3. lamp olive oil >2,0
4. refined olive oil < 0,3
5. olive oil composed of refined olive oils and virgin olive oils < 1
In olive oil you can detect a high acidity level when the product has been obtained from
olives fallen down and left on the ground long enough to trigger fermentation
phenomena with release of fatty acids. The souring is due to the release of fatty acids
from triglycerides by lipase. This is an hydrolytic process, which requires the presence
of water molecules, so all oils should be accurately separated from the aqueous phase.
The reaction used for the titration is a neutralization reaction.
Acidification reaction:
CH2-O-COOR CH2-OH
| |
CH -O- COOR’+ H2O → CH -O- COOR’ + R-COOH
| | fatty acid
CH2-O-COOR” CH2-O-COOR”
Triglyceride Diglyceride
For this we determined such a value in oil samples from different areas (the olives were
harvested in October and November):
4 samples, from the area of Molino d’Era, present an acidity value between 0.45% and
0.5%.
2 samples, from the area of Santa Margherita, present an acidity value between 0.3%
and 0.35%.
2 samples, from the area of Val di Cecina, present an acidity value between equal to
0,39 %.
In order to find the degree of acidity of the olive oil we used the operating procedure
based on the neutralization titrations.
Reaction involved in the titration:
R-C-OH + Na+ +OH- → R- C – O- Na + H2O
|| ||
O O
Determination of the acidity of the olive oil
Principle of the method:
The determination of the degree of acidity is based on titration of the solution of oil
through an aqueous solution of NaOH (weak acid-strong base titration). Being a weak
acid titration, the indicator used is the phenolphthalein.