The extract was found to be just as efficient as the legal limit of the synthetic antioxidant butylhydroxytoluene (BHT) at a concentration of between 800 and 850 ppm, report the researchers from the University of Sargodha.
"Therefore, on behalf of this study, pomegranate peel can be recommended as a potent source of antioxidants for the stabilization of food systems, especially unsaturated vegetable oils," wrote lead author Shahid Iqbal in the journal Food Research International .
Interest is growing in plant-derived food additives as replacements to synthetic antioxidants like butylhydroxyanisole (BHA) and BHT to slow down the oxidative deterioration of food.
Indeed, according to a 2003 report by Frost and Sullivan, the synthetic antioxidant market is in decline, while natural antioxidants, such as herb extracts (particularly rosemary), tocopherols (vitamin E) and ascorbates (vitamin C) are growing, pushed by easier consumer acceptance and legal requirements for market access.
This natural antioxidant range could potentially include pomegranate peel, "underestimated as an agricultural waste," according to Iqbal and co-workers, whose promising new results showed the potential of peel extracts on the thermal and storage stability of sunflower oil.
The researchers used methanol to extract antioxidants from the peels, and report a 29.2 per cent yield with an antioxidant activity of 92.7 per cent.
The extracts were subsequently added to sunflower oil at 250, 500 and 1000 ppm, and compared to sunflower oil with BHT at its legal limit of 200 ppm.
Iqbal and co-workers report that, with respect to various parameters, including weight gain, antioxidant activity index, peroxide value, and thiobarbituric acid reactive substances (TBARS), the best performance was achieved by pomegranate peel at a concentration of 1000 ppm.
This was followed by BHT at 200 ppm, and pomegranate peel at 500 and 250 ppm, respectively.
"Pomegranate peel extract at concentration of 800-850 ppm has stabilisation efficiency comparable to conventional synthetic antioxidants, i.e. BHT at its legal limit," wrote the researchers.
"It improves resistance of sunflower oil against thermal deteriorative changes.
Besides this, polyunsaturated fatty acid content is saved appreciably by creating resistance in oil against oxidative rancidity," they concluded.
In addition to the 'natural' tag that comes along with the extract, the recent surge in interest in pomegranate and its extracts as health ingredient could offer an extra bonus for the ingredient.
Pomegranate, a rich source of antioxidants, has been linked to improved heart health, but a growing body of science indicates the fruit protect against prostate cancer and slowing cartilage loss in arthritis.
It is these antioxidants, and particularly ellagitannin compounds like punicalagins and punicalins, which accounts for about half of the fruit's antioxidant ability, that are reportedly behind the proposed health benefits.
Source: Food Research International (Elsevier) Published on-line ahead of print, doi:10.1016/j.foodres.2007.11.005
"Efficiency of pomegranate peel extracts in stabilization of sunflower oil under accelerated conditions" Authors: Shahid Iqbal, S. Haleem, M. Akhtar, M. Zia-ul-Haq, J. Akbar