Overview

Yogurt (also spelled yoghurt) is a food made by the controlled fermentation of milk by specific bacteria. During fermentation (fermentation), the milk sugar lactose is converted to lactic acid, which lowers the pH and causes milk proteins to coagulate and produce the characteristic thick texture and tangy flavor. The process is distinct from cheese-making, where curd formation and whey separation create a different texture (curd).

Production and common methods

Commercial and home production follow similar basic steps: heat the milk to near boiling to reduce unwanted microbes and to denature proteins, typically to around 80 °C; cool it to an incubation temperature (commonly near 45 °C); add a starter culture of beneficial bacteria; and hold the mix warm for several hours while fermentation proceeds. Fermentation time and temperature determine firmness and tartness. Modern plants may standardize fat and solids and use mechanical agitation, whereas traditional methods rely on natural thickening.

Varieties and plant-based alternatives

Yogurt comes in many styles: spoonable set yogurts, stirred or pot yogurts, strained forms (often called Greek yogurt) that have whey removed to concentrate protein and texture, and drinkable yogurts. Fermented milk also appears in regional forms such as labneh, ayran and skyr. In addition to dairy, cultured products are made from plant milks such as almond milk, soy milk and coconut milk, using similar bacterial cultures or specialized starters to achieve a comparable texture and flavor.

Nutrition and perceived health effects

Yogurt is valued for its nutrient density: it supplies protein (from the milk proteins), calcium for bone health, and B vitamins including riboflavin, vitamin B6 and vitamin B12. The live bacteria in many yogurts are associated with digestion and are marketed as probiotics, though the strength of clinical benefits varies and depends on strain and dose. Flavored and sweetened commercial yogurts can be high in added sugars, so plain or lightly sweetened options are often recommended for nutrient balance.

Uses, culinary roles and cultural history

Yogurt has a long history as a preserved dairy product used worldwide. Historical accounts attribute early dairy fermentation to pastoral communities who discovered thickened, sour milk as a stable food without refrigeration. Today yogurt is used as a breakfast food, ingredient and condiment: it can be eaten alone, mixed with fruit or granola, thinned into smoothies and sauces, used as a base for dressings, or strained into cheeses like labneh. Typical culinary examples include cucumber raita, Middle Eastern labneh, Mediterranean tzatziki, and Northern European skyr.

Distinctions and practical notes

Yogurt differs from other cultured dairy products by its required cultures and by texture: for instance, kefir is a fermented beverage produced with a broader mix of yeasts and bacteria and is typically effervescent; sour cream is made from cream rather than milk and has higher fat. Regulations on what can be labeled "yogurt" vary by country and may specify minimum live culture content or permitted additives. Refrigeration slows fermentation and preserves quality; unopened commercial yogurts usually last several weeks under proper storage.

  • Key production elements: milk heat treatment, starter culture, controlled incubation.
  • Common forms: set, stirred, strained (Greek), drinkable, plant-based.
  • Typical nutrients: protein, calcium, riboflavin, B6, B12; variable sugar content.

For general background and technical guidance on production, food safety and cultural varieties, see sources linked in the text: milk, bacteria, fermentation, lactose, lactic acid, protein, curd, soy milk, coconut milk, calcium, riboflavin, vitamin B6 and vitamin B12.