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.
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Peaks acquired during acidity   determination

Standards of
(a) 0.100, (b) 0.150,
(c) 0.277, (d) 0.400,
(e) 0.800, (f) 1.00,
(g) 2.00, (h) 3.00,
(i) 6.00, (j) 8.00 and
(k) 10.0 acidity degrees

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