Tillery Valley Foods, the Sodexho-owned foodservice company, has suspended 12 members of staff following broadcast of Channel 4's Dispatches programme last week (13 May).
The company said in a statement: "We are appalled by the disgraceful behaviour of a very small number of staff at TVF who repeatedly and knowingly acted with blatant disregard for the company's strict policies regarding food hygiene."
Michelle Hanson, the managing director of TVF, said that 12 members of staff were subject to disciplinary action. She said: "Their actions do not reflect the very high standards adhered to by the remainder of our 450-strong staff, who take pride in their work."
The company said it had also taken steps to shore up the hygiene standards on its production line by installing CCTV throughout the Gwent factory.
The NHS's Purchasing And Supply Agency (PASA) said that TVF had reassured it that it would restore its standards by improving its management and supervisory structure and retraining every employee in food hygiene.
PASA added that its food safety auditor, STS, revisited TVF on 23 April and asked for action on the hygiene points raised in the Dispatches documentary, which the company must address within a month.
It said: "Trusts should be reassured that we will be working with all our suppliers to ensure they all fully comply with the NHS Code of Practice."
The programme also questioned the nutritional value of food supplied by Essex-based foodservice company Anglia Crown.
Neil Kirk, chairman of Anglia Crown, said that his company's three-compartment meals, eaten with a sweet, met all the NHS's nutritional and calorie requirements.
And Scott Teasdale, hotel services manager for facilities management company Serco, which runs the facility services at the new private finance initiative hospital in Norwich, defended the company, saying that he was very happy with the safety and nutritional quality of food from Anglia Crown.
He believed that the cook-chill process was being unfairly maligned. He said: "It is surprising that people never think of Marks & Spencer ready-meals in the same light, but in hospitals they are perceived poorly."
Hanson added that there was no scientific evidence that meals freshly cooked in a bulk feeding environment were any more nutritious than meals generated using a cook-chill process.