Abstract
Filtration is the most widespread stabilisation operation for extra virgin olive oil, preventing microbial and enzymatic changes. However, during the harvest, the workload of olive mills is at its peak. This results in two approaches to filtration: (i) delays it until after harvesting, increasing the risk of degraded oil quality, and (ii) filters it immediately, increasing the workload. The aim of our experiment is to assess the risk of delaying filtration and establish a safe delay time. Changes in the sensory profile and volatile compound contents were evaluated during 30 days in filtered and unfiltered samples. Significant differences were related to filtration: both turbidity grade and microbial contamination; no differences for the legal parameters were found. Two, contrasting, results were obtained with respect to oil quality: (i) the fusty defect, appearing in less than five days in unfiltered oils, leading to the downgrade of the oil’s commercial category, and (ii) filtration removing some lipoxygenase volatile compounds. Consequently, a fruity attribute was more pronounced in unfiltered samples until day five of storage; it seems that, from this point, the fusty defect masked a fruity attribute. Hence, filtering within a few days strongly reduced the risk of degraded oil quality compared to a delayed filtration.
Highlights
Olive oil is composed of triacylglycerols, which make up over 98% of the total weight and about2% minor components—aliphatic and triterpene alcohols, hydrocarbons, sterols, non-glyceride esters, pigments, lipophilic and hydrophilic phenols, and volatile compounds [1].Volatile compounds are a complex mix of aldehydes, alcohols, ketones, acids, hydrocarbons, and esters and are closely associated with both oil flavour and its positive and negative sensory attributes [2,3]
The aim of this study is to assess the effects of the delayed depth filtration of veiled olive oil on volatile compound contents and the presence of sensory defects that downgrade oil from the “extra virgin” to “virgin” quality category. For this investigation, during the first month of storage in protective conditions, we have examined the kinetics of volatile compound contents, and sensory analyses, in immediately filtered olive oil samples and in the respective veiled olive oil samples, which would be hypothetically filtered after several days, as often happens during olive oil production
During the first month of storage, we examined the kinetics of volatile compound contents in immediately filtered olive oil samples and in the respective veiled olive oil samples, which would be hypothetically filtered after several days
Summary
2% minor components—aliphatic and triterpene alcohols, hydrocarbons, sterols, non-glyceride esters, pigments, lipophilic and hydrophilic phenols, and volatile compounds [1]. Volatile compounds are a complex mix of aldehydes, alcohols, ketones, acids, hydrocarbons, and esters and are closely associated with both oil flavour and its positive and negative sensory attributes [2,3]. Flavour is a key characteristic that affects consumer preferences [2,4], but it is a quality parameter in oil classification. In 1991, the European Commission laid down legal limits for many quality parameters, including sensory attributes [5]. The panel has to confirm the absence of sensory defects (median of defect equal to 0) and the presence of the positive, fruity attribute (fruity median greater than 0) in order to classify an olive oil as “extra virgin”. In particular, are described in the official sensory evaluation methodology: fusty, muddy, mustiness-humidity, winey-vinegary, and rancid
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