I have been using this practice for quite sometime now and i find that by keeping everything in the classroom professional gives my students the sense of importance. While on the flip side encouraging them to have fun while they are cooking their food. Showing enthusiasm and praise for their efforts, especially when they follow your lead and cook delicious tasting food really makes you and the student feel good about themselves. I feel that by keeping your emotions in check goes a lot longer and you will receive more respect, but sometimes i feel that you have to show the opposite to let your students know that this type of behavior is not tolerated in the kitchen, IMO.