November 5, 2009
by Rebeca López-García, Ph.D.
Nowadays, antioxidants are, perhaps, some of the best recognized health-related molecules. The term antioxidant is used in general to define any substance that delays or inhibits oxidative damage to a target molecule. Within the product itself, antioxidants help maintain product freshness by fighting the rancidity of fats and oils. Antioxidants also act as biologically active materials believed to protect the body from developing chronic diseases and slow down the aging process.
PRODUCT PROTECTION. The oxidation of fats generates free radicals that result in off-flavors and odors. A free radical is a highly reactive molecular species that can propagate oxidation reactions through the generation of more free radicals. The reaction is only stopped when two radicals are neutralized by an antioxidant (small molecules that can receive or donate an electron to stabilize a free radical forming a stable by-product and preventing further damage).
Chelating agents such as ethylenediaminetetracetic acid (EDTA) or citric, tartaric, ascorbic and phosphoric acids can also be used to remove the metal ions that help initiate the reaction. Acids and acid salts provide a reducing environment that will help regenerate the antioxidants throughout the shelf life of the baked product. Reducing agents already present in the formulation can also interact in this complex system. However, formulators need to achieve a balance so that all ingredients perform their own functionality without affecting one another.
The synthetic molecules that are commonly used as antioxidants for fats and oils include butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tertiary butylhydroquinone (TBHQ). These molecules resist baking and frying temperatures. However, once the antioxidant has reacted with the free radical, it is no longer capable of further protection. Thus, all the molecules would be used up during the chain reaction, and eventually the oxidation of fatty acids will continue. These molecules can help delay the process but cannot prevent it indefinitely. Another synthetic molecule, propyl gallate, is also a good antioxidant. Its molecular structure helps stabilize lard but is not as effective with vegetable oils.
Naturally derived antioxidants are also available to the baker. Tocopherols (vitamin E) are naturally present in fats and oils but are more prevalent in vegetable oils. These molecules are not stable during heat processing so they are unable to protect finished fried or baked foods.
Plant extracts have caught the eye of formulators who want to develop products with cleaner labels. Spice extracts such as rosemary and cinnamon as well as other plant extracts such as gum guaiac have a variety of phenolic constituents that also act as antioxidants. Much research is available in this arena, and one must think that extracts that have a variety of phenolic groups will do the trick. So, in this case, the choice will depend on the availability, activity, stability and the desired final product profile. The addition of antioxidants is in the range of 0.005 to 0.02%, and different molecules are usually combined to obtain the most benefit of the synergistic interactions. Another option is to use packaging materials that have incorporated an antioxidant molecule.
Protection of fats is also extremely important to protect the "healthy" status of different products. Polyunsaturated fats are, by far, the most susceptible to oxidation because of the presence of double bonds, which are more reactive. When products are formulated with ingredients that contain high levels of unsaturated fatty acids such as the omega-3, -6 and -9 fatty acids, fat protection is particularly important because these ingredients cannot perform their health protection effects if they are destroyed by degradation. In addition, the oxidation of these compounds results in unacceptable fishy tastes and smells. Some good choices for these products include tocopherols (vitamin E), ascorbic acid (vitamin C), lactoferrin, gallic acid, EDTA and natural plant and spice extracts.
CONSUMER PROTECTION. In biological systems, free radicals are produced continuously as part of regular metabolism. When this process exceeds the body’s natural ability to stop this chain reaction and protect itself, oxidation takes over and damages cells and tissues. Different studies suggest that the inclusion of antioxidant compounds in the daily diet can help prevent diverse chronic diseases and, in general, slow the aging process.
A variety of fruits, vegetables, whole grains, legumes and herbs are rich sources of beneficial molecules that include more than 4,000 known compounds. These foods are usually evaluated on the basis of the oxygen radical absorbance capacity (ORAC) or the cellular antioxidant activity (CAA). In 2004, the US Department of Agriculture (USDA) published an updated list of ORAC values for common foods. This new list now includes a total ORAC value for both lipid-soluble and water-soluble phytochemicals. It is important to consider that some ORAC evaluations are based on dry weight, while others may be based on wet weight or serving size so values may not be directly comparable.
Which fruit source is the best? It depends on who you ask. Wild blueberries have placed the highest berry in total antioxidant capacity rankings. According to the Wild Blueberry Association, Bar Harbor, ME, wild blueberries perform beautifully, maintaining their flavor, texture, shape and most importantly color (the source of antioxidant power) throughout the manufacturing process. According to the Cranberry Institute, East Wareham, MA, cranberries also rank very high in antioxidant power, but most importantly, the antioxidant content of cranberries is retained during freezing or processing into sauces, dried fruit or juice. Plums are not lagging behind. The California Dried Plum Board, Sacramento, CA, stated that plums are a good option because they contain compounds associated with lowered incidence of heart disease by protecting low-density lipoprotein (LDL or "bad") cholesterol from oxidation.
Tree nuts and peanuts are another source of antioxidants. According to the NUCIS (Health and Tree Nuts) Foundation, Reus, Spain, nuts are one of the richest foods in antioxidants such as vitamin E, beta-carotenes, ellagic acid, flavonoids and tocotrienols. The tree nuts richest in antioxidants are walnuts, followed by pecans, hazelnuts, almonds, Brazil nuts, macadamia nuts, pine kernels,
pistachios and cashews.
One drawback to using natural sources of antioxidants is that concentrations of active compounds may vary from product to product. Delivery systems may also present a problem as well as fresh product availability and handling. In addition, some antioxidant compounds have characteristic bitter flavors that would not yield an adequate sensory profile to many products. Therefore, other technological solutions may be needed to achieve the desired level of addition.
Some options include the use of liquid products such as juice, concentrates and purees. Drum-dried powders can also be used for dusting baked products and bars to add a final health-promoting touch. Drying and encapsulation technologies can be used to make custom pre-mixes that contain the exact nutrient blend designed for the required application. These pre-mixes obviously provide exact amounts of standardized compounds that have been stabilized and formulated to withstand different processes to yield a food product with unique nutritional properties.
Each ingredient needs its own regulatory evaluation, and any health claim needs to abide by the Food and Drug Administration’s rules. The addition of antioxidants to protect products from rancidity is still extremely important.
Whether antioxidants are introduced naturally through nutritionally dense ingredients or as extracts using sophisticated delivery systems, bakers can use them to make every calorie count.
This story originally appeared in the October issue of Baking & Snack.