Impact of wash cycle time, temperature and detergent formulation on the hygiene effectiveness of domestic laundering

Author: 

M. Honisch, R. Stamminger and D.P. Bockmuhl
Journal of Applied Microbiology 117, 1787--1797

Abstract: 

Aims: Investigation of the effect of temperature and duration of the laundering process with and without activated oxygen bleach (AOB)-containing detergent on the hygienic effectiveness of laundering.

Methods and Results: Cotton test swatches were contaminated with Staphylococcus aureus, Enterococcus hirae, Pseudomonas aeruginosa, Candida albicans and Trichophyton mentagrophytes and were washed in a household washing machine using temperatures between 20 and 60°C and different wash cycle times. The logarithmic microbial reduction factor and cross-contamination (i.e. transfer from contaminated to sterile swatches) were used to indicate the hygienic effectiveness of the washing process. For all tested micro-organisms, the temperature needed for decontamination depended on washing time and detergent type. Hygiene effectiveness of laundering was enhanced by inclusion of AOB even at lowest temperatures, except for C. albicans, which was virtually unaffected by AOB. The use of AOBcontaining detergents as well as high washing temperatures reduced crosscontamination to sterile swatches included in the load.

Conclusions: Depending on the type of organism, longer wash cycle times or the use of AOB-containing detergents can be used to enhance the hygiene effectiveness of laundering. Significance and Impact of the Study: The study demonstrates that it is possible to compensate for the loss of hygiene effectiveness of laundering at lower temperatures using detergents with activated oxygen bleach or by extending the wash cycle time.