Gregg Engles, chairman and chief executive, will take over responsibility for the dairy group, the company said.
Bernon, who has been with Dean for 10 years, headed the division that accounts for nearly 90% of Dean's revenue and nearly all its operating profit.
However, the dairy group, which sells milk under 50 company-owned brands as well as some retailers' store labels, has faced sour financials as the price that Dean must pay producers for raw milk has risen 75% from December to now -- hitting all-time highs.
Operating profit for the division fell nearly 9% in the second quarter, the company said earlier this month.
Company spokeswoman Marguerite Copel said Bernon is not leaving as a result of those challenges. He will remain on the board of Dean directors, the company said.
Bernon could not be reached for comment.
"There's never a good time for an executive to leave, but it does allow Gregg to get closer to initiatives and projects that are under way," Copel said.
From the September 10, 2007, Prepared Foods e-Flash