Technical Talk: July 2010

Antioxidant is a buzzword in today’s food marketing strategies.
Consumers are increasingly aware of the connection between antioxidants
in food and prevention of chronic diseases, such as cancer and
diabetes. Recent market research data from the United States indicates
that a large number of consumers will select products that contain the
phrase “rich in antioxidants” on the package, and many will consider
buying products labelled “antioxidants added.”

Antioxidant is a buzzword in today’s food marketing strategies. Consumers are increasingly aware of the connection between antioxidants in food and prevention of chronic diseases, such as cancer and diabetes. Recent market research data from the United States indicates that a large number of consumers will select products that contain the phrase “rich in antioxidants” on the package, and many will consider buying products labelled “antioxidants added.”

But what exactly are antioxidants, and how do they work? First, let us define oxidation. Simply put, oxidation is the effect oxygen has on fats and oils during their shelf life.

In the food industry, fats and oils are used as functional ingredients. These are mainly triglycerides of different composition, and their configuration determines their oxidative stability. For example, saturated fats or partially hydrogenated fats are very stable and resistant to oxidation. However, mono and polyunsaturated fats and oils are more prone to the oxidation process.

The oxidation process, before it is even detectable, begins with the formation of radicals, which initiate and accelerate the process that will eventually result in rancidity. This process is also referred to as auto-oxidation because is not mediated by the presence of enzymes, as we will discuss later on.
Oxidation also affects plant and animal tissues. For example, human and animal cell membranes contain phospholipids, which play an important role in the functionality of the cells. These radicals will result in the oxidation of the phospholipids and damage to the cells. This process may eventually result in the onset of chronic diseases.

Enzymes can also mediate the oxidation process. For example, after being cut or peeled, apples and potatoes will turn brown due to an enzyme naturally present in these foods. This type of oxidation is caused by the activity of certain enzymes such as lipases and peroxidases. This process affects fruits and vegetables as well as grains and other seeds. As soon as the grain kernel or seed is broken open, the oxidation process begins. By exposure to heat, it is possible to deactivate these enzymes and extend the shelf life of cereal ingredients such as wheat germ and bran. However, the auto-oxidation process will continue and the addition of antioxidants will be required to extend the shelf life of these products or ingredients.

Antioxidants are substances that will slow or eliminate oxidation of fats and lipids. Their use will prevent the rancidity of foods or damage to cell membranes in our bodies. Several antioxidants are available for use in food processing. These include synthetic antioxidants such as butylated hydroxy anisole (BHA), propyl gallate (PG) and tertiary butyl hydroxy quinone (TBHQ), and natural antioxidants such as rosemary extract, tocopherols (vitamin E), cloves and cinnamon.

The recent emphasis on antioxidants, however, focuses on the relationship of these substances and the prevention of chronic diseases. Indeed, much research has been carried out in recent years connecting this relationship. The focus has been in the area of natural antioxidants present in fruits, vegetables, seeds, grains and other plant parts. Many fruits and vegetables have been investigated for their antioxidant ability, and their capacity has been determined. In addition, the actual substances responsible for the antioxidant activity within these vegetables and fruits have been identified.

Natural antioxidant activity can be measured by different methods. One of the most popular methods is the determination of oxygen radical absorbance capacity (ORAC) value.

The highest quantities of these antioxidants are often present in outer layers such as skin and bran, which, based on traditional processing, are discarded as byproducts. Recently, however, the health benefits of these byproducts are beginning to be recognized. Investigations at the Guelph Food Technology Centre resulted in a new process for the production of grape-skin flour, which is high in the antioxidant resveratrol.

The food processing industry is pressed to reduce byproducts or find ways to add value to them. There are various reasons for this, including economics, sustainability and environmental issues. Indeed, researchers in many parts of the world are investigating byproducts such as fruit peelings, pulp, seeds, skins and many others for their antioxidant capacity and the production of ingredients from these byproducts. Specifically, skins of tomatoes, apples, peaches, pears, grapes, plums and other fruits were found to often contain more antioxidants than the whole fruit itself.

Commercial production processes for stable ingredients from these antioxidant-rich byproducts must be carefully considered. Normally, ingredients for the food processing industry are in the form of powders. The production of powders from these products requires dehydration – which is usually achieved via exposure to heat – but this reduces, and sometimes completely eliminates, the antioxidant activity.

New, “gentler” processing technologies have emerged to accommodate the need for powders. These technologies are capable of dehydrating fruits, vegetables and their processing byproducts to shelf-stable powders while at the same time preserving their antioxidant activity. In addition to preserving the antioxidant activity of ingredients, this exercise will be meaningless if the antioxidants cannot reach the consumer. It is therefore imperative that the processing of food products is not so severe as to destroy the antioxidants. However, it is also important that the food processing adequately safeguards the consumer from the danger of food pathogens, and provides the quality parameters the food product requires.

Many manufacturers supply ingredients that claim to be of high antioxidant capacity and provide certain health benefits. When you purchase such ingredients, make sure the claims are substantiated and your production process does not negatively affect their antioxidant activity before using them in your products.

Dr. John Michaelides is Guelph Food Technology Institute’s director of research and technology. For more information, or fee-for-service help with product or process development needs, please contact GFTC at 519-821-1246 or gftc@gftc.ca.