To make cultured buttermilk, pasteurized or ultrapasteurized skim or lowfat milk is cultured chiefly with Streptococcus lactis for acid and flavor and incubated at 20° to 22°C until the acidity is 0.8% to 0.9% (pH 4.6). In contrast, sweet cream buttermilk is the by-product of churning cream into butter. Fluid buttermilk sold on the retail level is generally cultured. Both varieties are available in dry form for the food industry.