Choosing Milk for Culturing Projects
You receive your cultured dairy starter culture and now all you need to do is add it to milk and allow it to ferment for your favorite cultured dairy treat. So you head to the dairy aisle of your local market. And there, in front of you, is an entire wall of various milk varieties. Unless you’re familiar with all of the terminology you may be confused on which type of milk to choose from for your cultured milk project.
Here are some of the terms you might come into contact with and some information about the effect different types of milk may have on your cultured milk product.
Skim. Skim milk is whole milk that has had the cream skimmed off of the top. It is generally fat-free or nearly so and is very thin in texture when poured.
Skim milk tends to make a very tart and thin yogurt or kefir. It also tends to be grainy and have a less-pleasant mouth feel as it lacks the creamy richness that tames the naturally occurring acid-creating bacteria.
2%. Milk labeled 2% means that a portion of the cream has been removed and 2% of the volume of milk you purchase is made up of dairy fat.
Cultured products made from this milk tend to fall right between cultured products made from skim milk and those make from whole milk, obviously. These products will be less grainy and tart than those made from skim milk but not quite as rich and smooth as those made with whole milk.
Whole. Milk labeled whole contains around 3.2% to 3.8% fat, depending on the type of cow being milked. Commercially sold whole milk is generally standardized to 3.25% milk fat. Whole milk has left the cream of the milk intact with the rest of the milk.
Whole milk makes the most pleasant-tasting cultured dairy products as the higher fat content works well with the cultures to create creamy, smooth yogurt and kefir.
Pasteurized. Milk labeled as pasteurized has been heated using a high-temperature, short-time method. This method of pasteurization forces milk through narrow tubus under high pressure, then heats it to 161°F for 15 to 20 seconds. Pasteurization is usually done to kill all bacteria in the milk and to increase shelf life.
Pasteurized milk can have a different flavor than unpasteurized milk, most notably a “cooked” flavor that may come through in your cultured dairy products.
Raw. Milk labeled raw has not been pasteurized. Many states do not allow the sale of raw milk on grocery store shelves and some states even ban farmers from selling their fresh raw milk, so this may difficult to come by.
Raw milk tends to stay fresh for a shorter time than pasteurized, generally only a week to ten days, after which it will begin to culture naturally. Raw milk often comes from cows allowed to graze on pasture, which can give the milk a unique flavor, depending on what the cows are grazing on.
Vat Pasteurized. Also called thermization or thermalization, vat pasteurizing is a process that heats the milk to 140° to 150°F for 15 to 20 seconds, then cools it again. This reduces the number of microorganisms in the milk, but not to the same degree as pasteurization. The milk is not pressurized before pasteurizing in this process. The FDA considers thermized milk to be raw, while the European Union considers it to be pasteurized. The behavior of thermized milk in culturing would be between pasteurized and raw milk.
Ultra-Pasteurized. Milk labeled as ultra-pasteurized has gone through a process in which the milk is pressurized, then heated to 275°F for about one second. This heating (actually cooking) of the milk extends the shelf life to the point that it can stay reasonably fresh even without refrigeration for much longer than ordinary pasteurized milk.
Because it is a cooking process, though, the milk is sterilized and fairly unsuitable for culturing. If UHT milk is the only variety of milk available, we recommend using a direct-set variety culture such as our Traditional Flavored Yogurt Starter or our Mild Flavored Yogurt Starter. The nature of UHT milk makes it difficult to perpetuate over time, so re-culturing starters such as Bulgarian, Greek, Viili, etc., are not the best choice here.
Homogenized. Milk labeled as homogenized has gone through a process to prevent the separation of the cream from the milk.
Milk straight from a cow will separate into a two layers: the top layer is a thick cream and the bottom layer thinner “skim” milk. This occurs naturally as a consequence of the lower density of the dairy fat than water. It should also be noted that milk from goats, sheep, or water buffalo tend separate much more slowly if at all.
The homogenization process pumps the milk at high pressures through very narrow tubes, breaking up the fat globules. Since a greater number of smaller particles possess more total surface area than a smaller number of larger ones, the original fat globule membranes cannot completely cover them. Casein clusters are attracted to the newly exposed fat surfaces, so it is much harder for the fat globules to separate from the milk.
Homogenization can give milk a creamier mouth feel as well as a blander flavor that will come through in your cultured dairy products. Unhomogenized milk when allowed to culture will generally have a slight separation in which a creamier, possibly yellow layer will develop at the top. This is easily stirred in, just like “cream-top” yogurts on the market.
Choosing Milk for Cultured Dairy
Culturing is a process that involves specified bacteria changing milk into a living entity that people love to eat and serve as nourishment to their families.
Cultured dairy products, like all food, are at their best when the ingredients are the purest and freshest you can source.