Determination of extra virgin olive oil acidity by FIA-titration

Abstract

Abstract A direct determination of extra virgin olive oil acidity by an automated flow injection titration is proposed. The oil sample (280 μl) is directly injected, without dilution, in the carrier stream, a n-propanol solution flowing at 2 ml/min and containing potassium hydroxide 1 mM as titrant and phenolphthalein 5 10−5 M as indicator. In the mixing chamber (1.5 ml) the sample mixes and reacts with the carrier stream. By an optical fiber beam, connected to a spectrophotometer set at 562 nm, we are able to appreciate continuously the phenolphthalein absorbance (Abs) decrease. The area of the peak “ΔAbs vs. time” has a linear correlation with the logarithm of the sample acidity. Several extra virgin olive oil samples have been analysed. The correlation curve between the official (O) and proposed methods (P) is P=(0.02±0.02)+(1.02±0.03)O, with r2=0.997 and sr=0.033; the accuracy and precision, expressed as mean error and RSD, are both