Microbial survival and odor in laundry

The survival and distribution of microflora during laundering at 30 or 40 d egreesC in commercial U.S. and European Union (E.U.) detergents were determ ined in laboratory wash experiments. Four test strains-Staphylococcus epide rmidis, S. aureus, Escherichia coli, and Pseudomonas aeruginosa-were evalua ted on cotton textile. A significant survival and transfer between textiles were found for all four test strains washed in E.U. and U.S. color deterge nts (without bleach), whereas no survival was observed in bleach-containing detergents. Gram-negative strains generally survived in greater numbers th an Gram-positive strains. A greater survival was observed in U.S. detergent s at U.S. conditions (30 degreesC, 12 min) than in E.U. detergents at E.U. conditions (40 degreesC, 30 min). The adhesion of odorants to cotton and po lyester textiles during washing and drying was studied using six previously identified odorants in laundry [ethylbutanoate, (Z)-4-heptenal, (E)-2-none nal, 3-methylbutanoic acid, 2-methoxyphenol (guaiacol) and 4-methyloctanoic acid]. All odorants were effectively removed from cotton during wash, wher eas the odorants were more strongly associated with polyester fibers. Durin g wash, hydrophobic odorants [(Z)-4-heptenal, (E)-2-nonenal, and guaiacol] adhered more strongly to polyester than the acids. The odor formed by survi ving skin microflora attached to textiles soiled with human sebum and sweat after laundering at 30 degreesC was studied by sensory evaluation and arom a extract dilution analysis. Intensive odor was formed in both cotton and p olyester textiles during prolonged drying. Generally, the odor formation in cotton swatches and the bacterial count of the wash liquor from cotton swa tches were greater than the odor formation and bacterial count from polyest er swatches. Odorants with animal notes (branched fatty acids) dominated th e odor profile after prolonged drying. Polyester swatches possessed a more complex odor profile than cotton; in particular, aldehydes were more domina ting in polyester than in cotton. A high-impact and malodorous component, 3 -methylindole, was formed during prolonged drying in cotton. The study demo nstrates that microbial odor formation is a dominating factor determining t he odor impression of laundered cotton and polyester textiles dried under s low drying conditions. The initial soiling with aromatic components has an additional impact on the odor profile of polyester textiles after wash, due to strong adherence of odorants during the wash cycle.