Sunday, April 21, 2002		Article

The hidden power of potatoes
Shirish Joshi

AFTER sugarcane and sugar beet, agriculture scientists are now turning to the humble potato for making sugar. The natural sweetener in your soft drink or chocolate bar or diabetic food could soon come from an unlikely source: potatoes. Researchers at the University of Picardie Jules Verne in Amiens, France, led by Rajbir Sangwan have genetically modified potatoes to multiply their fructose production about 40 times.

The team inserted three bacterial genes into the potato’s DNA, each gene coding for a different enzyme involved in converting starch to fructose.

Fructose is a sugar produced by nearly all fruits and by many vegetables. Fructose, also known as levulose and fruit sugar, is nearly twice as sweet as sugar made from sugarcane. Fructose is used to sweeten such food products as diet foods, gelatin desserts, jellies, soft drinks, and syrups, and is the chief sweetener in honey.

Foods that contain fructose taste as sweet as similar foods made with sugar, but they may have fewer calories. Fructose gives ice-cream and candies a smooth texture. It also absorbs moisture readily and so helps keep baked goods from becoming stale.

Fructose is produced commercially as a liquid, powder, or tablet. Most fructose is made today by adding vast quantities of enzymes to maize (corn or makka). But the genetically modified (GM) potatoes turn starch into fructose inside the vegetable. This makes for a much more efficient and economical process.

A number of food-processing companies in Europe have expressed interest in using the new technology.

The GM potato produces 40 times as much fructose as compared to an unmodified potato. It releases fructose when it is cooked. Three genes encoding enzymes capable of converting the starch stored in potatoes into fructose have been added to the plant. When the potato is heated and mashed, fructose is released, turning the humble spud into a miniature chemical factory.

The GM potato could revolutionise the food industry, enabling fructose to be produced more cheaply, from potatoes. Current methods for producing the huge quantities of fructose needed each year rely on large-scale industrial processes using starch from maize. The starch is converted into fructose in a chemical plant using bacterial enzymes that can function at high temperatures. The enzyme alpha amylase catalyses the breakdown of starch into glucose. Glucose is then changed to fructose by a second enzyme, glucose isomerase.

When the GM potato is heated for 45 minutes at 65°C, the added enzymes are activated, converting starch to fructose. It would take about three to five years before the potatoes are ready for the food industry. However, the researchers warn that anti-GM feeling in Europe and elsewhere including India may delay the applications of the new technology.