Accumulated scum on an industrial-sized food mixer has been blamed for a major salmonella outbreak at the Burnside War Memorial Hospital in Adelaide.

SA Health says its investigations revealed that a stab mixer was the source of the contamination.

SA Health's director of food safety and nutrition Fay Jenkins said she was “a bit shocked that it was so dirty”, but explained that hospital staff believed (incorrectly) that the appliance was being cleaned properly.

Investigators heard that the machine actually required a technician to disassemble it to be cleaned properly, so food waste was allowed to build up in its inner-workings.

“Due to the way it was constructed, the mixer was unable to be dismantled, which meant thorough cleaning and sanitising could not occur and harmful bacteria were able to survive within the appliance,” Ms Jenkins said.

“The stab mixer has since been removed from the Burnside War Memorial Hospital kitchen and further actions have been taken to prevent potential cross contamination.”

There are now 16 patients with gastroenteritis linked to the private hospital.

Health Minister Jack Snelling says the hospital will now only use mixers that can be easily dismantled for cleaning.

“In the particular case of this mixer, a technician actually had to be brought in to pull the mixer apart to enable it to be cleaned properly,” he said.

“These mixers that otherwise appear perfectly clean, lurking inside them can be some very, very nasty germs.

“This is a very important time to give a warning out to all South Australians, but especially those in commercial kitchens, to make sure that their mixers are able to be properly cleaned, that there isn't food residue building up in parts of the mixer that can't be accessed.”

Like public hospitals, Burnside Hospital is meant to be subject to auditing. However for private hospitals the process is not carried out by the health department, and instead falls to “a mixture of the local councils”, Ms Jenkins said.

“This sort of thing should have been picked up and they were looking at whether it was being cleaned properly and it appeared to be, but it's not until we actually took it apart and looked at it and actually took some samples that we found it wasn't being cleaned properly,” she said.

Details about the case are now being passed on to Consumer Affairs, which will decide whether it should publicly identify the brand of mixer responsible.