Yogurt characteristics are not only influenced by the culture used, but by the choice of milk. Milks from different animals and milks processed in different ways can result in differences in your yogurt's thickness and texture.
While most milk will culture well, there are some factors to consider. Keep in mind yogurt cultures want milk that has not been altered beyond simply pasteurization and homogenization. Powdered milks, lactose-free or lactose-reduced, or milk with additives such as Omegas (i.e. fish gelatin/oil) likely will not work.
How The Type Of Milk Affects Homemade Yogurt
Cow milk is the most popular choice for culturing. Heating encourages the proteins to coagulate, resulting in a thicker yogurt than unheated or raw milk.
Goat milk is becoming more popular for culturing. The structure of goat milk is different from cow milk and results in a thinner finished yogurt than cow milk.
Sheep milk is sweeter than cow milk and contains more protein, resulting in a thicker, creamier yogurt. It is used more for making cheese than for making yogurt.
Non-dairy Milk may be used to make yogurt. Please see our article, Alternative Milks for Making Yogurt for special instructions.
Lactose-free milk may not be suitable for culturing. Some brands do actually still contain lactose, but also contain lactase, an enzyme that helps lactose-intolerant individuals digest the lactose. However, these brands are usually ultra-pasteurized, as well, which does not work well for culturing. Other brands of lactose-free milk are filtered to remove lactose. In that case, there would be insufficient food for the bacteria.
Lactose-reduced milk may not be suitable for culturing. There will not be enough food for the bacteria, and it also may be highly processed.
There may be other options for lactose-intolerant individuals. Learn more about using long culturing times to reduce lactose in the final product.
Powdered milk may not be suitable for culturing or activating. It may have been overly processed or contains additives, which makes it difficult for bacteria to work.
How Milk Pasteurization Affects Homemade Yogurt
Pasteurized Milk can be heated to temperatures from 145°-212°F for various lengths of time, then immediately cooled to 39°F for storage and transportation. Pasteurized milk processed using any of these methods generally produces good results when cultured.
Ultra-pasteurized Milk (UP) or ultra-high temperature treatment (UHT), is heated to 275°F or higher for about one second. UHT milk is actually cooked, and is therefore unsuitable for culturing.
Raw Milk is not heated and contains its own set of original microorganisms. Since these microorganisms provide some competition with the bacteria in the yogurt culture, there are special considerations when making yogurt with raw milk. Because the milk is unheated, raw milk yogurt is generally thinner than pasteurized milk yogurt.
Many states place restrictions on the sale of raw milk. Please check your local laws governing the sale of raw milk, as it varies from state to state.
How Milk Homogenization Affects Homemade Yogurt
Homogenization is a treatment that prevents the cream from separating from the milk. Most cow milk available in stores is homogenized. Goat and sheep milk are naturally homogenized.
With non-homogenized milk the cream will rise to the top of the yogurt just like it does with the milk, so the top layer of the yogurt will be thicker and more yellow in color.
Please note that it can be more difficult to activate your starter in non-homogenized milk. We strongly recommend activating in a homogenized milk, and then later switching to a non-homogenized milk.
How Milk Fat Content Affects Homemade Yogurt
Yogurt made with reduced-fat milk will be thinner than yogurt made with whole milk. Commercially available low-fat yogurts include additives and stabilizers to make them unnaturally thick, or they have been drained of whey to make a thicker product.
Many yogurt cultures perform very well in half-and-half or even in cream, producing a rich, thick yogurt that is almost like sour cream. When using a reusable yogurt culture, make sure to retain some yogurt from a previous batch to use as starter. Cultured cream does not re-culture well, as the lactose content is very low.
What Will You Choose?
When it comes to milk, the possibilities are numerous, and the decision may be difficult if you have many varieties available. Try different kinds of milk until you produce a yogurt that suits your personal taste.
The choice is up to you!