an investigation of domestic laundry in europe - habits ... - SIFO

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96An investigation into the domestic laundry habits in Europe4.5.1 RepeatabilityIf the samples are treated in a similar way in a series of independent tests, willthey yield the same results? The repeatability of the testing method is evaluatedusing two laundry samples, a dishcloth and a diaper, and a sterile samplein a 40°C cotton programme. These laundry samples are chosen because oftheir relatively high numbers of CFU in previous tests. The samples are onlytested for the Total Plate Count, Enterobacteriaceae and Bacilli.The test is repeated five times in two identical household washing machines(Miele Novotronic W362). The dishcloth and diaper were sampled accordingthe method described in 4.4. One sample of the dishcloth, one sample of thediaper and a sterile sample were washed in each was cycle with 3.3kg gammasterilised laundry at 40°C. twelve and one-half ml defibrinated sheep blood(Biotrading) was added per kg laundry to increase the soil level. The waterhardness was 9°dH and 52g Ariel Color (compact detergent without bleachingagents) was added into the dispenser. The samples were collected and the micro-organismswere enumerated after washing. The results are presented intable 4-6 The Petri dish from one of the sterile samples (run 5) was contaminated;thus, the logarithmic count is not available. The other logarithmiccounts are very much in line with each other. The maximum difference betweenthe runs is about 1 log unit.Table 4-5 Results of the repetitions of the test method at 40°C [logarithmic count of CFUin 4.7 cm2 sample]run 1 run 2 run 3 run 4 run 5Total Plate CountDiaper 4.2 3.9 4.6 3.9 4.0Dishcloth 6.4 6.0 6.1 5.7 5.6Sterile sample 4.1 4.0 4.2 4.2 3.9EnterobacteriaceaeDiaper 2.8 2.5 3.3 2.6 2.9Dishcloth 4.3 3.8 4.0 3.8 4.3Sterile sample 2.7 2.6 2.6 2.0 2.8BacillusDiaper 4.1 3.8 4.4 3.6 3.9Dishcloth 2.4 1.3 1.9 1.5 1.6Sterile sample 3.7 3.6 3.7 2.5 n/aStatistic analysis did not show any significant differences between the fiveruns (ANOVA-One Way, α = 0.05). Therefore, the method seems to be repeatable.
Hygiene effects of laundry processes in Europe 974.5.2 ValidationAs table 4-6 shows, the newly developed test method is repeatable. Anotherrelevant question is whether the test reflects common daily household practice.Therefore the results of the laboratory tests are compared to the results ofa microbiological count of a normal household wash. Several private Dutchhouseholds were asked to bring their every day dirty laundry to the laboratory.It had to be laundry that they would normally wash in a 60°C cotton programme.The 60°C programme is used in the Netherlands for washing underwear,dishcloths etc. These laundry items were also selected for the laboratorytests and were washed at 40°C. In this way the results are readily comparable.The same household washing machines were used for this test as in the previouslaboratory tests. A 95 °C cotton cycle was run in advance to reduce backgroundmicroflora. The members of the households were instructed to load thewashing machine in a way they normally would. They were asked to bringtheir own detergent and to use the dosage they would normally use. A 40°C or60°C cotton programme was used. A sterile sample was added to each process.After washing, this sample was collected and enumerated for the TotalPlate Count, Enterobacteriaceae, Bacilli and Staphylococcus aureus. The resultsof the colony counts are compared to the average test results from thelaboratory tests. These results are presented in table 4.7 and table 4.8. Thewashes from the households are labelled wash A, wash B, etc.Table 4-6 Hygienic quality of sterile samples after washing at 40°C [logarithmic count ofCFU in 4.7 cm2 sample]average wash A wash B wash C wash D wash EresultslaboratorytestsTotal Plate Count 3.9 4.5 3.5 4.1 3.3 5.4Enterobacteriaceae 3.3
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Page 119 and 120: Appendix ASurvey of domestic laundr
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Page 129 and 130: Appendix CSettings of the 15°C Was
Page 131 and 132: Appendix DSettings of the 30°C Was
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