The molecule C12H22O11 forms a disaccharide structure composed of galactose and glucose. These two sugars connect via a specific β-1→4 glycosidic linkage to create the systematic name β-D-galactopyranosyl-(1→4)-D-glucose.
Whey contains 6.5% solids with 4.8% being pure lactose after milk curdles during cheese manufacturing processes. Industrial facilities filter whey permeate to remove major proteins before evaporating the remaining liquid to reach 60, 65% solid concentration for crystallization.
Most mammals reduce lactase production gradually as they mature past weaning stages because removal of dietary lactose eliminates metabolic pressure to maintain enzyme production. European populations maintain lactase persistence due to genetic selection over generations while less than 30% of people from African, Asian, or Oceanian areas retain this ability.
Lactose sweetness measures between 0.2 and 0.4 relative to sucrose at 1.0 while complete digestion yields 4 kcal per gram matching other carbohydrate values. Incomplete digestion ranges caloric value from 2 to 4 kcal depending on dose and it acts as dietary fiber when not fully broken down in intestines.
Italian physician Fabrizio Bartoletti published crude isolation methods in 1633 while Carl Wilhelm Scheele identified lactose as a sugar in 1780 during Swedish Academy proceedings. Jean Baptiste André Dumas named the compound lactose officially in 1843 and Emil Fischer established component sugar configurations by 1894 after years of research.