中文摘要：

以光明牌系列鲜牛奶为研究对象,选取蛋白质含量和钙含量作为测定对象,以考马斯亮蓝G-250与牛奶中的蛋白质形成蓝色的复合物,该复合物在595 nm处光密度与浓度呈线性关系的方法测定了牛奶中蛋白质含量;以草酸钠和牛奶中的钙离子形成沉淀,沉淀酸溶后高锰酸钾滴定草酸根含量的方法间接测定了牛奶中钙的含量;然后计算每元钱购买的牛奶中蛋白质含量和钙含量。实验结果表明,仅从购买蛋白质的性价比考虑,纯牛奶（4.31 g/元）〉优加纯牛奶（4.05 g/元）〉高钙奶（3.94 g/元）〉优加低脂奶（2.82 g/元）〉优倍纯牛奶（2.19 g/元）;仅从购买钙的性价比考虑,高钙奶（123.62 mg/元）〉纯牛奶（111.40 mg/元）〉优加纯牛奶（92.30 mg/元）〉优加低脂奶（78.03 mg/元）〉优倍纯牛奶（50.56mg/元）。综合2种因素考虑,光明系列牛奶中纯牛奶性价比最高,高钙奶和优加纯牛奶性价较高,没有特殊需求时购买纯牛奶最合算。

英文摘要：

Guangming milk was chosen as research object and protein content and calcium content were selected to evaluate the quality of milk. Coomassie brilliant blue G-250 and protein can form blue complex, whose 595 nm absorbance is strictly linear with protein concentration. By using Na2C2O4 to precipitate the Ca^2＋ in the milk, and then using KMnO4 to measure the C2O4^2- after dissolving the precipitation with sulfuric acid, the calcium content of the milk was determinated; then how much protein and calcium per yuan was calculated. The results show when the protein cost performance was considered, pure milk（4.31 g/yuan） 〉 Youjia pure milk （4.05 g/yuan） 〉 high calcium milk （3.94 g/ yuan） 〉 Youjia low fat milk（2.82 g/yuan） 〉 Youbei pure milk（2.19 g/yuan）and when the calcium cost performance was considered, high calcium milk（ 123.62 mg/yuan） 〉 pure milk（ 111.40 mg/yuan） 〉 Youjia pure milk（92.30 rag/ yuan） 〉 Youjia low fat milk（78.03 mg/yuan） 〉 Youbei pure milk（50.56 mg/yuan）. If the two indexes were considered at the same time, Guangming pure milk had the highest cost performance, and high calcium milk and Youjia pure milk had a higher cost performance. Therefore, when there is no special need, Guangming pure milk is the best choice.