Originally a simple fermented dairy product, yogurt now has many variations and personalities. It can be thin and runny, or thick and firm. It can be made from cow milk, goat milk, sheep milk, nut milk, soy milk, rice milk, and from numerous other creamy substances. In some countries the milk of buffalo, horses, yaks, or camels is used.
For most of this discussion, we’ll refer to yogurt in its original form: a fermented dairy milk. This was how yogurt was first developed, and most of the yogurt in the world is made this way.
Essentially yogurt is the product of beneficial bacteria fermenting milk and turning it into a thickened, acidic food that will stay fresh longer than milk itself, and that contains millions of bacteria that are welcomed by the human gut.
The History of Yogurt
The word yogurt comes from a Turkish word meaning to curdle or to thicken. Today it is spelled yogurt, yoghurt, or yogourt, with yogurt being the most common American spelling.
It’s probable that the earliest yogurt was made by accident in Mesopotamia around 5,000 BC, when milk-producing animals were first domesticated. The milk was likely stored and transported in bags made from the stomachs of these animals, and the digestive juices and bacteria in the stomach linings made the milk coagulate and become acidic. Not only was it a new and interesting food, but the acidity helped to keep it edible for longer than if it had just sat out in a bowl or jar.
There is also some evidence of yogurt being used as a cleaning product and a beauty lotion as early as 2000 BC. The acidity of the yogurt helps clean away dirt and rust, and also helps clear away dead skin and nourish healthy skin cells.
Yogurt was a popular food in the Middle East for thousands of years, and has been a staple of the Eastern European diet. It’s now eaten throughout the world, as a main course, a snack, an ingredient in many recipes, and a condiment. It has gained considerable popularity in America in the last forty or fifty years, in keeping with general trends toward organic, cultured, and nutrient-dense foods.
Yogurt can be mildly tart or quite sour, and can be thick enough to stand up on a plate, or thin enough to pour, or anywhere in between. It contains protein and calcium as well as a variety of vitamins. Additionally, the process of yogurt fermentation is very similar to the process of digestion, so it can be easily consumed.
Many people eat yogurt plain, while others prefer to mix it with fruits or vegetables, or to add flavors or sweeteners. It is used in a variety of recipes as a flavor enhancer or leavening, and frequently enjoyed as a refreshing drink.
Not only does yogurt contain the same amount of protein and fat as the milk from which it is made, it also contains calcium, riboflavin, vitamin B6, and vitamin B12. While numerous claims have been made regarding the health benefits and digestibility of yogurt, we don’t comment on medical, health, or nutritional qualities of our products. However, a great deal of research on the subject is readily available on the Internet and in dozens of books.
How is Yogurt Made?
True yogurt is made from animal milk. Theoretically, the milk of any mammal could be used to make yogurt.
With care, yogurt cultures can also be used to ferment and coagulate non-dairy “milks” such as the creamy liquid obtained from nuts, rice, soy, or coconut. While these products are technically not really yogurt, they can be used and enjoyed just like dairy yogurt, alone or in recipes.
Put very simply, the process of turning milk into yogurt involves fermentation. Certain types of bacteria act on the lactose (milk sugar) that is in milk, and produce lactic acid. The lactic acid lowers the pH of the milk, and causes the milk protein to coagulate and make a firm mass. The acidified milk is an inhospitable environment for destructive bacteria, so the yogurt stays fresh longer than untreated milk.
The bacteria that does this is called beneficial bacteria, because it supports digestion and is nourishing, as opposed to pathogenic (harmful) bacteria that causes disease. The beneficial bacteria is called probiotic. It is similar or identical to the type of bacteria that lives in the human gut, which is responsible for the process of food absorption. When you use live cultures, the probiotics stay in the yogurt, and the yogurt can then be used as a starter to make more yogurt.
Yogurt and Other Fermented Dairy Products
There are many different ways that beneficial bacteria can be introduced to milk and make an entirely new food. The main difference between the different fermented dairy products is the bacteria used to make them, resulting in different flavors and consistencies.
Yogurt can be cultured with a variety of different bacteria combinations, each of which gives the yogurt a characteristic taste and consistency. There are typically somewhere between the range of two to six different bacteria strains in yogurt, and they are similar to the bacteria found in the intestines.
Kefir is a thickened milk made from little clumps of yeast, bacteria, and milk proteins that ferment the milk. There are about thirty different bacteria strains present in kefir grains. It has a slightly sour flavor and sometimes a faint effervescence. Koumiss is a similar product, made from mare’s milk.
Buttermilk is the name given to the whey that’s left over when butter is made, but it more commonly refers to a milk drink made by adding bacteria to low-fat milk, producing a thickened product with a tangy flavor.
Sour cream is cream or high-fat milk that’s been cultured and thickened. It’s very slightly sour, and usually quite thick. It was originally made by letting fresh cream thicken naturally as a result of fermentation from the bacteria present in the cream. When cream is pasteurized and has no natural bacteria present, it must be fermented with added bacteria.
Crème fraîche is a European-style sour cream, slightly sweeter than what we are used to in America. It’s also made by letting raw cream thicken naturally, or by adding buttermilk cultures to cream. Crème fraiche can be heated without curdling, unlike sour cream.
In recipes, you can often substitute one cultured milk product for another and get similar results. In fact, sometimes it is hard to tell the difference between a thin, tart yogurt and a thick, sour kefir or a creamy buttermilk!
Soft and hard cheeses are also made by culturing milk over a longer period of time. Some cheeses can be easily made by straining the moisture out of yogurt or sour cream, while others require additional fermentation and culturing steps.