Detection of the addition of Citrus reticulata and hybrids to Citrus sinensis by flavonoids

In some European countries there is a legal barrier against the marketing of some citrus juice mixtures under the denomination ''orange juice'', as allowed under certain conditions by the FDA for pasteurized and canned orange juice and for frozen concentrated orange juice. For this reason methods have to be developed to determine a juice addition of up to 10% Citrus reticulata and hybrids thereof and up to 5% Citrus aurantium. Using HPLC equipped with a photodiode array (PDA) detector we could establish that a combination of the flavanone glycoside (FG) and polymethoxylated flavone (PMF) pattern offers possibilities. For the flavanone glycosides the method is based on the presence of some specific compounds, on the didymin content, on a divergent ratio of hesperidin on narirutin, and/or on an unidentified component. In other cases, however, an F test applied on the relative PMF pattern offers a better solution calculating the % adulteration probability. We could conclude that, for all examined citrus samples added to Citrus sinensis, it is possible to detect the addition of 10% C. reticulata and hybrids thereof and of 5% C. aurantium.