Billionaire investor Warren Buffet is dipping into the ketchup business as part of US$23.3-billion deal to buy the Heinz ketchup company.

H.J. Heinz Company says it's the largest deal ever in the food industry.

Heinz, based in Pittsburgh, also makes Classico spaghetti sauces, Ore-Ida potatoes and Smart Ones frozen meals.

"It's our kind of company," Buffett said in an interview on CNBC, noting its signature ketchup has been around for more than a century. "I've sampled it many times."

The company was founded by Henry John Heinz and his neighbour L. Clarence Noble in 1869. The pair's first product was grated horseradish, bottled in a clear glass to showcase its purity. The first ketchup was introduced in 1876; the company says it was the country's first commercial grade ketchup.

Last year, Heinz says it had sales of US$11.6 billion, with ketchup and sauces accounting for just under half of that.

Berkshire Hathaway and 3G Capital, the investment firm which bought Burger King in 2010, say Heinz will remain headquartered in Pittsburgh.

Heinz CEO William Johnson said in a statement that the company "will have an opportunity to drive further growth" as a private enterprise.

At a press conference following the announcement, Johnson said the deal got under way eight weeks ago when managing partners from 3G Capital visited him for lunch.

The men were familiar with each other because Heinz is a supplier for Burger King.

"We did not solicit this," Johnson noted. "They came to me."

Buffett said on CNBC that 3G's billionaire co-founder Jorge Lemann approached him about the Heinz deal on a plane they were on in early December.

Heinz shareholders will receive US$72.50 in cash for each share of common stock they own.

The transaction value includes the assumption of Heinz's debt. Based on Heinz's number of shares outstanding, the deal is worth US$23.3 billion, excluding debt.

The per-share price for the deal represents a 20 per cent premium to Heinz's closing price of US$60.48 on Wednesday.

Buffett said on CNBC that Berkshire is putting US$12 billion to US$13 billion into the deal.