The essence of refrigeration is the transfer of heat from the body being refrigerated to some other place. The most obvious winery application of refrigeration is in the temperature control of fermentation—although refrigeration also allows winemakers to delay the processing of freshly picked grapes or must (see must chilling) until convenient, even in hot areas, where the use of chilled rooms to cool and store grapes prior to pressing has increased. The energy generated by the conversion of sugar to alcohol, carbon dioxide, and water is only partly used by the yeast in building cells and by-products. The rest appears as heat, which, above a certain temperature, risks killing the yeast and therefore arresting the fermentation process. The amounts of heat generated by fermentation are large. Ten hl/260 gal of grape juice containing 20% sugar will generate about 3.6 million kilocalories, or enough to melt 45 tons of ice.