Kazunori Hironaka who lead the research said: "We found that treating the potatoes with ultrasound or electricity for 5-30 minutes increased the amounts of antioxidants –– including phenols and chlorogenic acid –– by as much as 50 per cent."
Commonly found in fruit and vegetables, antioxidants are substances that protect cells from the damage caused by unstable molecules known as free radicals. In doing so they are thought to prevent chronic diseases, such as cardiovascular disease, various cancers, diabetes, and neurological diseases.
The ultrasound treatment consisted of immersing whole potatoes in water and subjecting them to ultra sound for between five to 10 minutes.
The electrical treatment involved immersing the potatoes in a salt solution for 10 seconds and then applying a small electrical charge for 10, 20, and 30 minutes.
Reseachers then measured both the antioxidant activity and the phenolic content. Both treatments increased signifantly the stressed potatoes’ antioxidant content. For example, t he five minute ultrasound treatment increased polyphenol levels by 1.2 times and other antioxidants by about 1.6 times. Subsequent results revealed that antioxidant levels had rocketed by up to 60 per cent.
"We knew from research done in the past that drought, bruising, and other stresses could stimulate the accumulation of beneficial phenolic compounds in fresh produce," said Hironaka who is with Obihiro University in Hokkaido, Japan. "We found that there hasn't been any research on the healthful effects of using mechanical processes to stress vegetables. So we decided in this study to evaluate effect of ultrasound and electric treatments on polyphenols and other antioxidants in potatoes."
Growing consumer interest in healthy or functional foods could mean a bright future for the low cost and straight-forward treatment techniques.
Foods normally associated with antioxidant capabities are the so-called superfruits such as cranberries and kiwi fruit together with nuts, chocolate, soy, and wine that may offer health benefits beyond traditional nutrition in term so reducing the risk of specific dieases.
Hironaka estimated the sales value of such foods as being $20bn/year in the US alone.
Potatoes are the world's fifth most widely-consumed plant food and are already regarded as a good source of antioxidants, including vitamin C and compounds called polyphenols.
Plants create antioxidants to help them combat stress in the form of attacks by pests and diseases and drought.
The research findings were reported at the 240th National Meeting of the American Chemical Society (ACS), in Boston, USA.