###### Abstract  
Virgin olive oil is inevitably subject to an oxidation process during storage that can affect its stability and quality due to off-flavors that develop before the oil surpasses its 'best before' date. Many parameters are involved in the oxidation process at moderate conditions. Therefore, a multiparametric study is necessary to establish a link between physico-chemical changes and sensory quality degradation in a real storage experiment. In this context, a storage experiment of 27 months was performed for four monovarietal virgin olive oils, bottled in transparent 500-mL PET bottles and subjected to conditions close to a supermarket scenario. Volatile composition, quality parameters and phenolic compounds were determined monthly. Simultaneously, an accredited sensory panel assessed their sensory characteristics. The stability of the fresh samples was also studied with the oxidative stability index (OSI) and mesh cell-FTIR. (_E_)-2-hexenal, (_Z_)-3-hexen-1-ol and (_E_)-2-hexen-1-ol were identified as markers of the fruity attribute. Hexanal and nonanal were also identified as compounds that were associated with the rise of median of defect during storage. Some disagreements were observed between the sensory assessment and the OSI analyzed by [PERSON]. However, the increase of concentration of rancid markers agreed with the increase of aldehyde band measured with mesh cell-FTIR. virgin olive oil; volatile compounds; sensory assessment; storage; SPME-GC; oxidation; oxidative stability; mesh cell-FTIR +
Footnote †: journal: Medical  
control-testing and information declared on the label. This is the case of some extra virgin olive oils that--after a storage period--may be unexpectedly downgraded to virgin olive oil category. For this reason, regulatory bodies have stablished some specific requirements concerning the storage conditions of olive oil [12; 13]. Additionally, International Olive Council has recently approved a document with the best practice guidelines for the storage of VOO [14]. The need of a major control of VOO stability is not new, although the increasing importance of sensory quality of this product and the stricter standards today [15] have encouraged producers and standardization bodies to find new methods to evaluate and understand VOO stability. Some methods are based on the study of the quality parameters during oil storage under conditions that are similar to real ones. These methods require a long period of study (several months), so they are not useful when a rapid answer is required. Other methods use accelerated conditions to obtain results in a shorter time (i.e., several hours/days), such as Rancimat, but they accelerate the oxidation process by means of drastic conditions and the results do not correlate well with the real oxidation process and do not take photooxidation into account [7]. Several studies have proposed rapid methods that assess VOO stability under conditions that are close to the real ones. Thus, Schaal oven test allows determining stability of the oils at 63 \({}^{\circ}\)C [16]. Other techniques, such as electron spin resonance spectroscopy [17; 18] and differential scanning calorimetry [19], have been also used to assess oil stability at 70 \({}^{\circ}\)C or lower temperatures. Recently, our group developed a new procedure based on mesh cell-FTIR spectroscopy [6] to assess VOO stability at room temperature considering the effect of photooxidation [7; 20]. The methods that use moderate conditions provide information that is easily correlated with the real degradation taking place in VOO under real storage. However, the interpretation of results is hindered by the fact that many parameters (chemical, physico-chemical, sensory) are evolving at the same time with different kinetics. Thus, it is difficult to establish a simple rule based on these parameters to assess if an oil is clearly out of the 'best before' date for its consumption.