Food Additives - Sulfites and Your Health
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What is Enzymatic and Nonenzymatic Browning?
Enzymatic browning is the discoloration that results when monophenolic compounds in plants or shellfish react with oxygen and the enzyme polyphenol oxidase (PPO) to form a brown pigment. This is a problem in a number of light-colored foods, specifically apples, pears, peaches, bananas, potatoes, mushrooms, and seafood. This discoloration limits the shelf-life of many minimally processed foods. To prevent this from occurring, sulfites act as enzyme (PPO) inhibitors to prevent brown color formation.Nonenzymatic browning produces discoloration through the "Maillard reaction." The Maillard reaction occurs when sugars react with free amino groups in proteins, producing a brown pigment. This color change limits the shelf-life of various dehydrated fruits and vegetables, citrus products, and juices. Sulfites inhibit nonenzymatic browning by reacting with carbonyl intermediates, thereby preventing their further reaction to form brown pigments (Wedzicha, 1987).
Sulfite Sensitivity
A small percentage of the population appears to be sensitive to sulfites, particularly those with asthma. In 1982, the FDA received reports of adverse allergic-type reactions that were attributed to the consumption of foods containing sulfites. These reports indicated that sulfites can induce asthmatic episodes in an estimated 5 to 10 percent of the asthmatic population. The symptom most reported is difficulty breathing. Other problems range from stomach ache to hives to anaphylactic shock (Taylor et al., 1986).As a result of these problems, FDA requested the Federation of American Societies for Experimental Biology (FASEB) to re-examine the use of sulfites. From the study, FASEB estimated that more than one million asthmatics are sensitive or allergic to the substance. They also concluded that sulfiting agents are not teratogenic, mutagenic, or carcinogenic in laboratory animals. Sulfites are readily metabolized in the body by pathways that normally break down other sources of sulfur in the diet, such as sulfur-containing amino acids like methionine. They concluded that "for the majority of the population, there is no evidence...that demonstrates or suggests reasonable grounds to suspect a hazard to the public when these substances are used at levels that are now current" (FASEB, 1985). In August 1986, the FDA prohibited the use of sulfites in fresh fruits and vegetables such as those found on produce counters in the market and those served in restaurant salad bars. The use of sulfites on fresh fruits and vegetables was banned because sensitive individuals could not be warned of high levels of sulfite. By January 1987, packaged foods containing sulfiting agents at greater than 10 ppm were required to indicate as such on the label. By labeling high-sulfite foods, the benefits remain for most consumers while the risk is minimized for sensitive individuals.
Precautions for Sulfite Sensitive Individuals
People who are sulfite-sensitive should know those foods that may possibly contain sulfites. But it is not always obvious by the chemical names on the label those ingredients that are sulfites. Currently, there are six sulfiting agents allowed in packaged foods. These are: | sulfur dioxide | sodium sulfite | sodium and potassium bisulfite | sodium and potassium metabisulfite | |
Sulfite is used typically in the following foods:
| baked goods | processed seafood | beer | frozen shrimp/lobster | wine | gelatin | tea | grain products | condiments | nut products | vinegar | dried fruits | dairy products | fruit juices | dehydrated vegetables | soup mixes | dehydrated potatoes | filled crackers | canned vegetables | plant protein isolates | frozen potatoes | molasses | vegetable juice | sweet sauces | |
The following suggestions are helpful for sulfite-sensitive people:
| Read food labels and choose foods that do not contain sulfites.
Be aware that foods served in restaurants, especially potato products and some canned foods, could contain sulfites. For example, avoid bottled lemon juice because it can be a source of sulfites. Freshly squeezed lemons do not contain sulfites. | |
Sulfite in Foods
Sulfite levels in foods are conventionally expressed as sulfur dioxide, ranging from zero to approximately 3,000 ppm on a dry weight basis. Light-colored dehydrated fruits such as apples, apricots, bleached raisins, pears, and peaches contain the greatest amount of sulfite. Dehydrated vegetables and prepared soup mixes range from a few hundred to 2000 ppm (instant potatoes average about 400 ppm). A range for wines is about 100 to 400 ppm, with beer containing 2 to 8 ppm. Some loss of sulfite occurs during food storage, either through oxidation by air to sulfate or through volatilization or evaporation. Even larger losses occur during cooking.Sulfite Consumption
It is hard to estimate the daily intake of sulfite in the human diet due to lack of reliable information on diets and the wide variation in individual food consumption patterns. The most commonly used figure for daily intake from foods and non-alcoholic beverages in the United States is approximately 2 mg of sulfite per person per day. An additional 5 mg of sulfite per day can be added for wine and beer consumption. The Acceptable Daily Intake (ADI) of sulfites for adults is 0.70 mg per kilogram of body weight, equivalent to 50 mg of sulfite per day for a 70 kg (155 lb) person.Works Cited
FASEB. 1985. The reexamination of the GRAS status of sulfiting agents. Select committee on GRAS substances. Life Sciences Research Office, Federation of American Societies for Experimental Biology. Prepared under FDA contract 223-83-2020, Jan 28.FDA. 1986. Sulfiting Agents: Revocation of GRAS status for use on fruits and vegetables intended to be served or sold raw to consumers. Food and Drug Admin., Fed. Reg. 51:25021- 25026.
FDA. 1987. Sulfiting agents: Proposal to revoke GRAS status for use on "fresh" potatoes served or sold unpackaged and unlabeled to consumers. Food and Drug Admin., Fed. Reg. 52:46968-46978.
This page was updated on March 22, 2006
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