Automated Olive Oil Acidity Determination by Flow Injection
Olive oil samples are injected and dispersed in the 7.5 x 10-4 M KOH and 4.0 x 10-5 M phenolphthalein in n-propanol titrant while flowing through a mixer. The absorbance of the reaction mixture is continuously monitored at 562 nm, ëmax of the basic form of the indicator. The resulting negative absorbance peaks indicate the transition: base (red)-acid, (colorless)-base, (red)-acid of the indicator. This is a flow injection titration method so measurement of acidity degrees (AD, % w/w free fatty acid content expressed as oleic acid) is based on peak width (Ät) measurement:
Ät = a x Log(AD) + b
The analysis rate achieved is 30-100 samples per hour. Results obtained compare well with those obtained by the official method (0.3-3.6% relative difference for the analysis of 32 olive oil samples). Click to see the advantages of the method.
Questions and comments to author: Dr C.A. Georgiou, cag@aua.gr Phone: +3010-5294248, fax: +3010-5294265 Chemistry Laboratory, Agricultural University of Athens, Greece