McDonalds

http://www.picturecorrect.com/tips/food-photography-tips-mcdonalds/

Above is a link to a video about how McDonald's go about their food photography. It is obvious that the product in the pictures and what you get in real life look completely different, this isn't due to major photoshop skills but by simple skills that make the product more appetising.

They start my using fresh ingredients like the bread for example, they use just out of the oven bread buns because they are more risen and haven't had time to be flattened. Then they bring all the fillings of the burger to the front so the consumer can see what they are getting in that particular item. They they add small touches like melting the cheese in certain places and syringe ketchup in where it's needed.