US researchers have found that higher temperatures and dry weather could actually alter soy nutritional value by increasing its antioxidants content.

Agricultural Research Service (ARS) scientists led by plant physiologist Steven Britz from Beltsville Human Nutrition Research Center in Beltsville, Maryland, collaborated with William Kenworthy from the University of Maryland in College Park who engaged in research on soy's tocopherol content.

Researchers said weather and climate affect soy's tocopherol content. Tocopherols are a family of antioxidants that protect biological membranes.

For the study, the researchers analyzed the content of tocopherols in soy seeds grown at several locations in Maryland between 1999 and 2002. Weather was relatively normal between 1999 and 2001, but extreme drought and warmer temperatures occurred in 2002.

Since soy mature at different rates, the researchers examined up to 18 soy lines representing different maturity groups. There were small but significant increases in the proportion of alpha-tocopherol in soy from the same genetic line grown in warmer, full-season Eastern Shore locations compared to beans that matured under slightly cooler conditions.

Another interesting finding was that under extreme drought conditions in 2002, early maturing lines had as much as a 3.5-fold increase in relative alpha-tocopherol content, compared to the other years when rainfall was adequate.

The field studies showed how nutritional properties of crops can be seriously affected by weather and also by global environmental change, according to the scientists.