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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.
According to Food and Drugs  21 CFR131.110e(1)ii All milk fitting the definition must be labled as Ultra Pasteurized however The LAW states that this need only be 1/2 the size and no designation as to where it should be on the package ... SO... fine print and buyer beware here. We have had many write in who have purchased what they thought was regular whole milk to get home and discover the UP on the package

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





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New England Cheesemaking Supply Company
54B Whately Rd, South Deerfield, MA 01373
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