Staff who serve food at an Auckland private girls school are undergoing training after serving sushi to students a day after its use-by date.

A group of about 50 boarders at St Cuthbert's College were served the packaged sushi, with an expiry date of Friday, for lunch on Saturday.

The error was discovered before any of the students ate the expired food, but a parent of one girl expressed concerns the students could have fallen ill right before their exams if they had eaten it.

College Principal Lynda Reid said the incident had been discussed with catering company Alliance.


When the error was spotted a different lunch was served.

"This incident is extremely concerning for the college as we expect Alliance to ensure that food safety standards are upheld to the highest level."

An Alliance statement confirmed students were "inadvertently served pre-packaged sushi after its "best before" date on Saturday".

It said the "one-off oversight" was quickly detected.

"The catering team at St Cuthbert's has been undertaking a training update on food safety [since the incident] and ongoing monitoring is in place.

"Alliance serves millions of meals each year across New Zealand and Australia and food safety is its highest priority," the company said.

Head of Nutrition and Dietetics at the University of Auckland Dr Clare Wall said food expiry labels were there for a reason. "For something like sushi, particularly if there are raw ingredients used, such as fish, I would recommend that it is not consumed past its expiry date."

She said consumers could be at risk of salmonella, campylobacter and listeria.