I read somewhere that children are generally open to a
variety of foods until about age 3, from which point on
they usually only eat what they're accustomed to eating
and are wary of new foods. After that point, they may
try new foods (and it will vary from one child to another)
but are often reluctant to try them or need time to
get used to them.

This is more so with animal foods
than plant foods. People will try new plants with
less fuss, but people (from age 3 up through
adulthood) tend to be reluctant to try new animal
foods, whether parts of an animal they're not
accustomed to eating (brains, kidney, etc.) or
animals they're not accustomed to eating (goat, rabbit, etc.)

There are good reasons why we have these instinctive
patterns. As babies we learn the foods that are
generally eaten in our culture, and then from age
3 on we mostly stick to those foods, with some
ability to adapt to new foods/new cultures if
necessary. In this way we tend to avoid eating
poisonous plants, or, even more dangerous perhaps,
diseased meats. With plants you can taste a bit,
maybe wait a few hours
and see whether you feel sick and have some chance
of avoiding dying from it, but if you're going to
pick up a disease from eating brain or something
that method won't save you.

Adults tend to be more open to new foods than
children from age 3 up to -- I don't know --
adolescence or something. but not as open
as 2-year-olds I think.