One of Napa County’s largest grape crushers is trying to determine how much wine was tainted and potentially ruined by a production accident at its facility in Oakville, according to winery sources.Napa Wine Co., which annually crushes 7,000 tons of grapes for more than 60 wineries, apparently contaminated some wine with cleaning detergent, according to a source informed of the accident.The company declined comment Wednesday. “We’ve got nothing to say,” said Kristi Koford, production winemaker at Napa Wine Co. “I don’t think it’s anyone’s business.”