Public liability insurance holders have been told that machines should be fully isolated before any maintenance takes place on them.
The warning comes after Tangerine Confectionary was found guilty of breaches under Section 2 of the Health and Safety at Work Act 1974 and of breaching Regulation 3(1) of the Management of Health and Safety at Work Regulations 1999.
It was fined a total of £300,000 and ordered to pay costs of £72,901.65.
Bournemouth Crown Court heard how employee Martin Pejril was killed at its Poole factory when he attempted to clear a blockage in one of the machines.
He climbed inside the unit, but as it restarted he became trapped. Mr Pejril was pronounced dead at the scene.
Simon Jones, Health and Safety Executive inspector, said: "This tragic case highlights the need to ensure that machines are safely isolated before any maintenance takes place so it cannot unexpectedly start up. Simply pressing a stop button does not adequately isolate a machine."
Earlier this month, European Metal Recycling Limited of Merseyside was fined £8,000 after a worker's hand was crushed when he attempted to clear a blockage on a magnet conveyor.