Chemical method offers a new approach for confirming the identity of white wines

When you buy a bottle of white wine, how do you know that the liquid inside corresponds to the Riesling, Chardonnay, or Sauvignon Blanc varietal written on the label? Variations in weather, geography, and pruning can impact a given year’s complex chemical makeup, even among wines from the same grape variety, making it difficult to develop analytical techniques for wine fingerprinting. Researchers led by Uwe H. F. Bunz of ­Heidelberg University have reported a new telltale sensing technique based on fluorescence quenching of wine alcohols, sugars, and natural colorants by two oppositely charged poly(p-phenyleneethynylene)s called PPE 1 and PPE 2 (Angew. Chem. Int. Ed. 2016, DOI: 10.1002/anie.201602385). Using an array of anionic PPE 1 and cationic PPE 2 at different pH levels, the team found that it could distinguish an assortment of white wines according to their type of grape. Although researchers have been developing wine-sensing methods based on mass spectrometry, colorimetric assays, and other techniques, “we don’t have the magic bullet yet,” comments Susan E. Ebeler, a wine chemist at the University of California, Davis. The new work is a promising first step, she adds.