Choosing Milk for Making Yogurt
Some of yogurt’s characteristics come from the type of culture that is used. Greek and Bulgarian yogurts are far different from filmjölk and piimä, for instance. But the type of milk you choose will also have a great effect on the way your yogurt turns out.
There are certain qualities, such as fat content, that would make obvious changes in the finished product. But there are additional qualities that make a difference in taste, consistency, texture, and quality.
The Characteristics of Milk
Cow milk is the type most of us in America are familiar with. It is generally the standard against which other milks are compared.
What Animal Produced the Milk?
Yogurt cultures can thrive in any animal milk, but there are distinct differences between the milks of different animals. Most of our customers use cow or goat milk for their yogurt production.
Goat milk has a taste similar to that of cow milk, although some people find goat milk that is not fresh to have a pungent “goaty” flavor. When a male goat is in a herd of milk-producing female goats, that can affect the flavor also.
In goat milk, the fat globules are extremely small (about one-fifth the size of the globules in cow milk), and stay suspended in the milk rather than rising to the top as in cow milk. This gives the milk a natural homogenization, and a creaminess similar to whole cow milk.
The casein in goat milk is a different kind than what is in cow milk.
Goat milk is more alkaline than cow milk, and tends to be whiter. It contains slightly less lactose, protein, and fat than cow milk, and slightly more water. It contains about 13% milk solids, and the curd that forms is softer than what forms with cow milk. As a result, yogurt made with goat milk tends to be less firm than yogurt made from cow milk. (However, using a chèvre culture with goat milk produces a thick, yogurt-like product that can be strained to make chèvre cheese, or left as is to eat like yogurt.)
Sheep milk is sweeter than cow milk and is used more for making cheese than for making yogurt. It is higher in fat, lactose, and milk solids than cow milk, and makes a very rich yogurt. The fat globules are smaller than those in cow milk, providing natural homogenization. Sheep milk contains over 19% milk solids and makes a firm curd that is more friable (crumbly) than cow milk curd. It has a higher casein content than cow or goat milk, and thus coagulates faster. The type of casein is more similar to that of goat milk than to that of cow milk.
Buffalo milk has about 11% more protein than cow milk, and almost twice as much fat (but only about one-fifth as much cholesterol). Buffalo milk is pretty hard to get, as there are only a few buffalo dairies in the United States. However, buffalo produce around 15% of the world milk supply as they are quite common in Southeast Asia, South America, and India. Buffalo milk is very rich and a little sweeter than cow milk.
Milk in its natural state is a very friendly environment for bacteria of all sorts. If exposed to pathogenic organisms, milk can become overloaded with bacteria that might cause illness. Milk that is stored badly, or that has to travel long distances, can easily become contaminated and dangerous to consume.
The UHT process can also be called flash pasteurization.
Microfiltration, also called “extended shelf life" pasteurization (ESL), is a process that partially replaces pasteurization and produces milk with fewer microorganisms and longer shelf life without a change in the taste of the milk. In this process, cream is separated from the whey and is pasteurized in the usual way, but the whey is forced through ceramic microfilters that trap 99.9% of microorganisms in the milk (as compared to 95% killing of microorganisms in conventional pasteurization). The whey then is recombined with the pasteurized cream to reconstitute the original milk composition. Microfiltered milk behaves similarly to pasteurized milk in culturing.
Raw milk is not treated with heat before delivery to the consumer, and contains its original microorganisms. These microorganisms provide some competition with the yogurt organisms, and the milk is sometimes difficult to culture. When making yogurt with raw milk, you must either heat the milk yourself to reduce or eliminate the natural bacteria, or go through some extra steps to establish the strength of the yogurt culture before inoculating the raw milk. Yogurt made with unheated raw milk is often thinner than pasteurized milk yogurt, both because of the competing microorganisms and because the unheated protein molecules are more durable and less likely to coagulate.
Raw milk in a container separates easily into a rich layer of cream that sits on top of a larger, low-fat milk layer. The fat globules rise to the top of a container of milk because fat is less dense than water. They rise rather quickly because the individual fat globules tend to form into clusters containing about a million globules, held together by a number of minor whey proteins. These clusters rise faster than individual globules can. The fat globules in milk from goats, sheep, and water buffalo do not form clusters so readily and are smaller to begin with, so the cream is very slow to separate from these milks.
Milk is often processed by removing the cream, which is then used (or sold) as a separate product. The cream can be skimmed by hand, or separated from the milk rapidly in centrifugal separators. The amount of fat left in the milk describes the milk: whole milk (standardized to 3.25% fat), reduced-fat (2% fat), low-fat (1% fat), or skim (no fat). Some dairies sell "full-fat" milk with 3.4% fat, which is very close to its original composition.
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. Yogurt can also be made with unhomogenized milk, raw milk, whole milk, reduced-fat milk, skim milk, or even powdered milk. You can also use other creamy substances such as rice milk, nut milk, soy milk, coconut milk, etc.
The choice is up to you!
|Cotton Bag for Making Soft Cheese|