Determination of α-tocopherol by reversed-phase HPLC in feed and animal-derived foods without saponification.

ABSTRACT

BACKGROUND: The analysis of α-tocopherol in feed and animal-derived foods usually involves a saponification step. However, since saponification often leads to losses of α-tocopherol, a method for the determination of α-tocopherol in feed and in animal-derived foods was developed without a saponification step. RESULTS: In this method, α-tocopherol is extracted with hot ethanol and the co-extracted fat is removed by centrifugation. Removal of the fat fraction is made possible by the addition of water, to achieve an ethanolwater ratio of 407, followed by cooling on ice before centrifugation. This procedure allows removal of the fat fraction, while α-tocopherol is retained. Matrices differing in gross composition and α-tocopherol content were analyzed fresh pork, cooked ham, subcutaneous fat, liver, egg yolk, milk and a compound pig feed. Higher α-tocopherol concentrations were found for this novel method compared to a conventional method with saponification, particularly for subcutaneous fat (P < 0.05). Recoveries were higher (P < 0.05) for the novel method (82-103%), compared to the saponification method (66-90%; for subcutaneous fat < 25%). CONCLUSION: Determining α-tocopherol in feed and animal-derived foods using pure ethanol without saponification results in higher extraction yields and recoveries compared to the saponification method.