Foods are classified into three groups based on ease of their spoilage.
Relatively stable or non-perishable foods: Foods that do not spoil unless handled carefully. E.g. grains, flour, sugar, pulses etc.
Protectable or semi-perishable foods: Foods those remain unspoiled for a fairly long period if properly handled and stored. E.g. potatoes, apples, onions etc.
Perishable foods: Foods that spoil readily unless special preservative methods are used. E.g. milk, eggs, meat, fish, poultry, most fruits and vegetables.