OSHA began its investigation in July last year after the accident which took place at the processing plant in New Jersey, owned by Cocoa Services Inc and managed and operated by Lyons and Sons.
The employee fell into a tank converting hard chocolate to liquid chocolate.
According to OSHA, the serious violations for both companies include a lack of railing on floor openings or working platforms above the melting tanks, employees working on melting platform exposed to nine-foot falls, employer failing to post warning signs on the melting tanks to indicate confined space and the employer failing to provide fire extinguisher training upon initial employment and annually thereafter.
Additional violations for Lyons and Sons include failing to provide enclosures or guards over energized wires on melting tank boilers and failing to provide a first aid programme.
OSHA said Lyons & Sons was assessed a penalty of $21,750 (€15,000) and Cocoa Services LP a penalty of $17,450 (€12,038).
Temporary worker Vincent Smith was tipping solid chocolate into the melting vat when he slipped from a platform into the 2.5m (8ft) deep unit. Smith apparently died instantly from a blow to his head from a paddle which was mixing the chocolate, said a spokesman for the local prosecutor's office at the time of the accident.
The spokesman, Jason Laughlin said: "There are paddles, called agitators which are moving inside this vat. He was hit by one of them before someone could hit the shut-off valve." Three other people were on the platform at the time of the accident.
Smith was in the vat for about 10 minutes before rescue crews managed to recover his body.
Investigators said the chocolate had reached a temperature of 49F (120F). The accident happened during the production of a batch of chocolate destined for Hershey's.
In July 2002, a 19-year-old worker died after falling into a vat for mixing and melting chocolate at a plant in Hatfield Township, Montgomery County, Maryland. In August 2006, a 21-year-old man survived after spending two hours trapped in a vat of chocolate at the Debelis Corporation, Wisconsin.
Meanwhile, 51 people died in food manufacturing accidents in 2007, according to the US Department of Labor’s Statistics Census of Fatal Occupational Injuries for that year.