Why do we do Achamanam (sipping water in driblets ) before and after eating food?

Before eating food, sipping  some small quantity of water around the platter of leaves, ( or these days plates)  and then by saying Amrutamastu ( which will become  nector) and taking inside  some little water and  then recall Yamadharmaraja, Chitragupta and other Deities and leaving the little Annam  (cooked rice)  at right side and eating their food is called Achamanam These customs  are  being prctised  very sacredly and devotionally. Ofcourse in this system there is one secret  also.

Sipping the water around the plates or platter of leaves , means the many  unvisible insects should not  be entered  into the food. And also once if that Achamanam is over , then  one kind of  protected  armour will form and stop those inesects.  Once, after eating food by doing again the Achamanam the protected armour will be cleared and the insects can go on their own way. This is the reason for doing Achamanam  at the time eating.