河南科技学院：《食品分析》课程教学课件（PPT讲稿）Chapter 7 Determination of acidity

Chapter 7. Determination of acidity

Chapter 7. Determination of acidity

Section 1. General

Section 1. General

1. Concept of acidity • 1. Total acidity • 2. Effective acidity • 3. Volatile acid • 4. Acidity of milk

1. Concept of acidity • 1. Total acidity • 2. Effective acidity • 3. Volatile acid • 4. Acidity of milk

2. Significance of acidity • Organic acid affects color, aroma, taste and stability of foods. • Quality of foods can be judged by acidity. • Mature degree of some fruits can be judged by acidity

2. Significance of acidity • Organic acid affects color, aroma, taste and stability of foods. • Quality of foods can be judged by acidity. • Mature degree of some fruits can be judged by acidity

3. Organic acid kinds and distribution of foods • There are organic acid and inorganic acid in foods, and mainly organic acid. • Familiar organic acids in foods: citric acid, malic acid, tartaric acid, oxalic acid, lactic acid and acetic acid

3. Organic acid kinds and distribution of foods • There are organic acid and inorganic acid in foods, and mainly organic acid. • Familiar organic acids in foods: citric acid, malic acid, tartaric acid, oxalic acid, lactic acid and acetic acid

Section 2. Determination of acidity

Section 2. Determination of acidity

1. Determination of total acidity • 1.1 Principle : RCOOH + NaOH = RCOONa + H2O Indicator: phenolphthalein, PH8.2 • 1.2 Applying range : Foods of slight color

1. Determination of total acidity • 1.1 Principle : RCOOH + NaOH = RCOONa + H2O Indicator: phenolphthalein, PH8.2 • 1.2 Applying range : Foods of slight color

2. Determination of pH • pH test paper • pH meter

2. Determination of pH • pH test paper • pH meter

pH meter

pH meter

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