Spectrophotometric Determination of Protein and Fat in Milk Simultaneously

A completely clear solution was obtained by adding 5 ml of 97% acetic acid to 0.05 ml of whole milk.The protein was calculated from the absorbance at 280 m~.Turbidity depending on fat content was developed thereafter by adding 2.5 ml of a solution containing 20% urea and 0.2% imidazole.The fat was determined from absorbance at 400 m~ with a round cuvette.This method does not require prehomogenization of milk for turbidity measurement, because of a dispersing effect by the combination of reagents.Application of this method to other food products is suggested. Experimental MethodsReagents.Acetic acid diluted to 97 volume per cent; urea-imidazole solution, 20% urea, and 0.2% imidazole in water.Procedure.Add 5 ml of 97% acetic acid to 0.05 ml of milk in a test tube closed with a ground-glass stopper and shake to ensure complete solution.Measure the absorbanee at 280 m~ with a 1-cm cell against a reagent blank in a Beckman DB spectrophotometer.To this solution add 2.5 ml of the urea-imidazole solution, mix well and let stand for 30 minutes.Measure absorbanee at 400 m/z with a round ceil in a Spectronic 20 Bausch & Lomb instrument.