A new test developed by U.S. Department of Agriculture (USDA) scientists is now measuring the health-promoting compounds in fruits and vegetables. This story from the USDA’s Agricultural Research Service (ARS) says the new analytical method is better for detecting and measuring concentrations of phytochemicals called “polyphenols” in plant materials.

At the ARS Eastern Regional Research Center (ERRC) in Wyndmoor, Pennsylvania, scientists first reported on the new test and used it on a variety of samples of beverages, grains and flaxseed. They used the new laboratory method to measure the amount of phenolics in various food samples by mixing them with Fast Blue BB diazonium salt. Under alkaline conditions, diazonium salt specifically couples with phenolics to form stable complexes that can be directly measured. The team then compared the new Fast Blue BB method to results using a traditional assay called Folin-Ciocalteu (FC). The results suggested that FC does not assess all phenolics present during tests and inadvertently measures other compounds besides phenolics.

While the Fast Blue BB method, as originally developed at the ERRC, was aimed at measuring phenolics only in plant tissue that does not contain chlorophyll, other ARS researchers reasoned that the test should also work with green vegetables if the test is modified.

The story is part of the ARS’ Food and Nutrition Research Briefs.