Lactose and sucrose both are disaccharides with molecular formula C12H22O11.Both have the same molecular formula but different chemical properties due to its structre because both of these lactose and sucrose are isomers of each other.Here are some of the differences between lactose and sucrose.

Lactose:

Lactose is a milk sugar, which is made up of the condensation of one molecule of glucose and one molecule of galactose.It is found in milk upto 5 percent.It is dextrorotatory.On hydrolysis, it yields one molecule of D-glucose and one molecule of D-Galactose.It is a reducing sugar because one of the aldehyde goup is free and that’s why it can form osazone.Lactosazone crystalls have hedgehog shape and these crystals are used for the identification of lactose in a solution.

Sucrose:

Sucrose is a common table sugar.It is a non reducable and made up form the condensation of one molecule of glucose and one molecule of fructose.As it is non resducible (both aldehyde and ketone groups are linked together), it doesn’t form osazones.On hydrolysis it yileds one molecule of D-Glucoser and one molecule of D-fructose.Its hydrolytic products are called invert sugar.

Differences between lactose and sucrose:

Lactose is a milk sugar while sucrose is a common table sugar.
Lactose is made up of glucose and galactose while sucrose is made up of glucose and fructose.
Lactose is hydrolysed by lactase enzyme while sucrose is hydrolyzed by sucrase/invertase.
Lactose is dextrorotatory while sucrose is also dextrorotatory but its hudrolytic products are leavorotatory.
Lactose exhibit mutarotation while sucrose doesn’t exhibit mutarotation.
Lactose is reducible sugar while sucrose is non-reducible sugar.
Hydrolytic products of lactose on treatment with HNO3 can form mucic acid while sucrose deosnt form mucic acid.
Lactose form osazone called lactosazone whose crystals are hedgehog shape while sucrose cannot form
Lactose give positive Fearon test while sucrose give Fearon test negative.
Lactose can be synthesised in lactacting mammary gland from glucose while glucose cannot.
In lactating mother lactose may appear in urine,producing lactoseuria while sucrose cannot.