A PepsiCo takeover Danone would be the biggest Franco-American upset since The Simpsons called the French "cheese-eating surrender monkeys" in 2003.

Speculation about such an offer sent Danone's shares to a mid-week high of €92.68 last week, valuing the French food group at €24.5bn ($29.5bn) against €21.5bn before the rumours intensified about PepsiCo's interest.