DALLAS — Net income at The WhiteWave Foods Co. in the third quarter ended Sept. 30 totaled $26,292,000, equal to 18c per share on the common stock, down 12% from $29,763,000, or 20c per share, in the same period a year ago.

Income from continuing operations also was lower, finishing at $42,271,000, which compared with $45,317,000 in the same period a year ago.

The company said results were bogged down by higher operating costs and expenses, which increased to $172,007,000 from $135,689,000 last year.

Net sales in the third quarter were $574,853,000, up 13% from $509,570,000 the same period a year ago. WhiteWave said the increase in sales reflected strong volume growth across the company’s North American segment, particularly in its Plant-based Foods and Beverages and Coffee Creamers and Beverages platforms.

Sales in the North American Plant-based Foods and Beverages business, which includes Silk Soymilk, PureAlmond and PureCoconut, increased more than 20% in the third quarter of fiscal 2012, WhiteWave said. Meanwhile, sales in Premium Dairy, which includes Horizon Organic branded milk and other products, increased mid-single digits on a percentage basis in the quarter.

WhiteWave, which is 86.7% owned by Dean Foods Co., completed its initial public offering on Oct. 31.

“Consistent with WhiteWave-Alpro segment results reported by Dean Foods on Nov. 8 as part of its consolidated third-quarter financial results, WhiteWave Foods continued to build on its momentum in the third quarter, delivering strong growth across the business,” said Gregg Engles, chairman and chief executive officer of WhiteWave. “We successfully completed the initial public offering of WhiteWave Foods Class A common stock and have hit the ground running. We are sharply focused on executing our business plans to continue to drive growth and are excited by the prospects ahead.”