Danone SA has agreed to buy WhiteWave Foods Co for about $10 billion to add the best-selling US soy milk brand Silk and expand in organic food in its biggest acquisition in almost a decade.

Investors will receive $56.25 a share in cash, Danone said in a statement on Thursday. That's 19 percent higher than WhiteWave's closing price on Wednesday. WhiteWave began trading in 2012 after US dairy company Dean Foods Co spun off the unit, which was its most profitable business.

The acquisition would make Danone the global leader in fresh dairy and health-food brands including Horizon milk, Wallaby Organic yogurt and Earthbound Farm packaged salads as consumers increasingly shun processed foods perceived as unhealthy. WhiteWave's Silk is the biggest-selling soy milk brand in the US, benefiting from a shift to dairy alternatives like almond milk.

The deal is the second potential takeover in the food industry in recent weeks, following Mondelez International Inc's advance toward Hershey Co, which the chocolate maker snubbed.

"A potential takeout of the company has been part of our investment thesis since its spinoff from Dean Foods four years ago," wrote Christopher Growe, an analyst at Stifel Financial Corp. "It is likely this potential transaction further fuels the acquisition speculation gripping the food stocks, pushing multiples even higher."

The WhiteWave purchase, to be funded through debt, will boost results in the first year after closing, the French maker of Activia yogurt said.