Sour foods

Yogurt (; , from , ; also spelled yoghurt, yogourt or yoghourt) is a food produced by bacterial fermentation of milk. Fermentation of sugars in the milk by these bacteria produces lactic acid, which acts on milk protein to give yogurt its texture and characteristic tart flavor. Cow's milk is most commonly used to make yogurt. Milk from water buffalo, goats, ewes, mares, camels, and yaks is also used to produce yogurt. The milk used may be homogenized or not. It may be pasteurized or raw. Each type of milk produces substantially different results.

Sorrel (Rumex acetosa) is a perennial herbaceous plant in the family Polygonaceae. It is also called common sorrel, garden sorrel, spinach dock and narrow-leaved dock ("dock" often used for the genus).

Sauerkraut (; , ) is finely cut raw white cabbage that has been fermented by various lactic acid bacteria. It has a long shelf life and a distinctive sour flavor, both of which result from the lactic acid formed when the bacteria ferment the sugars in the cabbage leaves.

Ayran ( ) is a cold savory yogurt-based beverage that is consumed across Central Asia, the Balkans, and the Middle East. The principal ingredients are yogurt, water and salt. Herbs such as mint may be optionally added. Some varieties are carbonated. It is a national drink of Turkey.

thumb|Homemade kefir and kvass served alongside kolach and [[korovai]]

Sumac or sumach ( , )—not to be confused with poison sumac—is any of the roughly 35 species of flowering plants in the genus Rhus (and related genera) of the cashew and mango tree family, Anacardiaceae. However, it is Rhus coriaria that is most commonly used for culinary purposes. Sumac is prized as a spice—especially in Arab cuisine, and other Eastern cuisines—and used as a dye and holistic remedy. The plants grow in subtropical and temperate regions, on nearly every continent except Antarctica and South America. It holds cultural significance as a symbolic item on the Haft-sin table during N

sauce

dairy product produced by fermenting a regular cream with certain kinds of lactic acid bacteria

soft, mild-tasting cheese with a high fat content

Umeboshi (Japanese: 梅干し, pronounced , ) are pickled (brined) ume fruits common in Japan. The word umeboshi is often translated into English as 'salted Japanese plums', 'Japanese plums' or 'preserved plums'. Ume (Prunus mume) is a species of fruit-bearing tree in the genus Prunus, which is often called a "plum", but is actually more closely related to the apricot. Pickled ume which are not dried are called umezuke (梅漬け).

Tkemali () is a Georgian sauce primarily made of cherry plum; alucha plum and red-leaf plum are also common plum species used to make Tkemali in Georgia. While the sauce is typically red, both red and green varieties of these plums may be used.

thumb|250px|Picking green grapes for making verjuice. Tacuinum Sanitatis (1474). Paris, Bibliothèque nationale. Verjuice is a highly acidic juice made by pressing unripe grapes, crab-apples or other sour fruit. Sometimes lemon or sorrel juice, herbs or spices are added to change the flavor. It also goes by the name verjus.

Ryazhenka or ryazhanka (; ; ), is a traditional fermented milk product in Ukraine, Russia, and Belarus. It is made from baked milk by lactic acid fermentation.

dairy food that has been fermented with lactic acid bacteria

Doogh () is a cold and savoury Persian drink. It is made with fermented milk. Unlike its sister beverage of Turkish origin, ayran, Doogh is not diluted yogurt. According to the Iranian Ministry of Food Standards, Doogh "is a drink resulting from lactic fermentation of milk whose dry matter is standardized by diluting yogurt (after fermentation) or buttermilk (before fermentation)."

Amchoor (, ), also aamchur, amchur or mango powder, is a fruity spice powder made from dried unripe green mangoes. A citrusy seasoning, it is mostly produced in India. In addition to its use as a seasoning it adds the nutritional benefits of mangoes when the fresh fruit is out of season. thumb|Dried mango slices

thumb| Acidophiline (Russian: ацидофилин) is a type of drinkable yogurt, with Lactobacillus acidophilus as the starter culture. Kefir yeast is also added sometimes. It has antibacterial properties and is used in the former Soviet Bloc countries to treat intestinal diseases such as colitis and enterocolitis. The sweetened acidophiline was widely produced in the USSR, among other fermented milk drinks, such as kefir and ryazhenka.

species of plant

type of ayran