Cultured milk products are just about as old as the domestication of sheep, goats, and cows. Created originally in the highlands of Central Asia by ancient nomadic tribes who were dependent on dairying, they weren't just thickeners--they were an important and concentrated source of nutrition...that didn't spoil and that could be easily stored and transported. The culturing of milk and cream into cheeses, yoghurts, and sour creams were spread by these pastoral and warring tribes in every direction, to the borders of China. to India, and into Europe. Some places embraced them; others held them at arms length. You'll find them in the soups of cultures that loved them: Northern and Eastern Europe, the Balkans, Greece, Turkey, the Middle East, Afghanistan, Northern India, and back to Central Asia.
For a Swiss folktale that highlights the importance of milk in the Swiss culture, click HERE...and you'll read "How the Kuhreihen Began."
A handy and rich addition to soups because its proteins have been greatly diluted by fat globules and are less likely to form a skin (like milk does) when heated or boiled. It is also fairly immune to curdling in the presence of acidic or salty foods.
FoodTale: The word "cream" comes from the Greek "Chriein," which means "to anoint." This word is also the root word of "Christ," the "Anointed One."
Mary Bruce of Brunswick, Maine, cites this as a good and healthy substitute for cream as a soup thickener, adding body and helping to avoid curdling. She credits Marjorie Standish, author of Cooking Down East with the idea.
A reasonably good thickener for certain soups--especially Middle Eastern.
"Yoghurt is very good for the stomack, the lumbar regions, appendicitis and apotheosis." --Eugene Ionesco
"Mrs. Beaver stood with her back to the fire, eating her morning yogurt. She held the carton close to her chin and gobbled with a spoon.... 'Heavens, how nasty this stuff is. I wish you'd take to it, John...." --Evelyn Waugh
FoodTale: Note that yoghurt has an undeservedly high reputation in health-food circles. At the turn of the 20th century, it was discovered that the growth of harmful microbes was suppressed in cows by the lactobacilli (found in yoghurt) populating their intestines. An assumption was made...but, unfortunately, lactobacillus bulgaricus does not survive in humans.