475
Chapter 36
Control by Low pH
and organic Acids
introduction
During the early stages of human history when food was scarce, our ancestors probably recognized
that some foods from plant sources, especially fruits, resisted spoilage. Later, they observed that
the fermented foods and beverages prepared from fruits, vegetables, milk, fish, and meat were
much more shelf stable than the raw materials from which they were produced. That probably
provided an incentive to develop large varieties of fermented foods, especially in tropical areas
where, unless preserved, many foods spoil rapidly. 1
When the microbial involvement in food spoilage and foodborne diseases was recognized,
methods to control their growth as well as to kill them in food were studied. It was observed
that over a restricted pH range, many microorganisms present in food can grow, but at lower pH
ranges many of them die. Once this was recognized, many organic acids were used as food additives. In addition to their effectiveness as food preservatives, they are also used to improve the
acceptance qualities of foods. The amounts and types of organic acids that can be added to foods
are governed by regulatory agencies.
Organic acids can be present in foods in three ways. They can be present naturally, such as
citric acid in citrus fruits, benzoic acid in cranberries, and sorbic acid in rowan berries. Some,
such as acetic, lactic, and propionic acids, are produced in different fermented foods by desirable
food-grade starter-culture bacteria as fermentation byproducts. Many acids are also added to foods
and beverages to reduce the pH. Among the organic acids used in food as preservatives are acetic,
propionic, lactic, citric, sorbic, and benzoic acids; their salts; and some derivatives of benzoic acid
(e.g., paraben). The influence of these acids in reducing food pH and producing antimicrobial
effects are briefly discussed in this chapter.
Chapter 36
Control by Low pH
and organic Acids
introduction
During the early stages of human history when food was scarce, our ancestors probably recognized
that some foods from plant sources, especially fruits, resisted spoilage. Later, they observed that
the fermented foods and beverages prepared from fruits, vegetables, milk, fish, and meat were
much more shelf stable than the raw materials from which they were produced. That probably
provided an incentive to develop large varieties of fermented foods, especially in tropical areas
where, unless preserved, many foods spoil rapidly. 1
When the microbial involvement in food spoilage and foodborne diseases was recognized,
methods to control their growth as well as to kill them in food were studied. It was observed
that over a restricted pH range, many microorganisms present in food can grow, but at lower pH
ranges many of them die. Once this was recognized, many organic acids were used as food additives. In addition to their effectiveness as food preservatives, they are also used to improve the
acceptance qualities of foods. The amounts and types of organic acids that can be added to foods
are governed by regulatory agencies.
Organic acids can be present in foods in three ways. They can be present naturally, such as
citric acid in citrus fruits, benzoic acid in cranberries, and sorbic acid in rowan berries. Some,
such as acetic, lactic, and propionic acids, are produced in different fermented foods by desirable
food-grade starter-culture bacteria as fermentation byproducts. Many acids are also added to foods
and beverages to reduce the pH. Among the organic acids used in food as preservatives are acetic,
propionic, lactic, citric, sorbic, and benzoic acids; their salts; and some derivatives of benzoic acid
(e.g., paraben). The influence of these acids in reducing food pH and producing antimicrobial
effects are briefly discussed in this chapter.