
Frank T. answered 04/30/19
Ph.D. in Film & TV Studies (UCLA) with 35 years of Teaching/Publishing
The answer is "it depends." If the script requires actual chewing, the performers will be required to eat the food, take after take. They may not have to swallow the food each time, though. Usually there's a convenience garbage can right below the camera's range (under the table, for instance) so that the actor can spit out the undigested meal.
After all the takes of the performer putting the food in his/her mouth are completed, then they may move in for one close-up of the person chewing and swallowing the morsel.
Actresses (and some males) are concerned about their weight and their diet, so corners are cut to prevent them from having to scarf down a dozen hamburgers in one sitting. The techniques I mentioned are often used, and sometimes veggie burgers and other substitutes are used.
Drinking alcohol on set is also frowned upon;generally speaking, ginger ale or sparkling cider can substitute for champagne and iced tea is often used for liquor.