What acidification means
Acidification is the process of making a food more acidic. It happens in different ways that cooks meet regularly. One is by adding an acid directly, such as vinegar in pickles or citric acid in jams. Another is through fermentation, where bacteria feed on sugars and produce acids, mainly lactic acid.
This is what happens in yoghurt, cheese, sourdough, sauerkraut, kimchi and traditional fermented pickles. Acidification changes food in several ways. It gives a sharp, tangy flavour, and it changes texture, which is why milk thickens into yoghurt and curds form when cheese is made. In cheesemaking, the speed and degree of acidification help decide whether a cheese ends up soft and fresh or firm and aged, so cheesemakers control it carefully with starter cultures, temperature and time.
In bread, the gradual acidification of a sourdough starter gives the loaf its characteristic sour taste and affects how the dough behaves. Acid is also part of how pickles and some preserves develop their character. The word is more technical than most kitchen vocabulary, so you will usually see it in cheesemaking guides, fermentation books, food science writing and baking manuals rather than in everyday recipes.