A New Zealand bakery was ordered to pay more than 11,000 New Zealand dollars, the equivalent to $7,700, for selling a pie with a dangerous filling — metal slivers.

A customer, Brendon Love, needed emergency surgery to remove a metal shaving from his stomach after eating a contaminated breakfast pie in August last year, New Zealand's Food Safety Authority told a court.

Researchers at Canterbury University found a faulty can opener caused the metal slivers.

Love spent 11 days in the hospital, suffered swelling of his intestinal tract and continues to have difficulties moving, the government-funded agency said.

The bakery, McGregor's Wanaka (2006), admitted selling food that was injurious or harmful to health under the Food Act.

Judge Kevin Phillips ordered the bakery to pay $4,100 to Love for emotional harm, and $3,600 in court expenses.

Food Safety Authority director of compliance Geoff Allen said the conviction was a lesson to food businesses that they had an "absolute responsibility" to ensure the safety of the food they sold.