Adventurousness at a young age

There's no denying that we are all conditioned to have preferences. Things that are familiar to us and that we grew up with will usually be looked upon more fondly than something completely unfamiliar. I'm thinking specifically about food preferences. There's actual research somewhere that demonstrated that irrespective of how good or bad a cook someone is, the kids often look fondly back on "mom's cooking" and identify at least one dish that their mom made "perfectly" (even though others may not have found that dish to be particularly well made.)

Anyway, that's not my point. I wonder whether a person's open-mindedness to trying (and liking) new foods can be encouraged or adjusted during childhood. I noticed that my kids are generally quite dismissive of completely unfamiliar foods. I take them to a great restaurant in France and they are more likely to order hamburgers than goose liver paté. Sometimes, when I really egg them on, they'll take a small bite and immediately declare (before it has even been given a chance to rest on their tongue an instant), "I don't like it." The reason I started thinking about this was that I spent a few days in Italy with my brothers' kids (about the same general age as my kids). The 12-year-old was extremely adventurous in his choice of foods. At restaurants, he would order something that seemed quite unfamiliar (e.g., lamb cutlets milanese style) and attack these foods with great enthusiasm when they arrived at the table. Without any urging, he would ask his Dad what he had ordered and ask for a taste with a statement like "I wonder what that tastes like, can I try some?" He actually avoided the widely available pizza in Italy with a comment to the effect "Oh, that's too boring, I can get that anywhere" before ordering something more esoteric.

This came across to me as very mature and sophisticated and I wondered how I can wean my kids away from the burger and pizza approach to trying foods when away from home and get them to want to try new foods and make an effort to actually like them. That is, I want them to assume it must be good food if it is popular in the country they're visiting and assume they will like it unless consistently proven otherwise. Is there anything I can do to get them to actually develop a taste for unfamiliar foods?

If I find an answer, I'll try it on my wife too! :)