AOAC Official Method 936.12 Oil (Tea Seed) in Olive Oil Qualitative Color Test
First Action 1936
Final Action
For preliminary qualitative test use following room temperature method: Measure exactly 0.8 mL acetic anhydride, 1.5 mL CHCl3, and 0.2 mL H2SO4 into test tube (18 ´150 mm is convenient). Mix, and cool to room temperature. Add 7 drops of oil to be tested directly to reagents, mix, and cool again. (To measure test oil, use glass tubing, 4mmod, and ca 2mmid; 7 drops should weigh ca 0.22 g.) If solution of oil in reagents is cloudy after mixing and cooling, add acetic anhydride dropwise, shaking after each addition until solution suddenly clears. Appreciable deviations from these amounts, particularly in H2SO4, cause distinct variations in color intensities. Since mixed reagent deteriorates slowly, do not mix in advance of testing. After 5 min, add 10 mL absolute ether from graduate and mix immediately by inverting once. Tea seed oil forms brown solution changing to intense red within min or so. This red reaches maximum and then fades slowly within few min. Olive oil forms initial green solution on addition of ether. This color fades slowly to brown-gray, occasionally passing through faint pink stage. Both olive oil and tea seed oil eventually fade to permanent light brown. Mixtures of tea seed oil and olive oil show characteristic tea seed oil colors proportional in intensity to amount of tea seed oil present.
