An acidic dairy product having a pH of 3.0 to 5.0 and a lactose content of at least 1.5 mg / mL, comprising lactase, wherein the lactase is at a level of at least 5% compared to its activity at the optimum pH of lactase. A lactase-containing acidic dairy product is provided that retains its pH and its activity at a temperature of 37 ° C. [Selection] Figure 23.0~5.0のpHと少なくとも1.5 mg/mLの乳糖含量を有する酸性乳製品であって、ラクターゼを含有し、該ラクターゼがラクターゼの最適pHでのその活性に比較して少なくとも5%のレベルで5.0のpHと37℃の温度でのその活性を保持する、ラクターゼ含有酸性乳製品が提供される。【選択図】図2