Formation of Anhydro-Sugars During Thermal Degradation of Lactose

Formation of glycosidic anhydro-sugars from heated lactose was studied. Anhydrohexoses were formed first by heating lactose in an open system. The 1,6-anhydro- β -D-glucopyranose and 1,6-anhydro- β -D-galactopyranose increased in proportion to glucose and galactose, which were also formed during short heating periods. Prolonged heating of lactose caused the amount of 1,6-anhydro- β -D-glucopyranose to exceed that of 1,6-anhydro- β -D-galactopyranose. Anhydro-disaccharide also was detected in the pyrolyzate of lactose. We speculated that the disaccharide was a reaction intermediate,4-0- β -D-galactopyranosyl-1,6-anhydro- β -D-glucopyranose, and contributed to formation of 1,6-anhydro- β -D-glucopyranose.