Preservatives

Food Toxicology 2(2+0)
Lesson 21 : Food Additives, Colors, and Flavors

Preservatives

This is a group of substances added to food to keep them edible for an extended period of time, usually by preventing the growth of bacteria and fungi. Overall, preservatives are harmless at the levels ingested and beneficial for their ability to reduce or prevent the risks due to microorganism contamination.

  • Benzoic acid and sodium benzoate
    They are found at concentrations of 0.05 to 0.1% in beverages, fruit salads, jams and jellies, preserves, margarine, various relishes, pies, soy sauce, etc. The LD 50 in rodents is 2700 mg/kg. The symptoms of toxicity include weight loss, diarrhea, internal bleeding, enlargement of the liver and kidney, hypersensitivity, and paralysis followed by death.

  • Sorbate
    Sorbates have been used as preservatives in margarine, fish, cheese, bread, and cake. When dissolved in water, potassium sorbate ionizes to form sorbic acid, which is effective against yeasts, molds, and selective bacteria, and is widely used at 250 to 1000 ppm in cheeses, dips, yogurt, sour cream, bread, cakes, pies and fillings, baking mixes, dough, icing, fudges, toppings, beverages, margarine, salads, fermented and acidified vegetables, olives, fruit products, dressings, smoked and salted fish, confections, and mayonnaise. LD 50= 10.5 g/kg).

  • Hydrogen peroxide
    This compound has been used in the dairy industry as a substitute for heat pasteurization. It has also been used for its bleaching effect in cheese and fish-paste products. The LD50 in rats is 700 mg/kg.

  • Nitrite and nitrate
    These substances prevent growth of C. botulinum , the bacterium responsible for the highly potent botulinum toxin. However, a decrease in the incidence of botulism may be accompanied by increase in the formation of carcinogenic nitrosamines in meat products containing nitrite or nitrate. In addition to carcinogenic effects, nitrites and nitrates reduced by bacteria to nitrites can oxidize hemoglobin to methemoglobin. Methemoglobin poorly binds to oxygen and leads to a state of anoxia, which can be life threatening, particularly to children.

  • Antioxidants
    These substances are important because they are used to protect oils and fats against lipid peroxidation or oxidative rancidity. Foods rich in lipids and polyunsaturated fatty acids are extremely sensitive to oxidation, which results in changes of color, odor, taste, and nutritional value.Vitamin C in high levels and in the presence of metals such as iron and copper can cause oxidative damage.

  • Tocopherol
    It is crucial in protecting unsaturated fatty acids from oxidative breakdown and preventing rancidity. The toxicity is low, but high concentrations (>2000 ppm) in oils promote prooxidant effects, particularly if metal ions are present.

  • Propyl gallate
    Propyl gallate, or n -propyl-3,4,5-trihydroxybenzoate, is used as an antioxidant in vegetable oils and butter. The bitter taste restricts its use in some foods.

  • BHT AND BHA
    Butylated hydroxyanisole (BHA) and butylated hydroxytoluene are very commonly used antioxidants in the food industry. Both are GRAS substances, limited by a total antioxidant content of not more than 0.02% of the oil or fat content of the food. They are also found as additives in dry cereals, shortenings, potato products, dessert mixes, and in beverages and desserts made from dry mixes.

  • BHT prevents degenerative oxidation of fats, which can lead to off-flavor and destruction of essential fatty acids and lipid-soluble vitamins. It also prevents the formation of toxic oxidation by-products. BHT was tested in the National Cancer Institute‚Äôs Carcinogenesis Testing Program, which concluded that BHT was not carcinogenic for rats or mice.

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Last modified: Friday, 24 February 2012, 6:46 AM