Jonathan Blum, public affairs chief for Yum! Brands, is retiring after 23 years with the fast food giant and its Taco Bell unit.

Jonathan BlumJonathan Blum

Blum was a Carter White House aide before moving to the agency realm in the mid-1980s with Ogilvy PR. He moved to Taco Bell a decade later as VP of PA and moved to Yum! when PepsiCo created the company with the spinoff of Taco Bell, KFC and Pizza Hut.

Blum, also held the title of chief global nutrition officer, is stepping down to devote more time to his craft beer company, Bad Martha Beer of Martha's Vineyard.

Yum! chairman and former CEO David Novak called Blum "the finest public affairs executive in the world and one of the best business leaders I know."

Blum said he wants to grow two-year-old Bad Martha Beer into a dominant regional microbrewery and a socially responsible business. The brand is sold in Massachusetts, Rhode Island, and is slated to launch in Connecticut.

Yum! credits Blum with "setting the standard" for CSR, including its large food and cash donation program with the United Nations World Food Programme.