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Info Centre >> Water Treatment Technical Manual >> 4. Applications Related/General Information >> 4.2 Measurement of pH in the Biochemistry and Food Industries


4.2 Measurement of pH in the Biochemistry and Food Industries


Electrochemical measurements using pH meters are now simple and accurate. Micro-electronic components have made possible small portable high quality instruments with digital displays, some with built-in electrodes. These meters measure the potential difference between a glass electrode and a standard calomel electrode or silver/silver chloride electrode and are calibrated by the use of prepared or purchased buffer solutions of accurately known pH. There are also available other types of electrodes designed for special purposes, such as probe electrodes for the examination of carcass meat. Very accurate pH measurement, through seldom required in food analysis, is very susceptible to the temperature of the test solution. Temperature compensation devices are incorporated in pH meters to correct for known temperature deviations.

Some of the pH values of a number of biological materials are given below:

Table A - pH Values of Representative Biological Materials, Elements of Food Biochemistry, William H. Peterson, Ph.D., John T. Skinner, Ph.D. and Frank M. Strong, Ph.D., pg 69

Water Treatment Testing: Food & Beverage

*Information Provided Courtesy of Eutech Instruments Pte Ltd Copyright © 1997


pH Values of Common Substances
Material
pH value
Blood, normal limits 7.3 - 7.5
Blood, extreme limits 7.0 - 7.8
Enzymes, activity range of
Amylopsin, optimum 7.0
Erepsin, optimum 7.8
Invertase, optimum 5.5
Lipase, optimum 7.0 - 8.0
Maltase, optimum 6.1 - 6.8
Pepsin, optimum 1.5 - 2.4
Trypsin, optimum 8.0 - 9.0
Fruit Juices
Apple 3.8
Banana 4.6
Grapefruit 3.0 - 3.3
Orange 3.1 -4.1
Tomato 4.2
Gastric juice (adult) 0.9 - 1.6
Milk (cows) 6.2 - 7.3
Plants (extracted juice)
Alfalfa tops 5.9
Carrot 5.2
Cucumber 5.2
Peas, field 6.8
Potato 6.1
Rhubarb, stalks 3.4
String beans 5.2
Sweat 4.5 - 7.1
Saliva 6.2 - 7.6
Urine (human) 4.2 - 8.0
Tears 7.2