The mass salmonella outbreak at a Canberra restaurant that poisoned more than 160 people had the quickest incubation period one expert had ever seen, a court has heard.
And the speed at which the Copa Brazilian's customers got sick could be because of the amount of bacteria ingested, the expert said.
In May 2013, within a week of opening, the 161 customers were served a potato salad with a raw egg aioli in a $45 all-you-can eat deal.
An ACT Health investigation traced the raw eggs to a Victorian supplier, while the Dickson restaurant eventually closed in 2014.
Copa's owners, Zeffirelli Pizza Restaurant Pty Ltd, still faced criminal charges over selling unsafe food. They have pleaded not guilty.
Their defence was that they believed the food was safe to eat.
Defence lawyer Tim Sharman told the court the owners held a positive and reasonable belief the eggs were safe. He said the eggs came from a primary industry and chain of suppliers that was regulated, and the owner's were entitled to rely on that regulation.
He said the possibility of a "bad egg" was beyond the owners' control.
The court heard evidence how a crack in the shell invisible to the eye would allow salmonella to develop inside, but not be seen or smelled.
Further, at the time, the ACT had no guidelines or rules governing how to handle raw egg products, unlike other jurisdictions, Mr Sharman said.
The court was told staff were "disturbed" to hear of the outbreak.
But this was a business, and food poisoning was a risk restaurateurs should be aware of, prosecutor Michael Reardon told the court.
And there was a safer alternative in pasteurised egg products, he said, giving the owners ability to control for the risk of salmonella.
Cameron Moffat, an epidemiologist who at the time was with the ACT Health Service, said he'd never witnessed an outbreak situation that had happened on a Saturday, and he heard about on Monday.
He said the median incubation period for the outbreak was about 17 hours, while usually for salmonella it was between 24 to 72 hours.
While the age and health of a person, along with the environment, might affect the incubation period, he suggested it was "more to do with, perhaps the amount of bacteria that was ingested".
He said outbreaks could occur anywhere, and knew high-end restaurants in Canberra that had experienced a similar issue.
The use of products such as raw egg mayonnaise in restaurants was "in vogue", and causing some problems, Mr Moffatt told the court.
Radomir Krsteski, manager of the microbiology unit at ACT Health, also gave evidence at the ACT Magistrates Court on Thursday.
He said pasteurisation – a process of heating the egg products – was the safest way to ensure an egg would be free of salmonella.
He also explained how a "bad egg" with a hairline crack and kept in conditions favourable to the bacteria, could become contaminated with salmonella without someone's knowledge.
Magistrate Glenn Theakston will give his judgment at a later date.