Preservatives
A preservative is a substance that is added to products such as foods, pharmaceuticals, paints, biological samples, cosmetics, tires, wood, beverages, and many other products to prevent decomposition by microbial growth or by undesirable chemical changes
Antioxidants
An antioxidant is a molecule that inhibits the oxidation of other molecules. Oxidation is a chemical reaction that can produce free radicals, leading to chain reactions that may damage cells.
 Antioxidants as Food Preservatives
While commonly regarded for their health benefits, antioxidants are also used as food additives. Antioxidants make an effective guard against food deterioration given that exposure to oxygen and sunlight are the two main factors in oxidation. Food preservatives can include natural antioxidants such as ascorbyl palmitate, tocopherols and tocopherol acetate, as well as synthetic antioxidants such as propyl gallate (PG), tertiary butylhydroquinone (TBHQ), butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and ethoxyquin.
Oxidation profoundly affects the quality of food and shortens its shelf life by adversely affecting its appearance, texture, sensory properties, and nutritive value. All major food components are susceptible to oxidation, resulting in changes in flavor and aroma (lipids), texture and functionality (proteins), and loss of nutritive value (vitamins). In addition, the oxidation of pigments results in degradation of color and visual appeal and diminished product marketability. It is, therefore, extremely important to find effective solutions for prevention of oxidation processes in foods.
Some examples of potent natural antioxidants and their sources include: tocopherols (nuts and seeds), ascorbic and citric acids (citrus fruits), carotenoids (fruits and vegetables) and phenolic compounds (herbs and spices, grape seeds). Plant phenolic extracts are often used in preservation of seafood, meat, fats and oils. Ascorbic acid is used in preservation of juices, cereals, jams, cured meats and some canned foods, while tocopherols found their applications in preservation of cereals, meat and poultry products, butter, oils, and dairy products.
Preservation is the prevention or inhibition of microbial growth. In pharmacy, this is commonly accomplished by the addition of a preservative to a product, with the primary purpose of minimizing microbial growth (as in oral liquids, topical, etc.), or for preventing microbial growth (as in sterile preparations such as parenterals).
Several factors are involved in the selection of a preservative, including concentration, pH, taste, odor and solubility. Some preparations, such as syrups, are inherently preserved by the high concentration of sugar present, which acts as an osmotic preservative.
n most preparations, however, a suitable preservative must be selected and attention paid to assuring preparation of a stable product. A preservative must be nontoxic, stable, compatible and inexpensive and have an acceptable taste, odor and color. It should also be effective against a wide variety of bacteria, fungi and yeasts
Autoxidation is the reaction of any substance with molecular oxygen. These reactions can be catalyzed by heavy metals, especially those with two or more valency states (cobalt, copper, iron, nickel). Other catalysts include hydrogen and hydroxyl ions, since the redox potential of many compounds is pH related. These catalysts can reduce the onset time and increase the rate of autoxidation reactions. The catalysts, in essence, increase the rate of formation of free radicals.
Antioxidants are among a number of adjuvants commonly added to pharmaceutical systems to enhance physical and chemical stability. Antioxidants are added to minimize or retard oxidative processes that occur with some drugs or excipients upon exposure to oxygen or in the presence of free radicals. These processes can often be catalyzed by light, temperature, hydrogen ion concentration, presence of trace metals, or peroxides.
Some substances prone to oxidation include unsaturated oils/fats, compounds with aldehyde or phenolic groups, colors, flavors, sweeteners, plastics and rubbers, the latter being used in containers for products.
