The two most common reasons I know for foods coming out whole is inability to digest it properly or not chewing it properly (which are really both related to one another).
FYI - I found this on
http://www.webmd.com about food intolerances and constipation:
Food intolerance is an adverse reaction, such as a stomachache, bloating, gas, or diarrhea, to certain foods.
Dairy products such as milk, ice cream, cheese, or yogurt can cause constipation when a child has too many servings in one day.
For children over 12 months add the following to promote regularity:
Add at least 2 servings of fruit, such as apricots, peaches, pears, raisins, figs, prunes, dates, and other dried fruits, each day.
Add at least 3 servings of vegetables, such as cooked dried beans or peas (legumes), broccoli, or cauliflower, each day.
Hope that helps!!!!