The 2012 olive oil season in Tuscany proved to be of very high quality, in spite of the decrease in production in some areas. The prolonged summer drought certainly helped to minimise olive fly attack, so the oils produced this year are characterised by a particularly low concentration of acidity, as could be expected.
As we did last year, a brief study on the quality of Tuscan olive oil was carried out in the CDR chemical laboratory: 41 samples of extra virgin olive oil from various areas of Tuscany were analysed using our CDR OxiTester oil analysis instrument.
For each oil sample, we determined the values of acidity, peroxides and total polyphenols. The studies carried out in our laboratories have shown that this last parameter is the one that characterises the quality of fresh olive oil the most.
So, we have listed here below the results of the sample analyses in descending order according to the polyphenol value. As occurred in 2011, the quality of the oils analysed resulted to be excellent according to this specific parameter, but the olive oil season that is coming to an end also recorded high values of acidity and peroxides in the areas of origin of the samples, confirming a season that did not hold any bad surprises in terms of quality.
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The acidity concentration, averaging 0.11 % of oleic acid, really reached record levels, compared to previous years. Such low values were certainly indicative of a perfect health condition of olives as well as of the use of well-controlled harvesting and processing techniques.
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How do acidity, peroxides and polyphenols vary over a year of oil life?
A specific monitoring study on these three parameters (acidity, peroxides and polyphenols) was carried out on three samples taken during the 2011-2012 oil season in order to assess the trend of the values during a whole year of product life.
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The graphs demonstrate that the samples show a constant decrease in the value of polyphenols over time, whereas the increase in the value of peroxides is exponential. Acidity, as expected, did not significantly increase over the monitored period.
Taking into consideration the graph of the peroxide value trend over time, it can be noted that while sample 1 and sample 2 initially had approximately the same peroxide value, sample 2, which is richer in polyphenols, has a lower peroxide value compared to sample 1 at the last analysis.
However, the polyphenol trend failed somewhat to meet expectations. In fact, the difference between the peroxide value of sample 2 at the last analysis and the peroxide value of sample 1, which is less rich in polyphenols and therefore more subject to oxidation, is not as marked as might have been expected.
The three samples actually had a similar "deterioration" of antioxidant capacity and a similar increase of peroxide level. According to the data, though, sample 1, which had lower starting polyphenol levels, also showed a higher peroxide value and its exponential increase started earlier than the other two samples.
This leads us to the conclusion that, if stored correctly, protected from light and heat and with minimal contact with air, a sample with a high polyphenol value will retain important organoleptic characteristics even during ageing.