The sesquiterpene rotundone gives pepper its distinctive aroma, an international group of researchers argues in a pair of papers in the Journal of Agricultural & Food Chemistry (DOI: 10.1021/jf800183k and 10.1021/jf800184t). Previously, the aroma of black pepper was attributed to complex interactions of many chemical components, including piperine and related alkaloids that produce a spicy heat sensation in the mouth. The researchers, led by Alan P. Pollnitz of the Australian Wine Research Institute, in Adelaide, found rotundone not only in white and black pepper but also in marjoram, oregano, rosemary, basil, thyme, and geranium. In addition, they identified the compound as the source of a peppery or spicy aroma in some Shiraz wines. Some aroma testers were able to sniff out the sesquiterpene at concentrations as low as 0.4 ng/L in water and in wine, making rotundone one of the most powerful aroma compounds known. Others were unable to detect the compound even at high concentrations, suggesting that flavor perceptions of wine or ground pepper in food may vary widely among consumers, the authors say.