Olive & Oil 01/04/2013

Everything you need to know on bitter in extra virgin

We must dispel some common myths, trying to give scientific rigor, perhaps through precise analysis, even the sensations. But our senses are elusive and complex

How do you get a bitter oil, with a high load of polyphenols? Of course it is necessary to mill green olives, which have a high content of these components in them, but we need to dispel a common place. The higher the temperature in grinding so you will have more phenolic extraction. This is the conclusion reached by the University of Perugia. The results show a positive correlation between the temperature and the concentration of derivatives of aglycones secoiridoids. Therefore been studied the effect of temperature on oxidoreductase that promote oxidation (polyphenol oxidase and peroxidase). While the peroxidase (POD) showed the highest activity at 37 ° C and a high stability at the temperatures, the polyphenol oxidase (PPO) showed the optimum at about 50 ° C, with the activity that already decreased to 40 ° C and a large variability due to the cultivar. A search that explains the functioning of the enzymes involved in the solubilization of polyphenols with consequent correlation between the activities of the two enzyme complexes and the concentration of phenols in the oil.

It is clear that neither the study nor Teatro Naturale recommend knead to such temperatures would produce significant and recognized negative side effects on oil, as the flavor of cooked, but they represent an important step in understanding the dynamics of these compounds during the extraction phase.

Yes, because it is already known that polyphenols are related to the bitter and spicy taste sensations in extra virgin olive oil. Having an idea of ​​the intensity of these feelings, which have a strong impact on the consumer, so as to influence the choices, it is certainly interesting. And 'well known that especially bitter is the feeling that, even within highly professionalized and homogeneous panel, gives the greatest discrepancies among the panelists. It follows that the assessment of the panel test, in this specific case, can be scarcely useful. Survey by the University of Bari, however, can come in handy. And 'in fact been discovered, of monovarietal oils of Coratina, Leccino, Maiatica, Ogliarola and its blend that is possible to correlate the intensity of the bitter with a chemical parameter, the K225. A simple spectrophotometric analysis, therefore, would be able to predict the intensity of the bitter an oil, providing useful information also for the blend.

Unfortunately or fortunately, however, our senses are more complex and attests to a study conducted by the University of Florence a few years ago. Already in the past studies on the sensory profile of olive oil have consistently revealed a relationship between the perceived intensity of "bitter" and ipiù precisely evaluated the influence of the smell of "freshly cut grass" intensity of perception of ' bitter oil, and the pleasantness of the oil. The results obtained indicate that both the duration and the intensity of perception of the bitter in an oil is positively affected by the smell of "grass". From the results of the University of Florence, therefore, it is clear that the excessive intensity of taste oil could contribute not only by phenolic substances but also from those birds, related to varieties, agronomic practices, stage of maturity and olive crushing and grinding technology.


G. Caporale, S. Policastro, E. Monteleone. Bitterness enhancement induced by cut grass odorant (cis-3-hexen-1-ol) in a model olive oil. Food Quality and Preference 15 (2004) 219-227
Fabio Favati, Nicola Condelli, Fernanda Galgano, Marisa Carmela Caruso, Extra virgin olive oil bitterness evaluation by sensory and chemical analyses, Food Chemistry (2013), 139, 949-954
Agnese Taticchi, Sonia Esposto, Gianluca Veneziani, Stefania Urbani, Roberto Selvaggini, Maurizio Servili, The influence of the malaxation temperature on the activity of polyphenoloxidase and peroxidase and on the phenolic composition of virgin olive oil, Food Chemistry (2013), 136, 975-983

di Alberto Grimelli