VPB 112: General Veterinary Biochemistry (1+1)

EXERCISE-11: ESTIMATION OF LACTOSE IN MILK (TITRIMETRIC METHOD)

Principle

• The aldehyde group of lactose reduces the cupric ions present in Benedict’s Quantitative Reagent (BQR) to insoluble cuprous hydroxide.
• Under mild alkaline conditions provided by sodium carbonate, cuprous hydroxide (yellow) on heating is converted into red cuprous oxide.
• Since, BQR contains potassium thiocyanate, a white precipitate of cuprous thiocyante is formed in the reduction process, instead of the usual red precipitate of cuprous oxide.