The definition of food preservation states that the preserved food should retain their colour and taste. This means that the colour and taste of food which is present at the time of preservation should not change. Let us take the example of preserving grapes as raisins. Raisins are prepared by sun drying grapes. During the drying process the grapes change colour from green to brown, and taste, sweeter However, once they are dried and stored, they do not change colour or taste.