Provena Foods Inc. reported net earnings of $250,784 for the third quarter, the company's first report since its initial public offering on Aug. 20. The company earned $213,219 for the third quarter of 1986. Sales for the quarter were $8.7 million, up 24% from $7 million a year earlier. James Bolton, chief executive officer, said commodity costs continued to increase during the third quarter, causing some reduction in profit margins. Provena, based in Santa Ana, is a specialty food processor serving the pizza and pasta industries.