Antioxidant Systems: Turning to Nature for Solutions

Countering complex oxidation reactions with consumer-friendly solutions.

By Claudia Dziuk O’Donnell, Contributing Editor

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Years ago, as the clean label movement began in earnest, a high-profile, heart-healthy potato chip with a claim of “natural” was launched. Impressed by media accolades, I sampled some chips. Although the product was still within its “best by” date, I noticed a rancid taste.

The product’s development, driven by enthusiasm and consumer demand, was one of likely many that avoided added antioxidants without taking shelf life challenges into account.

Since then, clean labels have been enabled, in part, by advances in food technology. Food processors are working toward improved label-friendly solutions to oxidation, and ingredient vendors strive to provide sophisticated antioxidant ingredients with consumer-friendly names.

Components taking part in antioxidant systems can be categorized as primary antioxidants, secondary antioxidants, chelators, quenchers, oxygen scavengers and antioxidant regenerators¹. These components interfere with various stages of oxidation reactions.

Some ingredients have abilities in more than one category, and ingredient combinations can act synergistically. For example, chelators that bind pro-oxidation metals such as iron and copper, whether synthetic or natural (e.g., EDTA, phytic, phosphoric and citric acids) are often combined with primary antioxidants.

The physical properties of a food matrix as well as where antioxidant molecules are located within that matrix have a great impact on oxidation. Foods and beverages differ in the amount and type of fat (e.g., degree of saturation); in their processing, such as exposure to high temperatures and air; in their pH; water activity (aw); and exposure to pro-oxidants such as metals and light, to name just a few factors.

Natural chemicals and overlooked antioxidants

Primary antioxidants function as free radical scavengers and reducing agents. These reducing agents "donate" or lose an electron to another chemical species, such as an unsaturated lipid in redox chemical reactions.

Synthetic sources of primary antioxidants include TBHQ, BHT, PG and BHA. Other primary antioxidants include tocopherols and ascorbic acid, which can be obtained from both natural and synthetic sources. Mixed tocopherols, rosemary, sage and green tea are examples of antioxidants from natural sources.

At a Clean Label Conference presentation, Fereidoon Shahidi, university research professor at Memorial University of Newfoundland, listed categories of antioxidants found in nature. They included phenolic acids, phenylpropanoids, tocols (tocopherols and tocotrienols), flavonoids, bisoflavones, coumarins, tannins (condensed and hydrolysable) and others such as carotenoids, phospholipids, amino acids and protein hydrolysates, vitamin C, and so on. Under some circumstances, certain antioxidants can also be pro-oxidants.

Well over 5,000 polyphenolic compounds have been identified in plants. They perform functions that include attracting pollinators, participating in a plant’s wound-healing and protecting against predators as well as their own oxidative stress, Shahidi noted.

While consumers may shy away from “chemical-sounding” names, commercially popular and consumer-friendly rosemary extracts contain key antioxidant chemicals including carnosic acid, carnosol and rosmarinic acid. These and other antioxidants have varying polarity, which enables them to be beneficial in a range of applications due in part to their affinity for lipid or aqueous phases.

Depending on a final product's required sensory profile and composition, formulated products can take advantage of oxidation-fighting components. Examples include those contributed by spices and herbs (e.g., flavonoids, phenolic acids, coumarins); oils and oilseeds (e.g., tocopherols, lignans, phospholipids, phenolic acids); cereals and grains (e.g., flavonoids, phenolic acid esters, lignans, sterols); and fruits and vegetables (e.g., ascorbic acids, carotenoids, hydrolylated carboxylic acids) among others.

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