Concentration process increases the solids content and reduces the weight and volume of a food. Latent heat is transferred from the heating medium (steam) to the food to raise the temperature of its boiling point during evaporation. The vapour pressure rises and bubbles of vapour in the liquid are formed due to latent heat of vaporization supplied by the steam. The vapour is then removed from the surface of the boiling liquid. The more common concentrated foods include evaporated and sweetened condensed milks, fruits and vegetable juices and nectars, sugar syrups and flavoured syrups, jams and jellies, tomato paste etc.