Ralcorp Holdings will close a pair of plants in Dunkirk and Silver Creek, eliminating 375 local jobs just months before the St. Louis-based food company is set to be acquired by ConAgra Foods

Ralcorp said Thursday that it will close Carriage House Co.’s Dunkirk factory that makes private-label condiments and sauces, including salad dressing, table syrup and a variety of beverage mixes and syrups. The plant, which Ralcorp acquired in 2000 as part of its purchase of Red Wing Co., also makes seasonal grape pulp and juice.

It also will close Petri Baking Products, a Silver Creek facility it acquired less than a year ago that makes home-style cookies.

The work now done at the Silver Creek and Dunkirk operations will be shifted to other facilities within the United States as part of a “reallocation of manufacturing to maximize capacity and capabilities” at Ralcorp’s remaining plants. A company spokesman declined to discuss the closings.

Ralcorp, which has 40 manufacturing facilities across the country, will continue to operate Carriage House’s plant in Fredonia, along with Sugar Kake Cookie, a Town of Tonawanda plant that makes sandwich creme cookies for retailers such as Walmart.

Ralcorp acquired Petri Baking Products last May, with company executives saying Petri’s products complemented its own line of cookie products.

Workers at the two plants were notified Thursday of the shutdowns, which are expected to occur after the expiration of a 60-day notification period required by federal law.

ConAgra agreed to buy Ralcorp in November in a $5 billion deal that would make it the country’s biggest manufacturer of private-label foods and expand its position in the market for cereals, crackers and other packaged foods sold as store brands. That deal is to close by the end of March.