Largest group of organic compounds consisting of carbon, oxygen and hydrogen (the latter two mostly in a ratio of 2 to 1), which are produced in plants during photosynthesis by assimilation of carbon dioxide. They are the basic food and energy source for all organisms and in plants they are the structural substances. Important carbohydrates are above all the various types of sugar. In the case of the vine, carbohydrate reserves are an important factor for growth during the annual vegetation cycle. In autumn they are stored in the lignified part in the form of starch, in spring this is converted into sugar, which provides the energy for sprouting. During grape ripening, sugar is transported into the berries. The grape must contains carbohydrates in the form of glucose and fructose as well as pectins. See also under total extract.