Degradazione dei composti fenolici durante la conservazione dell'olio extra vergine di oliva

Extra virgin olive oil is a particularly complex product. Controlling the relevant production chain requires a good knowledge of both transformation phenomena occurring in its chemical component and, as a result, functional changes in oil. During oil storage and distribution both non-enzymatic oxidative degradation of triglycerides and hydrolytic degradation of secoiridoids prevail, leading to the formation of hydroxytyrosol and tyrosol. The aim of this work was to follow the evolution during storage of secoiridoids and derivatives in different oil types, having different phenol contents and stored under different experimental conditions. During 2008, 2009, and 2010 oil crop seasons, olives from Frantoio cultivar were processed in an oil mill working in low oxidative impact conditions. Oil produced during 2008 and 2009 crop seasons was stored to simulate normal shelf-life conditions of products in a store. Oil produced during 2010 crop season was stored under specific conditions to accelerate degradation reactions. Legal quality parameters and phenol compound content were measured on olive oil samples by HPLC according to the COI method at both time zero and during storage. All the oil samples had a low acidity value and a similar oleic acid content. One out of three oil samples resulted to be different in bitter intensity and total phenol compound content. All the oil samples were subjected to low degradation, namely they showed a low parameter content, which was indicative of either oxidative degradation of triglycerides or hydrolytic degradation of secoiridoids. During storage trials, all the oil samples were subjected to significant degradation both in absolute terms and in relation to storage time zero. Results showed significance of compounds dialdehydic form of decarboxymethyl oleuropein aglycone (3,4 DHPEA-EDA) and hydroxytyrosol (3,4 DHPEA) as indicators of hydrolytic degradation of phenol compounds, the former being inversely related to degradation, while the latter was directly related to degradation. Our research demonstrated a protective effect of phenol compounds on autoxidation of triglycerides.