Cultured dairy products is an alternative term for fermented dairy products: milks, creams and related foods fermented by selected lactic acid bacteria, including yoghurt, kefir, cultured buttermilk and sour cream. Fermentation converts lactose to lactic acid, creating tangy flavour, thicker texture and a lower pH that extends shelf life and suppresses pathogens. Quality control centres on starter culture performance, fermentation time and temperature, and rapid post-production cooling to keep acidity and texture stable through distribution. Starter strains are chosen for reliable acid production and clean flavour, and plants verify culture activity daily so fermentation stays on schedule.