Identification of novel malodour compounds in laundry

We investigated malodorous compounds on clothes in daily use and identified, for the first time, middle-chain fatty acids responsible for the malodour often described as ‘wet and dirty dust-cloth-like’. Application of a preparative fraction collector and gas chromatography–mass spectrometry of the acidic volatile fraction carefully isolated from used clothes revealed the newly identified odorants responsible for unpleasant odours. In particular, the olfactory threshold of 4-methyl-3-hexenoic acid (4M3H), which has the ‘wet and dirty dust-cloth-like’ odour, was found to be the lowest among the detected fatty acids. Although 4M3H was present in trace amounts in the clothes tested (up to 5 µg/50 g cloth), an aroma extract dilution analysis revealed that it contributed the highest to the overall strength of malodour on them. In addition, quantitative analysis of the detected fatty acids in the clothes revealed a correlation between the logarithm of several fatty acid concentrations (their amount in the clothes) and the overall odour intensity. In particular, 4M3H showed a high correlation value (r = 0.72, p < 0.05). These results provide proof that these odorants can be used as indicators to assess the effectiveness of detergents and to develop a new deodorant technology. Copyright © 2011 John Wiley & Sons, Ltd.