Science - April 22, 2004

Sorghum can be improved by listening to the sound it makes

African PhD researchers are using sound and lasers to determine the amounts of polyphenols in the staple crop sorghum. The aim is to come up with methods of reducing the amount of polyphenols in local foods.

In the West we are used to reading about the nutritional benefits of polyphenols, plant chemicals that protect the body against aggressive molecules. Nutritionists in Africa have a different view however. “Polyphenols hinder the uptake of zinc and iron,” explains Dr Maja Slingerland of the Crop and Weed Ecology group. Five sandwich PhD research assistants from African research institutes are being supervised by Wageningen scientists in their search for techniques to reduce the amount of polyphenols in staple crops. Slingerland continues: “We have taken the entire chain in this project. We want to breed sorghum varieties with fewer polyphenols and more iron and zinc, and we are also looking into whether it is possible to reduce polyphenol content during sorghum processing.”

The researchers needed a method to determine polyphenol content quickly, and the Laboratory of Biophysics, where Dr Dane Bicanic works, came up with a solution. Bicanic has been working there together with Hungarian colleagues since 1990 on a special form of spectrography. “We bombard flour with pulsating laser beams,” explains Bicanic. “The wavelength of the light determines which molecules absorb the laser light. The molecules affected release energy in the form of heat, and this makes the flour expand and contract.” A sensitive microphone records the sound of the flour as it changes. The louder the sound the more polyphenols there are in the flour. Slingerland adds, though: “This technique works well for red sorghum, but we are still having a few problems with white sorghum.” The Inref project continues until 2006.

Willem Koert