Microbiological Assessment of Utensils Cleaned by Domestic Dishwashers

[labboy]

I came across this field study that people might find of interest regarding the sanitizing ability of domestic dishwashers.

It seems like it was well controlled. However, I wonder how well the operators loaded the dishwashers? They mentioned "overloading" being more associated with failure. For me, there is a difference between overloading where not all items are able to be reached by spray and carefully loading to ensure proper washing. (In addition to ensuring the spray arms can move, adding sufficient detergent for the full load, etc.)

Bob

http://www.foodprotection.org/files/food-protection-trends/May-Jun-15-sahai.pdf

 

[fisherpaykel]

Wonder if chlorine based were only liquid/gels

Interesting read, read the whole report, shows that modern enzyme detergents tend to be more effective for reduced/allowable bacterial counts. I am not that surprised that commercial DW's tested had a similar 80% pass rate as domestic DW's 83% given that commercial machines have such short cycle times since asthe study points out remaining food deposits can protect bacteria on the dishes. I am sure I am not the only one finding soiled cutlery on a restaurant table more frequently than at home. I don't agree with their advice to have all cutlery handles down to avoid nesting and be in contact with the water spray. And they did not study that, just seems an opinion thrown in without evidence. Where does the most forceful spray come from? Down below a standard cutlery rack. For safety as well knife and fork points need to be down. If you have slots to hold spoons handle down ok for them. A vintage DW ad in recent Picture Of The Day showed all points down, just don't understand modern ads showing fork and spoon up. Who knows how clean the hands are unloading the cutlery. Study also shows benefit of a temp hold to achieve correct final rinse temperature. Would be interesting to know which 2 DW using Sanitize cycle failed. Maybe heating element burned out? Thanks Bob for posting this and wow how did you come across this study?

 

[rolls_rapide]

Mechanical Dishwashing

I came across this - a report from 1999, with an update from 2005:

"Methods for ascertaining the cleaning performance of dishwasher detergents"

It mentions when the the biological compact detergents put in an appearance: 1990/91.

https://www.ikw.org/fileadmin/ikw/downloads/Haushaltspflege/HP_DishwasherA_B_e.pdf

 

[rolls_rapide]

Food Protection Trends/Sahai paper

"Although chlorine is a well-established sanitizer,
we would not expect its presence in a detergent to improve
the chances of a dishwasher meeting the prescribed limit.
To be an effective sanitizer, chlorine must be added, in the
right concentration, during the rinse cycle, after all food
residues have been removed from the utensils during the
wash (cleaning) cycle (11)."

Hmm, I'm not sure the authors are aware of the ability of chlorine to remove staining from crockery during the wash.

Another factor - how old were the detergents used? Were they fresh, of recent manufacture? Were they months old? Were they stored in a cool dry place, or were they plonked beside a steamy dishwasher with the bag/lid open to the atmosphere? Were liquids detergents mixed in the bottle before being dispensed by the users. Too many variables.

 

[launderess]

It has been long known when chlorine bleach is used as as sanitizer/disinfectant it comes *after* surfaces or laundry has already been cleaned. Or maybe it's just me from my nursing school days.....

Key thing for sanitizing or disinfecting with chlorine bleach is knowing parts per million

https://www.doh.wa.gov/Portals/1/Documents/8340/970-216-Disinfect-en-L.pdf

https://www.thecloroxcompany.com/wp-content/uploads/5813_100_service-bulletins_20160708.pdf

https://www.cms.gov/medicare/provid...fo/downloads/survey-and-cert-letter-13-09.pdf

For this reason commercial/industrial laundries add chlorine bleach to first rinse after wash cycle or cycles. By that time much of the soil and germs that would affect sanitizing power of chlorine bleach have been removed. What remains are a much lower count that properly dosed chlorine bleach can handle.

Same for automatic dish washing. Commercial machines largely act as sanitizers as much of food or whatever should have been washed/rinsed off before items are loaded into or sent through machines. Cycles are just too short for heavy duty removal of soils on their own. Nearly all local health codes specify that when dishes are washed for public use machines in question must either have thermal or chemical means of sanitation.