Yogurt

Yogurt is an acid gel of Milk. Coagulation puts the contrast in one sentence: cheese keeps a gel you cut so whey can leave; yogurt is a different acid gel you usually do not cut that way. FAO’s cheese notes use yoghurt cultures as mozzarella starters: Lactobacillus bulgaricus and Streptococcus thermophilus, thermophilic strains they describe as growing with optima between 40 and 45 °C ¹. The 2020 lactic-acid-bacteria taxonomy split moved many former Lactobacillus names; the kitchen job is still lactic acid from lactose ². See Lactic acid bacteria and Cheese cultures.

Heat the milk, then hold it warm #

FAO’s yoghurt-culture prep for cheese work: heat the milk to 90–95 °C for 20–30 minutes, cool to 43–45 °C, add the culture, and incubate at 43–45 °C ¹. Those figures are a training procedure for a starter, not a U.S. yogurt identity or a food-safety process. The heat step denatures whey proteins so the later acid gel holds more water — a texture reason, visible as a firmer set than milk soured cold.

Acid coagulation in FAO’s cheese physics is temperature-sensitive: warmer milk can set at a higher pH ¹. That is why yogurt is incubated warm. See Acid-set cheese.

What to notice #

The mass should jiggle as one piece, not look like sweet milk. Whey pooling on top is syneresis — a quality leak, not a second cheese unless you choose to drain it. Smell clean lactic, like the healthy vat on Cheese cultures. A sluggish set is culture, temperature, or milk that still holds antibiotics — FAO: do not use milk with antibiotics ¹.

Composition thinking still applies if you drain yogurt toward a cheese: moisture you keep is moisture you live with ³. Pasta filata hires these same thermophilic cultures for acid, then stretches; that is Pasta filata, not a cup of yogurt. Fermentation is the shared idea.