The effects of harvesting on phenolic compounds and fatty acids content in virgin olive oil (cv Roggianella)

THIS WORK IS A STUDY ON CHEMICAL CHANGES THAT OCCURRED IN VIRGIN OLIVE OILS (CV. ROGGIANELLA), PRODUCED FROM DRUPES HARVESTED AT SEVERAL PHASES, FROM OCTOBER 2006, TO JANUARY 2007. THE RESULTS OF THIS RESEARCH HAVE DEMONSTRATED THE TRENDS OF SECOIRIDOID AGLICON CONSTITUENTS OF THE VIRGIN OLIVE OIL WHICH RESULTED FROM TWO MAIN PRECURSORS GLYCOSIDE COMPOUNDS: OLEUROPEIN AND LIGSTROSIDE AND THE EVOLUTION OF THE FATTY ACIDS IN SIX STAGES OF RIPENING OF OLIVES. ANALYSES REPORTED AN INCREASE OF ACIDITY TO A VALUE OF 3.5 G % OF OLEIC ACID IN THE SAMPLE HARVESTED IN JANUARY. PEROXIDE VALUE GENERALLY DECREASED OVER TIME TO ACHIEVE 2.7 MEQ O2/KG AND TOTAL PHENOLIC CONTENT ALSO DECREASED FROM 579 TO 111 MG OF GALLIC ACID/KG OF OIL. THE HIGHEST QUALITY OIL WAS THAT OBTAINED FROM DRUPES HARVESTED ON THE FIRST THREE DATES, WITH 29.3 AND 38.7 HOURS AS RESULTED IN THE RANCIMAT TEST. STUDIES ON THE EVOLUTION OF PHENOLIC COMPOUNDS IN THE SAMPLES SHOWED MAXIMUM CONTENTS OF DIALDEHYDIC FORM DECARBOXYMETHYL OLEUROPEIN AGLYCON AND DIALDEHYDIC FORM DECARBOXYMETHYL LIGSTROSIDE AGLYCON IN DRUPES HARVESTED ON THE SECOND DATE (52.6 AND 13.9 MG/KG RESPECTIVELY). HYDROXYTYROSOL AND TYROSOL ALSO INCREASED DURING RIPENING WHEREAS IDENTIFIED LIGNANS (1-ACETOXYPINORESINOL AND PINORESINOL) DECREASED, THE FIRST FROM 24.5 TO 0.8 MG/KG, THE SECOND FROM 52.5 MG/KG TO TRACES IN THE LAST ANALYZED OIL. OTHER STUDIED COMPOUNDS WERE: VANILLIC, P-COUMARIC, 4-HYDROXYBENZOIC, O-COUMARIC, FERULIC AND CINNAMIC ACIDS, LUTEOLIN AND APIGENIN. WITH REGARDS TO 4-HYDROXYBENZOIC ACID AMOUNTS, THEY DECLINED DURING OLIVE RIPENING; THERE WAS, INSTEAD, A RISE OF FLAVONOID CONCENTRATION WITH A MAXIMUM OF 5.9 MG/KG. THE EVOLUTION OF FATTY ACID COMPOSITION WAS ALSO STUDIED DURING THE MATURATION PROCESS. IN THE EXTRACTED OILS A SIGNIFICANT LOSS OF SOME SATURATED FATTY ACID (C16:0, C18:0, C24:0) AMOUNTS WAS OBSERVED BESIDES AN INCREASE OF SOME UNSATURATED FATTY ACIDS (C16:1, C18:1, C18:2). THE RATIO BETWEEN MONOUNSATURATED FATTY ACIDS AND POLYUNSATURATED ACIDS DECREASED FROM ABOUT 29% IN THE FIRST SAMPLE TO ABOUT 26% IN THE LAST SAMPLED OIL. THE OLEATE DESATURASE ACTIVITY INDUCED THE LOWEST RATIO OLEIC/LINOLEIC ACID IN THE 5TH AND 6TH SAMPLES WITH A VALUE OF ABOUT 32%.