Dear Ravi,
Lunch interval is the time granted to employees to finish their lunch as every human being normally does. You can not sub-divide the action of taking lunch into hand washing, drinking water,chewing and swallowing the food, occasional belching and the like and set timing step by step. If the time is not sufficient would you forego hand washing and drinking water?
However, though such being the practical aspects of lunch interval during the course of working hours every where, your question compels me to read in between the lines. May I presume that being a canteen diner, you are referring to the situation of poor and slow service in the canteen that cost your actual lunch break while your shift-in-charge has some uncompromising and strict time sense? If the actual problem is so, better make a representation to the canteen manager and the HR as well.