Suero Costeño

Suero costeño is the fermented sour cream of Colombia's Caribbean coast, as fundamental to coastal cooking as ají is to the Andes. It is made by leaving fresh milk or cream in a warm place for 24 to 48 hours, the natural lactic acid bacteria fermenting the lactose into lactic acid, producing a tangy, slightly thick, pourable sour cream. Used as a condiment over arepas, arepas de huevo, soups, stews and rice, suero costeño adds acidity and richness. The most famous brand, Pasteurizadora Alpina's suero, is sold in small plastic cups in every store along the coast, and Colombians from the interior consider it a cultural marker of coastal identity. Homemade versions are superior, the fermentation longer and the flavour sharper.

Tangy, creamy and slightly liquid, more acidic than standard sour cream, with a clean lactic flavour. Spooned over a hot arepa or stirred into soup, it adds a bright, cooling acidity.

The technique is natural fermentation. Whole milk or light cream is placed in a clean glass container, covered loosely, and left at warm room temperature (25 to 30 degrees C) for 24 to 48 hours. The lactic acid bacteria naturally present in the milk (or added as a starter from a previous batch) ferment the lactose, producing lactic acid, which thickens and sours the milk. The result is thinner than commercial sour cream, with a sharper acidity. No rennet or cultures are added; the fermentation relies on wild bacteria. The warmer the temperature, the faster the fermentation.