Well like most things on the menu of life, it seems to vary from one patient to the next. Some people with Crohns can tolerate something well while the next patient reacts almost violently. As has been so often noted here, it's really trial and error -- and even then you may have to try something several times as a test, since lots of us also have flares for reasons that are not related to what we ate last. Just a suggestion, but you might try onion juice for flavoring, since that would clearly eliminate any consideration that his reaction could be to the bulk, texture or physical digestability.