With regards to the fermentable sugars,glucose and fructose are the main hexoses encountered in almost any natural must,being present in equivalent quantities in grape must,but the proportions may vary depending on the must fermented by each alcoholic beverage industry; nonetheless,the initial concentration of total sugars is approximately 100-250 g/l,with the lower fermentability of fructose providing the first challenge for saccharomyces cerevisiae yeast cells.