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• Use the pH scale to determine the acidity of a food
• Know the approximate PH of selected foods.
• Determine the PH of selected foods.
• Comprehend that PH affects the quality of foods.

Type of acid varies from food to food. Some acids found in foods are: acetic, lactic, malic, and succinic. The acids present in the foods contribute to the pH range. The more acids the lower the pH is likely to be.

The pH values shown are only approximate. The only way to truly know the pH of a food is to measure it following acceptable procedures. If one reviews the values that are presented in the Food Resource, it is apparent that considerable variation exists between varieties, processing methods, and storage and preparation methods of foods. Even a slight difference in pH value may profoundly impact color, texture or flavor of a food item.

Foods	Approximate pH of Foods
limes	1.9
lemons	2.1
apples	3.1
apple juice	4.0
tomato juice	4.4
buttermilk	4.5
bananas	4.6
Cheddar Cheese	5.3
beef	5.5
cabbage	5.7
asparagus	5.9
milk	6.4
crab	7.0
egg white	8.0

	One simple, crude method of determining if a food is acidic is to taste it. A sour or acidic taste is a positive indicator. Bear in mind, however, that the accuracy of this measure is highly subjective, as sensitivity varies between individuals, and training in sensory evaluation increases one's sensitivity.
	Another crude method is to add cranberry juice. Cranberries and other anthocyanin-containing berries and fruit juices become redder in acid medium and bluer in alkaline medium.
	Indicator paper is a more precise method of evaluating the pH of foods. Indicator paper is a specially treated strip of paper which turns color when placed in a food and can then be compared to reference colors with pH values assigned to them.
	Finally, a pH analyzer may be used. These are generally standardized and measure the H+ concentration. Such a determination is then converted to a pH value.

PH, or the amount of acid or base, can affect the actual color, texture and flavor of foods. For example, what is the difference between a sour versus sweet apple? Generally, it is the amount and types of acids. The acids will make something more sour and "acidity". Pigments are usually affected by the pH. They may change hue (color) or value (darkness or lightness). Finally, texture makes a difference. Egg foams may be more stable with added acid. A milk gel may be formed with added acid. The toughness of baked product structure may be affected by acid.

GLOSSARY

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acid
acidulate
algorithm
alkali
amphiphilic
amphoteric elements
anion
base
buffer
butyric acid
caproic acid
cation
fatty acid
food safety
galacturonic acid
linoleic acid
linolenic acid
organic acid
oxalic acid
pH
saturated fatty acid