Acidity in milk 1) Apparent acidity:derived from the alkali binding properties of casein phosphates,citrates and CO2. Usually it is between 0.15%-0.18%.(lactic acid) 2)Developed acidity:results from the fermentation of milk by lactic acid bacteria.When it is above 0.2%, lactic acid exists. 3)Two ways to express acidity in milk T:the volume of 0.1000mol/l NaOH depleted by 100ml milk sample.The apparent acidity of fresh milk is 16-18 0T the acidity in the milk can be expressed by lactic acid percentage
• Acidity in milk 1) Apparent acidity: derived from the alkali binding properties of casein , phosphates,citrates and CO2. Usually it is between 0.15%-0.18%. (% lactic acid) 2) Developed acidity:results from the fermentation of milk by lactic acid bacteria. When it is above 0.2%, lactic acid exists. 3) Two ways to express acidity in milk 0T: the volume of 0.1000mol/l NaOH depleted by 100ml milk sample. The apparent acidity of fresh milk is 16-18 0T the acidity in the milk can be expressed by lactic acid percentage
Effects of acids in food process 1)Color change 2)Food taste 3)Food stability 4)Maturity of fruits 5)Standards of food quality such as:stale oil,meat(PH升高，大于6.7则腐 败)；rotten fruits
Effects of acids in food process 1)Color change 2) Food taste 3)Food stability 4) Maturity of fruits 5) Standards of food quality such as: stale oil, meat(PH升高，大于6.7则腐 败）; rotten fruits
Source and distribution of organic acid Malic acid,citric acid, Acid salt organic acid tartaric acid,oxalic acid, lactic acid,succinic acid, acetic acid,etc Acid in food neutral salt Distribution of organic acid is shown in the text
Source and distribution of organic acid Acid in food organic acid inorganic acid Malic acid, citric acid, tartaric acid,oxalic acid, lactic acid,succinic acid, acetic acid, etc. neutral salt Free state Acid salt Distribution of organic acid is shown in the text
Determination of acidity 1)Determination of total acidity 2)Determination of effective acidity 3)Determination of volatile acidity
Determination of acidity 1)Determination of total acidity 2)Determination of effective acidity 3)Determination of volatile acidity
Determination of total acidity Principle:an acid-base titration RCOOH+NaOH-RCOONa +H2O 食品中的有机酸（弱酸）用标准碱液滴定时，被中和生成盐 类。用酚酞作指示剂，当滴定到终点（pH=8.2,指示剂显 红色)时，根据消耗的标准碱液体积，计算出样品总酸的 含量
Determination of total acidity Principle: an acid-base titration RCOOH + NaOH→ RCOONa +H2O 食品中的有机酸（弱酸）用标准碱液滴定时，被中和生成盐 类。用酚酞作指示剂，当滴定到终点（pH=8.2,指示剂显 红色）时，根据消耗的标准碱液体积，计算出样品总酸的 含量