AOAC Official Method 939.02 Protein (Milk) in Milk Chocolate Kjeldahl Method
First Action 1939
Final Action
(Not applicable to chocolate products containing milk protein which has been subjected to high heat treatment.)
Weigh 10.0 g finely divided milk chocolate into 250 mL or larger centrifuge bottle and extract twice with ca 100 mL ether by shaking until uniform, centrifuging, and decanting ether layer each time.Place in bottle 2-hole stopper carrying bent glass tube, and straight glass tube that extends into bottle ca 1 3 of way to bottom. Expel ether by applying suction to bent tube and drawing moderate air current through bottle while it is in moderately warm (not hot) place. When ether is expelled, pipet 100 mL H2O into bottle. Stopper, and shake vigorously 4 min. Pipet in 100mL1%Na2C2O4 solution (w/v). Stopper, and shake vigorously 3 min. Let stand ca 10 min and again shake 1–2 min. Centrifuge ca 15 min at high speed (ca 1800 rpm).
