All of a sudden, mayonnaise is in the news. Kraft touts its "first-of-its-kind" Big Mouth jar, a 32-ounce shatterproof container with an opening double the size of the one on a regular jar. Spatulas and even measuring cups fit neatly into the jar, which is available in Real Mayo and Light Mayo. It's about $2.65 in supermarkets. Not to be upstaged, Best Foods has introduced Canola Real Mayonnaise, made with canola oil instead of the soybean oil usually used in bottled mayo. Canola oil is said to have a better fatty-acid profile, meaning it contains higher levels of monounsaturated fat...