6.2.1: Learning Objectives
After this lab you should be able to:
- Define pH.
- Explain the quantitative difference between two different pH values, for example, pH 4 and pH 6.
- Describe the major effects pH changes can have on a cell.
“Growth of the bacterium Clostridium botulinum in canned food may cause botulism—a deadly form of food poisoning. These bacteria exist either as spores or as vegetative cells. The spores, which are comparable to plant seeds, can survive harmlessly in soil and water for many years. When ideal conditions exist for growth, the spores produce vegetative cells, which multiply rapidly and may produce a deadly toxin within 3 to 4 days of growth.
Acidity may be natural, as in most fruits, or added, as in pickled food. Low-acid canned foods are not acidic enough to prevent the growth of these bacteria. Acid foods contain enough acid to block their growth, or destroy them more rapidly when heated. The term "pH" is a measure of acidity; the lower its value, the more acid the food. The acidity level in foods can be increased by adding lemon juice, citric acid, or vinegar.”
National Center for Home Food Preservation: http://nchfp.uga.edu/how/general/ensuring_safe_canned_foods.htm l