Making Yogurt – What Is Fermentation

In the case of Yogurt, fermentation is the conversion of carbohydrates (sugars) to organic acids by the action of bacteria. In yogurt made from milk, the carbohydrate is lactose (milk sugar) and the end result organic acid is lactic acid.

We have spoken before about the bacteria involved which can be one or more strains of the lactobacillus family or the streptococcus family. Now these bacteria just love sugar and they just eat it up – can’t get enough of it, and as they eat it they convert it to lactic acid which is what gives yogurt it’s tangy and slightly acidic taste.

But that is not all that happens. This feast for bacteria also coagulates or curdles the milk. What happens is that the proteins in the milk (casein) tangle together and form solid masses called curds. The remaining milk proteins form the liquid portion which is called whey. In milk roughly 80% of the milk proteins are casein which is why milk makes a lovely thick substance which we call yogurt.

For the fermentation process to occur, the milk needs to be kept at a constant temperature between 42 and 44 degrees Celsius – around 108 and 111 degrees Fahrenheit.  If the incubation temperature drops too low or goes to high, then the bacteria die and you can end up with an inferior end result.

I once had the temperature go too high while making a batch and I ended up with about 25% yogurt and 75% whey. Whey is the liquid made from milk protein that will sits on the top. Rather than waste the batch I just mixed them together and ended up with a tangy thick sort of milk and used it to make shakes.

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The History of Yogurt

There is evidence that yogurt has been used as a food for at least 5500 years. It possibly originated in the region around Bulgaria where the local name for it means “sour milk” brought about by spontaneous fermentation of naturally occurring bacteria. Interestingly, lactobasillus bulgaricus was named after Bulgaria because it naturally occurs there and is stll used to make yogurt to this day.

For centuries, the entire area around the Mediterranean and Black sea have been eating yogurt of many different varieties and textures. This area extended to cover Egypt, the Middle East and India. It is not difficult to imagine how milk left out in the sun would start fermenting and someone would dip a finger into the thickened milk and have a “eureka” moment.

In 1919 a Jewish businessman living in Barcelona began industrialized production of yogurt called “Danone” which means “Little Daniel” after his son. Later, when this brand expanded to America, it went under the name Dannon which is a yogurt that contains live bacteria and is available all over America today.

Yogurt was first introduced to America in 1929 by an Armenian immigrant family who founded Colombo & Sons Creamery in Andover, Massachusetts using a traditional Armenian recipe. This business was bought by General Mills in 1993, but yogurt is still made at the same location today. You can find more information on this at the Massachusetts History Society and at the Colombo Yogurt website.

In 1947 Dannon introduced yogurt with fruit jam added to the bottom of the container.

In 1950 health guru Gayelord Hauser pushed yogurt into the public consciousness when he published “Look Younger, Live Longer” where he claimed yogurt was a wonder food. As a result, by 1968, sales of yogurt had increased by 500%.

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