Milk ... What it is ... What happens to it
and how does it affect the cheese we make

What is it?

Milk as we know it .....

Fresh milk from the healthy animal is about as good as it gets.
It contains it's own system of cultures and enzymes that make it very suited for the newly born and young as well as for cheese making.

The physical makeup of this milk is primarily:

Water (88%)
Lactose (4.5-5.5%) the milk sugar which serves as fuel for the lactic bacteria
Protein (3.5% in cows to over 8% in ewes) primarily the Casein for cheese structure
Fat (3.5-5% in cows up to 9% for ewes) providing flavor, aroma, and texture in cheese
Minerals such as Calcium which form the Casein bonds for cheese
Enzymes such as Lipase and Plasmin which aid in the ripening of cheese

These components in fresh milk are kept in a suspension due to the nature of the casein particle (milks primary protein) and these in turn trap the fat particles. This suspended particle condition will later be altered in cheese making via rennet, acidity, and heat.

It is this change in the casein structure which causes the white fluid milk to form into the firm jell which becomes the curd of our developing cheese.

This process can be either a controlled development of positive lactic bacteria populations (as in cheese making) or it can be the wild growth of wild bacteria that will simply result in the souring of the milk.

This quality and balance of milk components also makes possible the wonderful array of cheeses due to differing breeds, diets, seasons, and even geographic areas.

What can go wrong with it?

From the moment that the milk leaves the animals udder, things begin to change.

First, as the milk leaves it's healthy environment it enters a much harsher environment of possible contamination. It is here that the milk producer has a great ability to control the quality of milk by preparing and keeping a clean milking area and practicing a proper sanitation routine.

Next, in commercial milking, as the milk moves through the tubes, pipes, and pumps into the refrigerated tanks more physical changes begin to take place:
Fat globules can be damaged releasing enzymes that can cause problems in ripening
During long cold storage more of the Calcium can go into solution resulting in weak curds
Also, during cold storage certain undesirable bacteria that grow well at these cold temperatures can increase to very large populations.

Finally, as the milk is transported and then cold stored again, the above problems begin to accelerate.

Since the Lactose in milk is a very good food supply for many types of microbes, all of the above conditions translate into a deteriorating milk quality, so to preserve this milk for the public in a safe manner something has to be done.

What is being done for this?

In 1857 Louis Pasteur realized that heat treatment would destroy unwanted microbes and shortly after this the pasteurization of milk began in Europe and America. By 1940 this process became well established as dairy herds became larger, bulking milk became popular, milk travelled farther, and larger milk processing plants and cheese factories held milk longer.

There are several different approaches that will result in changing milk quality:

Thermization or heat treatment ... Is a low temperature (145F) and short time (15 seconds) that has the lowest impact on natural bacteria and enzymes in milk and is commonly practiced in Europe
Pasteurization can take one of two forms:
Low Temperature (145F) Long Time (30 min.)
High Temperature (162F) Short Time (15 sec.)

... At either of these points many of the enzymes and cultures are affected and Calcium damage has become apparent but the use of Calcium Chloride may reverse the later. Dairy technicians have tried to replace the enzymes and cultures through science but we all know that it is very hard to do as well as 'Mother Nature'.

one of the real downsides to pasteurization is that fresh milk naturally contains healthy bacteria that inhibit the growth of undesirable and dangerous organisms. Without these friendly bacteria, pasteurized milk is more susceptible to contamination.

We have all been led to believe that milk is a wonderful source of calcium, when in fact, pasteurization diminishes the nutrient value of milk ... making calcium and other minerals unavailable. Complete destruction of phosphatase is one method of testing to see if milk has been adequately pasteurized. Phosphatase is essential for the absorption of calcium.

Ultra Pasteurization
This is a range of milk processing temps from 191-212 F for varying times
once the temp rises above 174F the calcium component of the milk will be damaged to the point that a curd will not develop properly. If your curd forms as a loose mass or something looking like ricotta, then your milk source has been probably Ultra Pasteurized.

This higher heat treatment causes denaturation of whey proteins which subsequently stick to the casein particles. The effects are:
* Longer flocculation times
* Weak or no curd formation
* Poor syneresis (moisture release)
* Coarse textured curd with reduced ability to stretch, mat and melt.

Ultra High Temperature Sterilization (UHT)
(280F) Short Time (2 sees) ....
UHT when used to describe a dairy ingredient means that such ingredient shall have been thermally processed at or above 280 deg.F for at least 2 seconds.
The key word here is 'Shelf Life' and this process increases it to 60 plus days compared with the 18 days of lower temp pasteurization. It would be very hard to place the word 'Fresh' on the package with any conscience.

