Danisco Marzyme 150 MG - Need help in understanding the enzyme activity better

[Taha Ahmed]

Hello,

I recently got Danisco Marzyme 150 MG microbial rennet and studying to begin making cheese. However, right now I'm struggling in understanding the activity of this enzyme and knowing the proportions of the powdered rennet that is to go with what quantity of milk.

The product spec sheet says 'Clotting activity = 2080-2305 IMCU/g'. I have spent good hours in understanding the correlation between IMCU/g and IMCU/ml but couldn't succeed much. There's no certain way of knowing how many grams do I need for a certain quantity (let's say 100L) of milk. I even referred to the standard IDF 157A but that has too much scientific jargon that goes way over my head.

The spec sheet at one instance states 'this rennet has double action in the cheese making process', what does this indicate about the activity level of the enzyme?

Lastly. the spec sheet also gives the average quantities of the same product used for 100L of milk in making different types of cheese, but the quantity is in terms of IMCU again and I have no sure way of measuring or calculating what it reflects to in weight.

'Acidified fresh cheese (300-900 IMCU), matured lactic curd (1000-1800 IMCU), Semi hard cheese (2600-3300 IMCU) ... Cheddar and Italian Semi hard cheese (5100-5900 IMCU).'

I apologize well in advance if this comes up as a very fundamental question, but I tried looking on this forum as well and couldn't find a good understanding of this IMCU. I have also attached the product spec sheet if anyone wishes to refer. Looking for someone who could help me out, thanks.

[mikekchar]

I don't know why the descriptions of IMCU are so cryptic.  You are not the first person to get very confused.  However, it's actually fairly simple.

IMCU stands for "International Milk Coagulating Units".  1000 IMCU of coagulating agent will coagulate 25 liters of milk. This means that you want 40 IMCU per liter of milk.  The powder gives you 2080 - 2305 IMCU per gram.  So one gram will coagulate about 50 liters of milk.  For different cheeses, you may want more or less than the standard, but I think their clarifications are needlessly confusing :-)  One of the downsides of pure powdered rennet is that it's basically impossible to measure for small applications.  For 10 liters of milk, you need 0.2 grams, which is fairly hard to measure precisely (unless you have a really expensive scale).

[Taha Ahmed]

It feels good to know I wasn't the only one struggling with understanding IMCU.

I want to thank you for putting it so simply that 40 IMCU is needed for 1 litre of milk. However, this brings me to my next question. The standard you mentioned must be for single acting rennet I suppose, which means since the spec sheet mentions the rennt is double action, its 1 gram would suffice for around a 100L instead of 50, am I getting this right?

Also, since you're right about measuring the minute powder quantities. How do you think would be to prepare a solution (rennet + non-chlorinated water) and then use to get the required amount. For example, if I wish to curd 10L milk, I'll have to need 0.2g of rennet powder. So what if I prepare a solution with 10g rennet and around 100ml of water, and then only using around 2 ml of it (half a tsp), I suppose if the solution is homogenous, it should deliver that 0.2g of enzyme to the milk. Or am I thinking wrong?

Need your valuable suggestion on this as well. Thanks once again.

[mikekchar]

"Single strength" vs "Double strength" is really only meaningful for prepared solutions.  I think you are reading marketing material ;-)  The only thing you care about is the IMCU.  Ignore everything else.  Basically, "single strength" is defined as 200 IMCU per ml of solution.  It's the minimal IMCU that you would get from preparing rennet liquid from a calf's stomach.  Rennet produced from bacteria, or genetically engineered yeast usually produces rennet that has around twice the IMCU and is known as "double strength", although that is often anywhere from 500-800 IMCU per ml, so it is *not* double strength *at all* (in some cases quadrupal strength!).  The term is absolutely meaningless and doubly so when you talk about powder.  Just follow the IMCU.

You are correct that you can dissolve the powder in *non-chlorinated* water and then use the fraction of the water that you need.  Unfortunately, the rennet only lasts minutes once you add it to the water, so you have to throw the rest of it away.  But, yes, that is definitely what I would do -- and how most people use rennet tablets when they only want to make small cheeses.  Keep in mind that these powders have a lot of filler in them and some of the filler often doesn't dissolve.  The rennet will dissolve fairly quickly, so don't worry if it seems like it hasn't all dissolved.  That's totally normal.