A 2.02 -- Acids and Bases
Acids and Bases(Acidity and Alkalinity)
A 2.02 -- Acids and Bases
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
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
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
A 2.02 -- Acids and Bases
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
A 2.02 -- Acids and Bases
pH Measurement
Methods for Reliable and Accurate Measures of pH
A 2.02 -- Acids and Bases
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
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
A 2.02 -- Acids and Bases
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
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
Measurement Method – pH Meter
Digital reading Accurate Some units are
expensive Easy and sanitary
A 2.02 -- Acids and Bases
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
A 2.02 -- Acids and Bases
Chemical Properties Of Food
A 2.02 -- Acids and Bases
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
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
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