An independent advisory firm has given its stamp of approval to the offer by Dole Food Co. Chairman and Chief Executive David Murdock's to take the company private for $13.50 a share. Institutional Shareholder Services (ISS) issued a report recommending that Dole shareholders support the merger. ISS, owned by New York investment firm MSCI Inc., is a leading firm that advises investors how to vote on corporate issues. The Oct. 16 report cited the "meaningful premium" Murdock offered to buy the Westlake Village produce company. The $13.50 offer represented a 32 percent premium over an initial $12 a share offer in June. The offer values the company at roughly $1.6 billion, including debt. Murdock already controls 40 percent of the stock. The deal was unanimously approved by the company's board of directors, but is still subject to approval by a majority of shareholders not affiliated with Murdock. Stockholders are scheduled to meet on Oct. 31 to decide on the offer.