Apply DNA technology to test food for adulteration.

Pasta is usually prepared from durum wheat, but less expensive wheat may be added, especially when durum is expensive or in short supply. DNA techniques are being applied to accurately measure any cheaper common wheat that is present in durum wheat pasta and to identify the characteristics of Basmati rice and other specialty rice.

Although durum and common wheat share a common ancestry, their genetic composition is different. Common wheat has one more set of genes, called D-genome, than durum. Immunoassays and other techniques are on the market that determine whether specific proteins (gliadins) produced by the D-genome are present. The amount indicates the level of adulteration.

But the levels of proteins can be affected by growing conditions and the heat process that is used to dry the pasta. A new technique developed in Europe uses a specific DNA sequence on the D-genome to determine if a product is adulterated. The method enables you to accurately determine if common wheat is present in dried or fresh pasta, unaffected by variety, growing or processing conditions.

Certain varieties of rice, such as Basmati, are highly prized for their aroma and cooking properties. Scientists have developed a DNA technique that examines simple DNA repeat sequences that occur interspersed between the gene sequences of the rice. Comparing the different lengths of these simple sequences and the number of times they occur in the genome enables you to characterize one variety of rice from another.

Researchers have developed a protocol that compares the simple sequence length polymorphisms in different varieties of long-grain rice and allows for different varieties to be distinguished from one another. It's possible to make the test quantitative. It will work with brown, milled and parboiled rice.

Further information. M.L. Woolfe, Food Labeling and Standards Division, Ministry of Agriculture, Fisheries and Food, Room 317, Ergon House c/o Nobel House, 17 Smith Square, London SW1P 3JR, England, U.K.; phone: [phone]; fax: [phone].