Lactose in milk is important as
· It is essential for the production of fermented dairy products (cheese and yogurt) as it acts as a growth substrate for lactic acid bacteria.
· It contributes to the nutritive value of milk (although some people cannot metabolise lactose, a condition called lactose intolerance, see below).
· It influences the texture of frozen dairy foods (especially ice cream).
· It can become involved in the Maillard reaction leading to browning and the production of flavour compounds. (Browning of dairy products is often a defect.)
Lactose is a disaccharide of galactose and glucose linked by a b1-4 glycosidic bond. Its systematic name is b-O-D-galactopyranosyl-(1-4)-a-D-glucopyranose (a-latcose) or b-O-D-galactopyranosyl-(1-4)-b-D-glucopyranose (b-latcose). Lactose is a reducing sugar and may exist in two anomeric forms (a- or b-lactose).