A special enzyme, lipase, found in the olive fruit, acts lipolytically specifically on positions 1 and 3 of triglycerides and results in the production of free fatty acids (responsible for the acidity of olive oil).
Factors that affect acidity:
Olive oil acquires higher acidity when:
Olive oil acquires lower acidity when:
Peroxide are chemical compounds created by the effect of oxygen in the olive oil. The number of peroxides is due to hydroperoxides, which are products of the primary stage of oxidation of the unsaturated fatty acids of triglycerides.
Enzymatic oxidation is due to the action of lipoxidases, enzymes present in the olive. When the olive oil is separated from the wastewater in the mill, these enzymes, which are water-soluble proteins, are removed with the wastewater. In this way the olive oil ceases to be subject to the action of the enzymes. Chemical oxidation takes place during the preservation of the olive oil through a free radical mechanism.
The application of proper agricultural practices during cultivation and harvesting, the observance of proper storage practices, as well as the application of proper industrial practices throughout the olive oil production process at the mill, promote the production of low peroxide olive oil.
Lipoxidase enzymes act oxidatively as long as there is contact between the oil and the wastewaters, either because the cells have been broken during harvesting and storage or during breaking and milling operations.
Lipoxidase activity varies with temperature, but these enzymes are active even at -40o C. Chemical oxidation is favoured by light, high temperature, the presence of oxygen, and metallic elements. High peroxides indicate that the olive oil has undergone radical oxidative or other deterioration and are associated with a reduction in shelf life. Determining the concentration of peroxides therefore allows us to draw conclusions about the age and type of storage (under appropriate or inappropriate conditions) of the olive oil.
The spectrophotometric examination in the UV is the absorptions at wavelengths of 232nm and 270nm, conventionally represented by K. The IC index is defined as a mathematical relationship for calculating UV absorption coefficients.
The value of the absorption coefficient K270 depends on how fresh the olive oil is. Old olive oil or blends with old olive oil have increased K270 values. In addition, the value of K270 is very low immediately after bottling and increases with the age of the olive oil. Exposure of the olive oil to sunlight or high temperatures accelerates the progress of ageing
Taking into consideration the fact that the substances responsible for ultraviolet absorption (as a quality criterion) are products of oxidative reactions, it is obvious that air, light, temperature and traces of metallic elements are factors that affect ultraviolet absorption.
Therefore, prolonged storage of olive oil must be avoided and care should be taken during storage to ensure that the olive oil:
Organoleptic evaluation is the detection and description of the qualitative and quantitative olfactory-tasting characteristics of virgin olive oil using the human senses and its classification according to its organoleptic characteristics.
The method uses a group of tasters selected and trained and is applied only to classify it according to the perceived intensity of the defect perceived with the greatest intensity and the presence or absence of fruitiness.
The substances responsible for the negative organoleptic properties are not present in good quality olives. These substances are secondary products of oxidation or enzymatic reactions.