Milk Cooling- It’s So Important!

I have been asked why I cool my milk in an ice water bath inside my fridge.  Well, simply, it's the fastest way to get milk cooled that I have available to me, and having the ice water bath inside the fridge makes it so I don't have to remember to transfer the milk to the fridge after it is cooled.  It takes up a fair amount of space in the milk fridge, but having quickly cooled milk is essential to the best quality raw milk.  The speed at which milk is cooled can have a great effect on how long it lasts and how good it tastes.  I want the milk from my cow to last at least a week, if not longer, and to taste excellent.  When I first started home dairying, I had goats and cows, and came across this excellent resource in one of my goat milk cheesemaking books.  It has since been published online, and so I decided to share the link here.  

Milk Cooling- It’s So Important!

And here it is, cut and paste:

Are you getting good grades when it comes to cooling your home milk supply? One of the most important factors in great quality milk is how quickly the milk is cooled.

Milk is perfect medium for bacteria (that’s why it works so well for cheesemaking).  Unless you are doing a good job of cooling the milk to slow down the development of harmful bacteria, they can be multiplying by the millions. This is even more important if you are using your milk raw. Pasteurizing the milk kills E Coli as well as many other harmful bacteria.

How close to Grade A are your milk cooling practices?  Many of you have various ways of handling your milk and think you are doing a good job.  Have you taken the temperature of your milk to be sure that it is getting cooled quickly?

If you are at least a Grade B give yourself a pat on the back.  This rating is very good for home use.  Most of us cannot meet Grade A standards without the use of commercial coolers.

I did some milk cooling testing to find out just how quickly each method cooled the milk.  Below are the results.

Grade A:

The milk is placed in bulk cooling tanks, which are refrigerated, and the milk is quickly cooled while being stirred.  This method assures the milk will be at 40 degrees in less than 30 minutes.  Usually it is at the temperature instantly then held to just above freezing.

Grade B:

Milk is placed into containers small enough to place into tubs or a sink of ice water.  This is acceptable for home use.  This method cooled the milk to 48 degrees in 30 minutes, 42 degrees in 60 minutes and 40 degrees in 90 minutes.  Results would be considerably better if some form of stirring the milk could be used to speed up the cooling.  Using a home pasteurizer would do an excellent job too.

Grade C:

Milk is placed in a small container and placed in a sink of very cold water with the water being changed 2-3 times during the cooling process.  Water temperature from our well here in Michigan comes out at 50 degrees.  If you live in an area where the water comes from the faucet even warmer, this would not be a great method to use.  The milk would only get as cool as the water.

Grade D:

Milk is placed in the freezer.  I tested a one-quart jar and it took 30 minutes to reach 66 degrees.  In 60 minutes it was at 50, in 90 minutes it was 43 degrees and finally after 105 minutes it was at 40 degrees.  If using a container bigger than 1 quart the results would be even worse.

Grade E:

Milk placed in 1 quart jars and put into the refrigerator.  In 30 minutes the milk was at 76 degrees.  In 60 minutes it was at 67 degrees, after 90 minutes it was 59 degrees.  3 hours later it was at 51 degrees and finally after 8 hours the milk had reached 40 degrees.  This is way too long.  By now the bacteria count has become very high.  Results would be even worse if using containers bigger than 1 quart.  Many home dairies use this method, but this is the absolute worst way to cool the milk.

By Mary Jane Toth, author of A Cheesemaker's Journey and Goats Produce, Too!