Premier Foods has announced that it plans to shut down its Hovis Rank mill at Barry Docks by the end of October, as part of its plans to restructure its milling business.
The closure could result in the loss of up to 43 jobs, and ends 109 years of flour milling at the South Wales site.
Premier, which manufactures Hovis Bread and Mr Kipling cakes, said that the plans would be phased over the next few months.
It added that consultations with employees at Barry were currently ongoing.
Plaid Cymru councillor for Barry town centre Ian Johnson called the closure a "great blow for Barry", and stated that he hoped the company would reconsider its decision.
The news comes after the firm recently moved out of its Glasgow mill in early April, which affected around 15 workers.
Premier will now split its milling business into two parts, with sites in Southampton, Newbridge and Manchester being expected to focus on the production of flour for supermarkets and other manufacturers.
Investec analyst Martin Deboo told Food Manufacture that the restructuring could see the company sell its milling business altogether.
He said: "Premier could either sell the third party milling business – which is what ABF did to ADF 15 years ago, or sell the whole milling business."
He added that he believed that the debt-laden company needed to close down the mill at Barry Docks, and said that he was confident about the future of the firm.
Bob Spooner, managing director of Premier Foods’ bread division and group supply chain director, said: "We recognise the impact this proposal will have for our employees in Barry and we thank them for their contribution over the years.
"However, it’s not possible to continue on the current path given excess capacity in the marketplace."
The wider business at Premier is currently experiencing a variety of financial struggles, and recently reported debts of around £1 billion.
It is subsequently aiming to save around another £20 million this year through both the restructuring plans and measures aimed at cutting costs.