Potassium Bisulphite as a Food Preservative

Preservatives are a food safety measure used to prolong shelf life and keep foods from spoiling. Potassium bisulphite is a food additive that inhibits the growth of bacteria, mold and yeast, and it helps prevent food discoloration. Some people may need to avoid any food that contains this particular additive, however.

About Potassium Bisulphite

Potassium bisulphite, also spelled "bisulfite," is sometimes referred to as a sulfite salt; it falls into the same category of food additives such as sodium sulfite, potassium sulfite and sodium bisulfite. Potassium bisulphite is a white powder that dissolves in water but not in alcohol. Unlike other sulfur salts such as sodium sulfite, potassium bisulphite has a sulfur smell. It is considered a legal food additive in the United States, according to Thomas E. Furia, author of "CRC Handbook of Food Additives, Second Edition, Volume 1."

How It Works

When potassium bisulphite is dissolved in water, it forms a sulfurous acid. The acid lowers the pH of the food, which helps inhibit the growth of harmful organisms, including bacteria such as E. coli, as well as yeast and mold. The bisulphite also prevents browning or discoloration of food Potassium bisulphite is more stable than potassium sulfite. In humid conditions, however, the dry salt may oxidize and lose some of its antimicrobial power.

Food Sources

Sulfite food additives such as potassium bisulphite are most often found in wine. But you may also find potassium bisulphite in dried fruit -- such as apricots and peaches -- and it's often found in dehydrated vegetables, such as potatoes and carrots. It may also be used as a preservative in cut fruit, such as apples, to prevent browning.

Safety Concerns

People with sulphite sensitivity might react poorly to potassium bisulphite. A sulphite sensitivity usually causes asthma symptoms such as wheezing or difficulty breathing. Some people may also experience anaphylaxis, which is a life-threatening allergic reaction. If you have a sensitivity to sulphites, you should avoid any food that contains potassium bisulphite.