Question

to increase the shelf -life of food ,milk and others ,we either cook or boil our food items give reason

Answer 1

Cooking or boiling food increases the shelf life because the bacteria present in the food dies off from the heat.

It is a reliable way of conserving food but requires consistence. The food should not take long hours after the initial boiling  before being boiled again. The time span she be observed till the food is all consumed.

Answer 2

  We either cook or boil our food items to increase the shelf-life of food, milk and others why because heating at high temperature or boiling kill the food pathogens and bacteria so that we can preserve them for a long time.  

  As absence of this microorganism will not allow spoiling the foodstuff for a long time. Hence we should always boil or heat the foodstuff to preserve them.