Supervisors info:
Προεστός Χαράλαμπος, Επίκουρος Καθηγητής, Χημείας, ΕΚΠΑ
Summary:
This thesis is carried out as part of the postgraduate program of “Food Chemistry” of National and Kapodistrian University of Athens, and is also a part of the research program for the promotion of olive oil and olive products of the North Aegean Islands, through their bioactive content and their unique quality characteristics.
The goal of this thesis is the elevation of the olive products derived from the North Aegean, with the evaluation of their quality characteristics and their development through the passage of time.
This thesis studies the stability of an extra virgin olive oil under different storage conditions. Specifically, the sample was stored for a period of six months at two different temperatures, of 25°C and 4 °C, respectively. A quantity of the sample was filtered with a patented method and was stored at the respective conditions, resulting into 4 final samples. Several chemistry analysis techniques were applied at four periods, initial time (T1), after 1 month (T2), after 3 months (T2), and after 6 months (T3). The analyses conducted included acidity (through free fatty acids method, FFA), peroxide value, K232, ΔK, the determination of pigments and tocopherols by applying high resolution liquid chromatography with diode array detector (HPLC-DAD), the determination of 1,2- and 1,3- diglycerides and the determination of fatty acids methyl esters (FAMES) by applying gas chromatography with flame ionization detector (GC-FID), and the determination of phenolic bioactive compounds by applying Ultra-high performance liquid chromatography with negative electrospray ionization coupled with quadrupole time of flight mass spectrometry (UHPLC-ESI-QTOF-MS/MS). Also an organoleptic assessment was performed by an external laboratory. The performed analysis, took place on 4 time points, in order to evaluate the effects of temperature in a six-month storage period on extra virgin olive oil.
After the 6-month study, some changes in the quality parameters of the samples were observed. There was a small increase of the acidity and the peroxide value of the sample. Also, the constants K232 and ΔΚ had shown an upward course over time. As it was expected, there was a decrease in both the pigments of the sample and the tocopherols. The phenolic content also suffered a decrease in the course of time. The 1,2- diglycerdis to 1,3-diglycerids ratio decreased. The FAMES were not significantly affected. The
organoleptic assessment has shown a decrease of the quality characteristics for all the samples.
In conclusion, there was a significant difference on all the quality characteristics between the two samples (Control and patented sample). There were minor changes in the patented sample’s characteristics, opposed to the Control sample’s. Furthermore, the samples that were stored at 4°C showed less significant changes in the characteristics analyzed, proving that the storage of olive oil in lower temperatures helps maintain its quality longer.
Keywords:
Stability of extra virgin olive oil, stability, deterioration, phenolic compounds, organoleptic assessment.
