October 30, 2013 — Antioxidants, when present in food or in the body at low levels, can delay, control or prevent oxidative processes leading to food quality deterioration or initiation and propagation of degenerative diseases. Antioxidants are generally phenolic and polyphenolic in nature and can be either synthetic or natural. When used properly, natural antioxidants maximize shelflife.
Effective at low concentrations, antioxidants are nontoxic; have good carry-through properties; and often are of reasonable cost, said Fereidoon Shahidi, University Research Professor in the Department of Biochemistry at Memorial University of Newfoundland in St.John’s, Canada. Shahidi participated in Global Food Forums’ 2014 Clean Label Conference as he gave the presentation “Natural Antioxidants: Maximizing Effectiveness for Shelflife Extension.” Primary antioxidants act as free radical scavengers and reducing agents. Synthetic antioxidants in foods include BHA, BHT, TBHQ and PG. Ascorbic acid and tocopherol can either be synthetic or naturally sourced, while mixed tocopherols, rosemary, sage and green tea are natural. Secondary antioxidants include EDTA and citric acid, which deactivate pro-oxidants.
Consumers now demand clean labels with no artificial ingredients, while longer shelflives and stability in foods are also expected. “Food processors can meet the needs of both groups by using plant-derived natural extracts,” offered Shahidi.
Over 5,000 polyphenolics have been identified in different plants. These compounds are present to protect plants against herbivores; attack by microorganisms; and from stress due to sunlight. Antioxidants also participate in wound-healing in plants, and they attract pollinators.
Important components of functional foods, antioxidants occur as phenolic acids (hydroxybenzoic acid derivatives), phenylpropanoids (cinnamic acid derivatives), tocols (tocopherols and tocotrienols), flavonoids, isoflavones, coumarins, tannins, carotenoids, phospholipids, amino acids, protein hydrolysates, ascorbic acid (vitamin C) and many more.
Lipid oxidation, causing flavor, odor and shortened shelflives in food, happens with time, light, heat or enzymes. Metals, like iron and copper, which all foods have, are initiators. With iron, Fe2+ is more soluble than Fe3+ and is more than 100 times more reactive than ferric.
“Photooxidation requires singlet oxygen, produced by interaction of light and a sensitizer like chlorophyll. This reaction is unaffected by most antioxidants but is inhibited by quenchers of singlet oxygen, such as beta-carotene,” Shahidi stated.
Natural antioxidants are available commercially. Rosemary extract, green tea extract and mixed tocopherols are commonly used in clean label products. Rosemary has
FDA GRAS status (21CFR 182.10); it contains carnosic acid and carnosol, extending shelflife in meats, poultry, seafood, edible oils, snacks, sauces and dairy products. Green tea contains catechins and can be used in the same products as rosemary. Natural tocopherols are usually a mixture from deodorizer distillate. The most abundant
and commonly used is from soybean oil processing, containing mainly gamma, delta and alpha tocopherol.
Applications for rosemary and green tea extracts include meat, poultry and seafood, which are highly susceptible to oxidation, resulting in a warmed-over flavor, discoloration and protein degeneration. Baked products are susceptible to oxidation because of long shelflife requirements. Mayonnaise, dressings, soups and sauces have a large oil-water interface and complex food matrix that increases their susceptibility to lipid oxidation.
Oxidation risk also is high in margarines, which have a biphasic food matrix. Meanwhile, shortenings are more saturated, but one needs to be aware of their trans fatty acid content and governing regulations. Nutrient content claims can also be made for antioxidants,
if they have an established RDI according to 21CFR 101.54(g) and are present in amounts qualifying for the claims. Vitamins A, C and E, riboflavin and selenium are examples.
Antioxidants without RDIs do not qualify, and many warning letters have been issued by FDA for misuse of the term, advised Shahidi. Many plant extracts provide naturally derived antioxidants that offer both clean labels and health benefits in foods, he concluded.
Fereidoon Shahidi, Ph.D., Department of Biochemistry,Memorial University of Newfoundland, St. John’s, NL,Canada A1B 3X9
The above summary on how natural antioxidants maximize shelflife is an excerpt from Global Food Forums’ “2013 Clean Label Conference Post Conference Summary.”
