The U.S. Food and Drug Administration (FDA) revised the food labeling regulations in 2016, to make the vitamin D content a required item on the nutrition or supplement facts labels for conventional food and dietary supplements. The change in labeling regulation is aimed to promote vitamin D awareness among consumers.
Recently, a new AOAC standard method which uses a derivatization reaction (PTAD) in the sample prep and a mass spectrometry in quantitation is available. This new method has provided much better analytical performance for vitamin D analysis than previous methods. However, previtamin D is not measured in this new standard.
Previtamin D is bioactive, and it is known that Vitamin D can thermally isomerize to Previtamin D. It has been reported that the relative content of previtamin D could be up to 22% of the total vitamin D at 80oC. Therefore, it is prudent to count previtamin D content in the analysis of vitamin D in foods.
This work proposes a new method in the determination of total vitamin D by individually measuring the vitamin D and previtamin D in food products.