If you would like to see the visual difference in how UP and UHT milks differ
in the cheesemaking process clik here

FDA defines pasteurization as:


145 deg.F
161 deg.F


30 min.
15 s.


Vat Pasteurization

191 deg.F
204 deg.F
212 deg.F
1 s
0.05 s.
0.01 s
Ultra Pasteurization
Ultra Pasteurization
Ultra Pasteurization

280 deg.F
2.0 s
Ultra-High Temp Sterilization
If the dairy ingredient has a fat content of 10 percent or more, the specified temperature shall be increased by 5 deg.F.

So How did we get from this....

As the times change and our many diversified dairies dwindle to a few mega producers needing to hold the milk for longer periods shiping over long distances, 'Shelf Life' becomes a priority and UP or UHT milk are the tool of choice for these 'Mega Dairies'

... This milk has all of it's enzymes and cultures systems affected as well as damage to the Calcium balance.
Most importantly the Protein structure has been altered to the point that it is almost impossible to form a proper curd for cheese making.

Most cheese makers consider this to be dead milk.
It is about as close to 'Sterile Milk' as we can get.
There are no regulations that require labeling of this milk. At first the dairies were so proud of this technology they put it on of their labels but now with the negative feedback from their customers, many are no longer labeling it as such.
Many of our cheese makers have bought this unlabeled milk and had failed batches.
What can you do?
Talk to your store manager and ask him about the milk treatment and voice your opinion about this process.

.... To this

Options for Cheese Making Milk?

Farm fresh milk
This will be the best milk you can buy for cheese making, providing you do your homework and either produce or find milk that you are very confidant in quality wise. You will need to make sure the animals are tested, healthy, and that the milk handling has not opened this milk up to contamination.
This is very important and the decision to use this milk is totally in your hands.
If you decide to use this milk you then need to decide whether it should be used raw or with a moderate heat treatment applied.

In using your own raw milk it is very important that the milk is used fresh ... within 40-48 hours and that is kept cool enough that natural bacteria in the milk do not begin producing acid. If you are able to test your milk the aciditysould be in the range of .16-.20% and pH 6.8-6.7.

Pasteurized and Homogenized store bought milk.
We have made cheese from this type of milk for many years and Ricki's Mozzarella demonstrations almost always use this type of milk with great results. This is most often the only milk our customers can get.

The real problem is that milk is being shipped cross country after being processed by huge processing plants .. in order to do this the milk must be processed at higher temps and then held at cold temps for long periods while shipping long distances to markets .. this is especially true for our so called "organic milks" ... many of the milks not labeled as UP are in fact heat and cold damaged and will not make a proper cheese curd
.. our best advice to date is to buy a LOCAL milk ..
one that has not had to have the extensive "LongHaul" treatment. (Click here for comparison photographs of good milk curds vs UP)

Homogenization will have a small effect on cheese but in the case of blue cheeses this can be a plus. This process is normally done to reduce the size of the fat globule in milk to such a small size that it will not float to the top (remember cream top milk dad used to spoon off into his coffee). The process itself does a bit of damage to the fat globule membrane and will affect the flavor and texture a bit.

Nonfat Dry Milk plus Cream
Believe it or not we have had fabulous results in making our mozzarella from this combination. If you can not find good quality local milk give this a shot

Use a good quality Non Fat Dry Powder milk such as 'Carnation' brand. We have found that some NFDM produced in other parts of the world and sold through "discount" stores does not work due to the method in which it is produced (too high temperature for drying).
Choosing Non Fat Dry Milk Powder is important because the butterfat in Dry Milk Powder can turn rancid due to process damage and storage conditions.
Some Dry Milk Powder is made at higher temperature and results in a caramelized and sometimes other 'off' flavors. This milk may be fine for the baking and other food industries but not for cheese making

For 1 Gallon of milk ....

  • Mix up 4 quarts of NFDM powder according to manufacturers instructions
  • Let it re-hydrate overnight .. remove 1/2 -1 pint milk to make room for cream in next step
  • heat cream to 100F (1 pint light cream or half and half or if only heavy cream can be found use 1/2 pint) ... add this to your milk
    It is OK if the cream is UP because the calcium and protein curd making components will be found in the NFDM portion.

You are now ready to use this milk in making your cheese...

The next time you go shopping for milk,
talk with the manager and stress the following points.

(Click here for a list of talking points!!)

Jim Wallace 03/05