Study of the quality of Tuscan oil with CDR OxiTester for fast, simple and reliable analyzes in the oil mill

If in many respects 2020 was dramatic, at least from the point of view of “oil”, it reserved satisfactions for farmers and for operators in the sector in general: the quality of the oil released from the mills was excellent in general throughout Italy, while productivity was more contracted in the south and more abundant in the centre north.

The situation in Tuscany

In Tuscany in particular, the season was characterised by abundant and excellent quality production. The basically dry climate in summer prevented the proliferation of the oil fly.

The quality of the oil produced in Tuscany

As every year in the CDR Chemical Lab “Francesco Bonicolini” a small study was carried out on the main parameters of the oils produced in Tuscany using the CDR OxiTester analysis system.

In particular, more than 40 samples from various areas of Tuscany were analysed, determining the acidity concentration, the number of peroxides and the quantity of polyphenols.

The results of the analysis of the oil produced in Tuscany

Thanks to the generally dry summer climate, the acidity values were very low on practically all the oils tested.

The polyphenols have an average record of much higher values than last year, even if they were not at levels of “excellence”.

In particular, the average, regarding acidity, calculated on more than 40 samples, was 0.11% and no sample exceeded 0.2%. We are therefore talking about very low values. The average instead of polyphenols was 513 mg/kg against 424 mg/kg last year. The average value of peroxides was also particularly low, thus confirming an excellent quality level.

Below is the analysis table sorted by production date:

The climate and the quality of the oil produced

This year the climate has evidently had a positive effect on the quality of the fruits, significantly reducing the proliferation of the fly and allowing farmers to bring healthy, flawless olives to the mill.  As a result of these factors, the oils that have been analysed have a very high quantity of polyphenols.

To better understand the relationship between the climate and the quality of the oil produced, here is a summary of the data we have collected over the last 10 years in Tuscany.

In the last column of the table we have reported the millimetres of rain that fell in the areas of origin of the oils examined, in the months of July and August, in order to verify the relevance of this data with respect to the quality of the oil produced in the same year.

It can be stated that on average the quality levels are fairly high on fresh oils, except for 2014 which was disastrous for this sector.

Study of data relating to the ratio of rainfall/chemical characteristics of the oil

Here are two interesting graphs that show the annual relationship between rain in the summer months and polyphenols, in one case, and acidity in the other, of the oils produced.

The orange line represents the average acidity value and the blue columns represent the mm of rain in the summer months.

As can be seen from the graphs, the trend of the average value of acidity and that of polyphenols are closely linked to the rains: in the years in which the rains are lower, the polyphenol value is generally higher and the acidity lower.

In the 10 years examined, the absolute best from a qualitative point of view was 2017, the year in which rainfall was minimal (only 23 mm fell between July and August) and this undoubtedly contributed to having a very low average regarding the acidity parameter (0.11%) and a very high average value of polyphenols (560 mg/kg). Exactly the opposite of 2014 that everyone will remember as being a disastrous year for this sector and which recorded a rainfall record of 177 mm of rain in two months.  2019 was also not a year to remember qualitatively speaking.  The abundant rains had a negative effect above all on the value of polyphenols, recording an average of only 424 mg/kg.

Although varying with rainfall, the peroxide value was well below the limit set by law for the classification of extra virgin olive oil even in 2014, the worst year for quality from those examined. This parameter, important for the classification of the fresh oil product category, is certainly the most important to monitor during preservation of the product in the months following milling.


In the years examined (2011 – 2020) it is noted that when the summer rainfall is less significant, the polyphenol value is generally higher and the acidity value lower. Conversely, in the years when summer is rainier, the acidity value is high and the polyphenol value low. A high value of polyphenols and a low acidity value are an indication of high quality oil, therefore, in general, summers with little rain correspond to productions of better quality oil.