The present invention provides a sour taste enhancer capable of enhancing sourness by adding to seasoning, food, etc., and a method for enhancing sourness.The sour taste enhancer of the present invention has a peroxide value of 15 to 180, and an oxidized fat and oil content of 10% by mass or more and 100% by mass or less of milk fat as an active ingredient. Also, the sourness of the seasoning and food of the present invention are enhanced by the addition of the sourness enhancer. Furthermore, the method for enhancing sourness of the present invention is a method of enhancing the seasoning and food by adding an oxidized fat and oil having a peroxide value of 15 to 180, and containing 10% by mass or more and 100% by mass or less of milk fat.本發明係提供一種可藉由添加於調味料、食品等而增強酸味的酸味增強劑,以及增強酸味的方法。本發明之酸味增強劑係以過氧化物價為15至180且含有10質量%以上100質量%以下的乳脂之氧化油脂做為有效成分者。又,本發明之調味料及食品係藉由該酸味增強劑的添加而增強酸味。再者,本發明之調味料及食品的酸味的增強方法係藉由過氧化物價為15至180且含有10質量%以上100質量%以下的乳脂之氧化油脂,添加於前述調味料、或食品。