Vacuum cooling is a rapid cooling technique for any porous product that has free water and uses the principle of evaporative cooling. Vacuum cooling is generally used for cooling food products that have a high water content and large porosities, due to its efficacy in losing water from both within and outside the products. (Lettuce is an example of vacuum cooled products.) This is the most widely used technique for rapid cooling of food products which has been proven to be one of the most efficient and economical methods of cooling and storage of vegetables, fruits, flowers, and more.