Getting Technical: Milk Matters

By Dave Potter, co-owner and Technical Manager/Dairy Connection Inc. & GetCulture

When I think of high quality cheese, what comes to mind first is that it should be enjoyable and safe to eat. The characteristics that make cheese enjoyable are good flavor, aroma, texture and appearance. These same characteristics are also important when choosing the milk that is used to make cheese. The major attributes to consider when choosing or sourcing cheesemaking milk are microbial, protein and fat quality. When making most cheese types, it takes over one gallon of milk (about 10 lbs.) to make one pound of cheese. This means that your cheese is comprised of a ten-fold concentration of milk components (mainly protein and milkfat). Not surprisingly, these components are also the main contributors to flavor, aroma, texture and appearance in your cheese.

As noted above, it is important to find a good source of milk if you want to make good cheese. If you are a hobby cheesemaker, in most cases your choices are to buy from the local grocery store or farmers market, a local dairy farmer, or possibly you are fortunate enough to be able to get milk directly from your own cow or goat. In each case you need to know that the milk is safe and of high quality for the intended use. For example, the regular milk you buy at your grocery store may be of good drinking quality but it may not be optimal for cheesemaking.

What makes good cheesemaking milk and where do I find it?

Buying milk at the grocery store or farmer's market: Typically milk that is purchased from your local grocery store has been pasteurized and homogenized. Pasteurization is the heat-treatment of milk to kill existing bacteria (which may vary drastically between possibly beneficial to very harmful), while homogenization breaks up the larger fat globules in milk for a consistent texture and appearance. These processes ensure that the milk is safe and pleasant to drink, but can also cause problems with proteins and fat quality when trying to make cheese (more on that later).

For ultimate safety, your cheesemaking milk, whatever the source, should be pasteurized. That said, cheesemakers will want to avoid milk that is ultra-pasteurized (UP) or ultra heat-treated (UHT), which is milk that has been heated to very high temperatures. Such treatment, taken by many dairy processing facilities to assure that milk is safe to drink and to maintain the safety throughout the shelf life of the milk, will have a detrimental effect when it comes to cheesemaking as heat-treating milk at such high temperatures denatures (relaxes the structure of) milk proteins, causing problems with coagulation. For best results, just avoid milks labeled as ultra-pasteurized (UP) pr ultra-heat-treated (UHT) -- by U.S. law milk must be labeled as such. Milk that is more gently pasteurized to rid it of potentially harmful bacteria can often be found in any good farmer's market, well-stocked grocery or health-food store in your area that carries a supply of fresh, locally-sourced milk.

In addition, try to find non-homogenized milk, which is easily identified by the "cream-top" that develops as the larger fat globules naturally float to the top of the milk container. Homogenization can cause cheese to retain more water and be softer.

In contrast, ultra-pasteurized milk work well for making yogurt and fermented milks because the denatured proteins improve texture and appearance by holding in moisture and preventing the liquid whey from separating. However, in cheesemaking, we want the moisture to be removed and thus this process interferes.

Buying milk from a local farmer or obtaining milk from your own animal: If you are getting milk from a local farmer or from your own animal(s), you will want to take measures to ensure that it is free of harmful bacteria and that it is safe for cheesemaking. Milk that is not from a store (such as from a farm, depending on your state's regulation of milk) or from your own animal will often be raw, unprocessed (unpasteurized) milk. There is much discussion over the pros and cons of raw milk. I will not address those issues here, but will say that in cheesemaking we are purposely setting up an environment that is ideal for bacteria growth, so it's important that any harmful bacteria are not set up for success! If you prefer to use raw milk in your cheesemaking, be certain that adequate sanitation procedures have been followed in the harvesting and handling of the milk. Alternatively, you may want to consider heat-treating your milk using a low-heat, short-hold method to help reduce potential contaminant growth. Heat treatment is not as effective as pasteurization, but in theory is more effective than raw milk for controlling unwanted bacteria. The heat treatment process results in heating the milk to 145ºF for 30 minutes and then cooling it down rapidly. In essence it causes a reduction in the microbial count without denaturing the proteins, which some people find helps the quality of their product.

Beyond the issues of health and safety, the main point I want to discuss is that of microbial quality of raw, unprocessed milk as it relates specifically to product quality and traits. Raw milk will inherently have a microbial content of unknown organisms. These microbes, if not properly inhibited by immediate cooling of the milk once it has left the animal, will produce enzymes that will chew up the milk protein and milkfat, possibly resulting in undesirable flavors. Going immediately from milking to cheesemaking helps minimize this. Also, some of the natural bacteria in raw milk may compete against the starter cultures that you add to make the particular variety of cheese. In such a case the added bacteria may not be able to perform their job adequately and there may be a lack of the acid production necessary to make the cheese at all, and keep it safe for aging. This is the reason many raw-milk cheesemakers will do a gentle heat treatment to 140ºF for only a few minutes to reduce the number of unwanted bacteria before starting to make cheese. By law in the United States, they cannot sell this cheese for at least 60 days to ensure that any possibly unsafe organisms have succumbed to the low-pH environment of cheese.

Other differences in milks: In addition to using cow milk, sheep and goat milk is also commonly used. Milk components from these animals can vary somewhat among breeds, but primarily between species. Sheep milk contains almost double the amount of fat and protein as compared to both cow and goat milk. Yogurt made from sheep milk is of exceptional quality with little to no draining. Goat milk differs from cow milk in that the fat globule is smaller and tends to be “naturally” homogenized. Separation of cream is more difficult. In addition, the protein particle is not as complex or dense as compared to sheep and cow milk. It typically produces a softer texture in fresh cheeses because of this.

Another factor that can have an influence of milk flavor in all animal types is animal diet and feed sources. Typically, pasture-fed animals may demonstrate more aromatic attributes in the milk due to wild flowers, weeds and various grasses. These flavors may be beneficial or detrimental to the overall flavor of the cheese. Many of the volatile aromas are lost during pasteurization or heat treatment of the milk, but some flavor may still be present. Some cheesemakers take advantage of these flavors through rotational grazing. Larger cheesemakers will treat the milk to remove these flavors and aromas so they can make a more consistent cheese

Milk is a fascinating and complex food. Converting it into cheese provides an unlimited variety of flavors and texture changes, as well as challenges. Having a better understanding of the milk source and components will help you make a better cheese or fermented product.