How Not to Damage the Protein in Milk

Protein in milk comprises two groups: casein that we cheese makers want and whey proteins.  Whey protein is more water soluble and does not form large structures like the micelle chains of casein.

Preserve Your Yield

All cheese makers know that the higher the level of protein (casein) in milk, the higher the yield of curd, so we want to be gentle with our milk and not damage the casein element of the protein.

Excessive heat

Heat damages casein.  The optimum level for pasteurisation is 72 o C for 15 seconds, if you were to pasteurise at 72 0C for 20 seconds, you will damage the protein.  If you pasteurise too high, you will caramelise the lactose and destroy the casein micelles.  The milk will also smell sweet.  The micelles will not stick together and you will have a very crumbly cheese.  I know, we’ve been there!

Whether you are batch pasteurising or have a continuous flow pasteuriser, try not to over heat the milk. 

Minimise Pumping and Rough Stirring

Extreme activity such as too much pumping or agitation will damage casein, such as having pumps and pipes not designed for a smooth flow.

If you damage the protein, you will have a less firm coagulum.  The best cut is from unpasteurised milk that has not been subject to pumping and pasteurisation.

Stirring cold milk will damage protein and too vigorous stirring will also damage it; be gentle.

And we have seen that homogenisation destroys the protein structure and you will generally not be able to make a good cheese out of this.

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