Acids and Bases (Acidity and Alkalinity). A 2.02 -- Acids and Bases Acidity Have more hydrogen ions...

A 2.02 -- Acids and Bases

Acids and Bases(Acidity and Alkalinity)


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


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


Acids and Bases identified by:

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


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)


pH Measurement

Methods for Reliable and Accurate Measures of pH


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


Measurement Method– Litmus Paper1. Used by dipping litmus

paper into solution2. Turns yellow to red in

acidic solution (acid)3. Turns green or blue in

alkaline solution (base)4. Easy method5. Not completely

accurate


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.


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


Measurement Method – pH Meter

Digital reading Accurate Some units are

expensive Easy and sanitary


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.


Chemical Properties Of Food


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


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

Acids and Bases (Acidity and Alkalinity). A 2.02 -- Acids and Bases Acidity Have more hydrogen ions...

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