Rennet and setting issues in cheese making
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Hi everyone, it’s Leon the Milkman here and today we are talking about rennet and how it sets milk if you have possible issues with the rennet-setting of milk how to solve them so either you have a problem with the milk or the rennet or both. So what issues can we have with Rennet? Well, firstly you could be using too little. So we normally need about 30 to 40 IMCU’s per liter of milk, so if I want to rennet 100 liters of milk and I’ve got liquid rennet with a strength of 600 IMCU, 600 divided into the 3000 IMCU I need to set the 100 liters of milk would give me 5 so I would need 5 milliliters of that 600 IMCU strength rennet to set the 100 liters of milk for which I need a minimum of 3000 IMCU. Also, we could be using the rennet at too low a temperature remember rennet is a stomach enzyme originally and even the microbial rennets need close to body temperature to function optimally um we could be using too high temperatures or hot water to make up the rennets and that would knock off animal rennet 40 to 41 degrees Celsius is normally already too much for animal rennet the microbial rennets can take it a little bit more heat. It could also just be that the rennet is too old, so we can do a little bit of a rennet, test we can take some raw milk heat it up to 35 Celsius in the microwave add a few drops of the rennet, and see if the milk sets. If it works then your rennet is still active then on the milk side um could be that your milk is diluted so there’s water addition that would dilute the protein and the soluble calcium both play important roles in the setting of the milk could also be that the milk is over-pasteurised so um when the milk is used for long life milk or UHT, ultra-high temperature milk then the temperatures are too high there is too much denaturation of the protein and the casein, the structure actually changes so with the rennet being an enzyme that fits like a key into a lock, when the lock changes the key doesn’t fit anymore so remember calves are not used to drinking UHT milk or long life milk they drink raw milk so the more the structure changes the less chance that the rennet will be able to do the job so some shop milk we can use we’ve got to do that little rennet test that I shared with you earlier. Yeah, so I hope that helped you on your way to solving your rennet setting issues in your cheese making. If not, please drop me an e-mail or join our Facebook group at cheese making and dairy science.
Leon the Milkman, all the best
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