with Fromase's levels for pasteurised milk (or at least, this amount lets me hit my timings almost exactly).

If you see recipes that call for 1/4 tsp of single strength rennet, you can assume 250 IMCU.  Normally that's for 1 US gallon of milk which is 3.785 liters, or ~66 IMCU per liter.  Fromase's recommendation calles for 46 IMCU per liter and the standard calls for 40 IMCU per liter -- so you can see that most recipes over rennet.

Hope that helps!

[soniaR]

Yikes, that's a lot to digest, and it's not even bedtime for me! My vegetarian rennet does not say the IMCU. It does say that 1/8 tsp will coagulate 2 gallons of milk in 45 minutes.

This is the recipe I want to use:
2 gallons whole milk (I will be using organic non-homogenized milk)
¼ tsp.  Meso II
¼ tsp. Thermo C
½ tsp. calcium chloride diluted in ¼ c cool nonchlorinated water
½ tsp. vegetarian rennet diluted in ¼ c cool nonchlorinated water
Diamond Crystal kosher salt

That's a lot of rennet compared to what mine says! Maybe the best thing for me to do is try to contact the site where I found the recipe.

[mikekchar]

Unless my math is wrong, I think that works out to 580 IMCU per ml (2900 per tsp) -- so nearly triple strength rennet.   That is not an unusual strength for vegetarian rennet.  It can be made arbitrarily strong, I think.  I would just follow the instructions on your rennet.

[scasnerkay]

If you buy from the same source I think it is fairly consistent each bottle. I have always found it to be considered double strength compared to calf rennet. I have never heard of single strength veg rennet.
Checking your flocculation times will be a big help when using a new bottle of rennet. Then you can plan or adjust on your next make.