Acids and Bases (Acidity and Alkalinity)

1. Acids and Bases(Acidity and Alkalinity)

2. Acidity • Have more hydrogen ions (H+) • Make foods acid • Examples include: • Lemon juice • Vinegar • Other characteristics of acidic foods: • Sour taste • Sting when touched • React strongly when combined with metals A 2.02 -- Acids and Bases

3. Bases /Alkalinity • Have more hydroxide ions (OH) • Makes foods more alkaline • Examples include: • Soap • Egg whites • Other characteristics of a alkaline: • Bitter taste • Feel slippery to touch • Do not react when combined with metals A 2.02 -- Acids and Bases

4. ACIDS Taste sour Turn red when tested pH between 0 and 6.9 BASES Taste bitter Turn blue when teted pH between 7.1 and 14 Acids and Bases identified by: A 2.02 -- Acids and Bases

5. Effects of pH on food • pH is a measure of acidity or alkalinity of food. • Changes in pH effect quality. • Color • Texture • Stability • Changes in pH effect safety • Foods are generally acidic (pH less than 7.0) • Low acid foods have a pH between 4.6 and 7.0 (potentially hazardous food) • High acid foods have a pH of 4.6 or less. (non-potentially hazardous food) A 2.02 -- Acids and Bases

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7. pH Measurement Methods for Reliable and Accurate Measures of pH

8. Definition of pH • A way to measure acids (acidic) and bases (alkalinity) in food. • Expression of the concentration of hydrogen (H+) and hydroxide ions (OH-) in an aqueous solution (water-based). • Uses a scale between 0 and 14 A 2.02 -- Acids and Bases

9. Measurement Method– Litmus Paper 1. Used by dipping litmus paper into solution 2. Turns yellow to red in acidic solution (acid) 3. Turns green or blue in alkaline solution (base) 4. Easy method 5. Not completely accurate A 2.02 -- Acids and Bases

10. Measurement Method – Indicator Strips • Dip the strip into the aqueous (liquid) food being tested for a few seconds. • Remove strip from test solution and compare color segments to center color printed on the strip. A 2.02 -- Acids and Bases

11. Measurement Method – Indicator Dye • Organic dyes • Done with dropper • Acidic (acid) -- pink or red • Alkaline (base) -- green or blue • Neutral solution may turn lilac • Not totally accurate A 2.02 -- Acids and Bases

12. Measurement Method – pH Meter • Digital reading • Accurate • Some units are expensive • Easy and sanitary A 2.02 -- Acids and Bases

13. Measure Method – Titratable Acidity 1. Add base with know pH to an acid. 2. Use burette. 3. More difficult to calculate. 4. Use if have chemistry knowledge. A 2.02 -- Acids and Bases

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15. Chemical Properties Of Food A 2.02 -- Acids and Bases

16. Chemical Properties • pH – measure of acidity and alkalinity • Total solids -- total content of suspended and dissolved solids in water • Ash -- mineral content of the food • Titratable acidity -- approximation of a solution's total acidity • Total sugars– approximation of all carbohydrates • Total fatty acids A 2.02 -- Acids and Bases

17. Chemical Changes • Occurs whenever new substances with different chemical and physical properties are formed. • Chemical changes result in: • Changes in color– enzymatic browning, carmelization of sugar • Changes in odor– cooked cabbage smell • Flavor changes– cooked onions, fermented foods. • Release of gas– mixing baking soda and vinegar, alcoholic beverages A 2.02 -- Acids and Bases