EFFECT OF EXTRACTION SYSTEMS ON QUALITY CHARACTERISTICS OF EXTRA VIRGIN OLIVE OIL

摘要

The influence of extraction systems (press, two- and three-phases) on the quality of olive oils extracted from two olive oil varieties (Coratina and Koronakii) was studied. Refractive index (RI), free acidity, peroxide value, specific coefficients of extinctions (K232, K270 and ΔK), natural antioxidant content, fatty acids composition, oxidative stability and antioxidant activity were determined as well as sensory analysis was done. From the obtained results, it could be noticed that there were no significant differences among olive varieties and extraction techniques in view of oils values; refractive index and unsaponifiable matters which appeared to be approximately the same. Also, results observed that there were slight differences in fatty acids composition, depending on the extraction technique and varieties employed. While, revealed that the extraction systems had significant effect on most chemical characteristics and oxidative stability of oils due to the differences in their natural antioxidants content which was higher in oils extracted by the two-phases and press systems than in that extracted by three-phase system. The sensory evaluation and the overall quality index indicated that olive oil obtained by two-phase system was the preferable among other oils obtained by press and three-phases; it received significantly the highest scores in all the judged quality attributes. Also, the total polyphenols were higher in the extra virgin olive oils obtained by the two-phase and press systems than in that obtained by three-phase system because the former two systems do not require the addition of water to olive paste in the decanter whilst, in the three-phases system water must be added to olive paste. The data revealed that the best extraction system was the two-phases system which produced high quality olive oil with high content of total polyphenols and that made it more resistant for oxidation during storage. Results also showed that Coratina variety gave oil with higher resistant to oxidation and higher sensorial score than oil extracted from Koronakii variety.