Role of hydroxycinnamic acids and vinylphenols in the flavor alteration of blood orange juices

Free and total ferulic and p-coumaric acids were determined in two processed blood orange juices produced in Italy: one freshly squeezed and the other from concentrate. Hydroxycinnamic acids and their corresponding decarboxylation products, p-vinylguaiacol and p-vinylphenol, were also determined in the juices for up to 4 months of storage at 4 and 25 degrees C. The flavor threshold of authentic vinylphenols in aqueous solution and in the blood orange juice was evaluated by sensory analysis. Concentration of these off-flavors in the stored juices abundantly exceeded the threshold values, especially in the juice from concentrate. The content of vinylphenols might provide a reliable index of blood orange juice quality.