July 30/News of Science -- According to a study from Erlangen, Germany, "The cytotoxic activity of Maillard reaction products and coffee was studied using the 3-(4,5-dimethylthiazol-2-yl)-2,5 -diphenyl-tetrazolium bromide (MTT) assay and the neutral red uptake (NRU) assay. Equimolar mixtures of sugars and lysine were heated at 120 degrees C and used to stimulate bovine aorta endothelial cells for 24 It."

"The cytotoxic activity increased with increase in educt concentration and heating time. Mixtures containing ribose were most active, followed by lactose and glucose. Hydrogen peroxide, which was present in the Maillard mixtures in concentrations between 7 and 87mc M, was identified as one of their major cytotoxic components. H2O2-concentrations increased further up to 130mc M under cell culture conditions. Filter coffee, espresso, and green coffee extract reduced cell viability significantly to 10, 19 and 83% of PBS-treated control. The effect was largely attenuated by the addition of catalase. Nil, 33, and 41mc M H2O2 was measured in green coffee extract, filter coffee and espresso, respectively, increasing to 13, 369, and 333mc M during cell culture conditions. No additional H2O2 formation was detected when coffee was incubated for up to five hours without further treatment," wrote J. Hegele and colleagues, University of Erlangen.

The researchers concluded, "Hydrogen peroxide is a major product in Maillard mixtures and coffee-inducing cell death in vitro."

Hegele and colleagues published the results of their research in Molecular Nutrition & Food Research ("Identification of Hydrogen Peroxide as a Major Cytotoxic Component in Maillard Reaction Mixtures and Coffee." Molecular Nutrition & Food Research, 2009;53(6):760-769).

For additional information, contact M. Pischetsrieder, University of Erlangen Nurnberg, Dept. of Chemical & Pham, Schuhstr 19, D-91052 Erlangen, Germany.

From the August 3, 2009, Prepared Foods E-dition