JAB Holdings, the owner of Caribou Coffee and Peet's Coffee & Tea, said on Wednesday it would buy U.S. bakery chain Panera Bread Co (PNRA.O) in a deal valued at about US$7.5 billion, including debt, as it expands its coffee and breakfast empire.

JAB Holdings offered US$315 in cash per Panera share, representing a 20.3 per cent premium to the stock's closing price on March 31, the last trading day before media reports of a potential deal.

Panera shares had risen about 4.6 per cent from March 31 through Tuesday's close of $274. The stock jumped nearly another 13 per cent to US$309.49 in premarket trading on Wednesday.

Luxembourg-based JAB, the investment vehicle of Germany's billionaire Reimann family, has snapped up several U.S.-based breakfast and coffee companies in recent years, including Krispy Kreme Doughnuts and K-cup coffee pod-maker Keurig Green Mountain Inc.

JAB became the world's largest pure-play coffee maker by volume in 2015, when its created Jacobs Douwe Egberts in Europe, a joint venture that combined its D.E. Master Blenders 1753 business with the coffee business of U.S.-based Mondelez International Inc (MDLZ.O).

Panera has 2,000 bakery cafes throughout the United States and its fresh offerings appeal to health-conscious consumers. The St. Louis-based company has reported better-than-expected earnings per share for the last six quarters.

The deal includes the assumption of about $340 million of net debt, JAB Holdings and Panera said in a joint statement.

Panera founder and Chief Executive Ron Shaich and entities affiliated have agreed to vote shares representing about 15.5 per cent of the company's voting power in favour of the deal.

JAB Holding also has controlling stakes in cosmetics company Coty Inc (COTY.N) and luxury goods maker Jimmy Choo (CHOO.L) among other companies.

Panera is being advised by Morgan Stanley & Co LLC and Sullivan & Cromwell LLP is providing legal counsel.