The pH Scale
Importance of the pH Level
In people, serious illness or death can occur when their pH falls or rises abnormally. The pH of human blood is normally between 7.35 and 7.45. Acidosis occurs when the pH of the blood falls while alkalosis results when the pH of the blood goes up. Heart and kidney failure, diabetes, and persistent diarrhea can lead to a condition of acidosis. Alkalosis, on the other hand, may occur as a result of overbreathing caused by anxiety, hysteria, or exposure to high places.
At times, the pH of saliva is greater than 7. This means saliva is basic and can neutralize the acid in the mouth.
The pH of human tears is at 7.4. Shampoos for infants and children are formulated at this pH level. This is the reason why baby shampoos do not cause irritation even when they get into the eyes of infants and children. Generally, shampoos for adults have a pH between 4 and 6. A value higher than this will cause dryness and splitting of hair. Hair is made up of protein molecules called keratin. These molecules are held together by a bond that will break at a higher pH. Hair remover solutions have a pH of 12.
Controlling the pH is also very important in the production of wine, vinegar, cheese, and tomato ketchup. For one, cheese and wine taste well because their pH is maintained at a certain level.
The pH also plays an important role in controlling the growth of microorganisms such as in the case of food spoilage. Most bacteria grow in an environment with a pH of 6.5 to 7.5. Microorganisms like molds prefer neutral to slightly acidic conditions, while yeasts can grow at a pH range of 4 to 6. Generally, however, bacteria cannot survive in an acidic medium. This means that at a lower pH, food can last long and will not spoil easily. For example, tomato ketchup does not develop molds when it is properly stored to maintain its pH at a low level.
Vinegar, which has a pH level of 3, is widely used in food preparation to prevent food spoilage and prolong the shelf life of food items.
