Rachael Ray got be one of the most trusted celebrities, essentially, because she is nice. It probably doesn't hurt that she is also cute and friendly, but if she wasn't as nice as she is, she wouldn't be as popular. In fact, people really like their celebrities to seem nice and friendly, with only a few exceptions. The number one exception, the scariest celebrity on TV, happens to be a chef as well: Gordon Ramsay. Ramsay is known for yelling, screaming and occasionally reducing people to tears on his TV shows Gordon's Kitchen Nightmares, Hell's Kitchen and the F Word. He not only has a bad-boy attitude on TV, but he defends the fact that it - treating other people as though they are completely incompetent idiots - is his true character and not just an act.
If you're curious as to which other celebs made the British list, they included Anne Robinson (#2, from The Weakest Link), Fanny Cradock (#5, one of the first celebrity chefs), and Simon Cowell (#10, from American Idol).