Discussion on the objective evaluation of virgin olive oil bitterness

The study aims at investigating the suitability of absorbance at 225 nm as an objective means to evaluate virgin olive oil (VOO) bitterness. Calculation of oleuropein score (OLS) using a standard curve instead of the so far employed K 225 value is proposed and a “taste index” based on the total phenol content determined by fluorimetry is examined as a complementary tool. Data from sensory evaluation of a series of VOO samples and RP-HPLC determination of phenolic compounds using diode array, fluorimetric or MS detection supported the applicability and merits of the introduced criteria. Phenol profiling using fluorescence detection (280 nm excitation/320 nm emission) became useful regarding oil bitterness. The presence of the non-fluorescent elenolic acid at 225 nm, indicated that the K 225 value is influenced by the presence of this non-bitter compound found at significant levels even in fresh oils. Our finding offers further ground to our proposal for the calculation of the “taste index”.