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Malaxation temperature for extra virgin olive oil

27 degrees cannot be an absolute parameter of quality. Defining a working temperature range is more correct, from a scientific point of view. Here is why

Based on the abundant literature on the topic, the optimal malaxation temperature range goes from 25 degrees up to 30 degrees (77 F to 86 F). Is it appropriate to malaxate at high temperatures? No. Is 27 degrees (80 F) and undisputed reference value to obtain a high quality olive oil? No.

It is necessary to distinguish between parameters related to the law and those linked to high quality. In the first case, the value of 27 degrees is a necessity. We would have better accepted a range of temperatures and not a precise value, but the necessity for compromises in Bruxelles makes it an impossible task. In the second case, 27 degrees is a false myth that only calls the attention of the producers.

“Nowadays, it is instrumental that quality becomes a measurable concept, based on scientific evidence – says Maurizio Servili, professor at the University of Perugia -. In order to achieve it, one parameter is not sufficient, it is necessary to build a system of certification of the weaving factory, based on the issues of production”.

Taking the parameter temperature into consideration, it is therefore impossible to assess precise limits. 27 degrees could be an even too high temperature for certain seasons and for advanced ripening. Similarly, as regards acidity for instance, threshold values are required by law, but categorically introducing inviolable bounds is not possible. A value above 0.3 is probably an index of management problems but celebrating a 0.29 oil while rejecting a 0.31 extra virgin would be senseless.

Therefore, it is worth reaffirming that malaxation temperature, as well as other factors, should be regulated in function of the olives, of the specificity and of the epoch of the production. The recent technological development of the last few years has significantly reduced the importance of temperature, in favor of a greater relevance of factors such as time and presence of oxygen, as Maurizio Servili confirmed to us.

“After the introduction of two-phases decanters, the most important technological development has probably been represented by the introduction of closed malaxation, that do not permit oxygen exchange with the outside environment, or under nitrogen. First of all, it is to be remarked that trials demonstrate that there is no significant differences, in terms of quality of the produced oil, between a full and closedmalaxation and a once operating under nitrogen, when the inert gas is reasonably utilized. Under both circumstances, the oxygen available to enzymes is sufficient to produce a good enough aromatic charge, but its concentration is too low to induce oxidative processes, which are strongly limited.

In absence of oxidation, the solubility of polyphenols in oil increases with time.
“With respect to the past, this is another major innovation. Studies carried out until the ‘90s, with open malaxation, demonstrated that the concentration of phenols in oil decreases proportionally to the time of gramolation. With malaxation that reduce the oxygen exchange, the opposite is true. In open malaxation, the oxidation of both the phenolic and aromatic components is as higher as the solubility of these compounds in oil increases with time, while the phenolic and aromatic charge increases when oxidative phenomena are limited.

How does temperature impact on this new context?
“With closed malaxation, temperature weighs on malaxation less than the control of olives dough oxidation and the duration of malaxation. Still, it remains an important parameter. It is worth recalling that an increase in temperature implicates a reduced aromatic charge, an alteration of the proportions among aldehydes, alcohol, esters. As the temperature progressively increases past 20 degrees, some enzymes are deactivated, past 30 degrees esters and alcohols begin to degrade, past 35 degrees esters, which are responsible for flowers and herbs aromas, disappear. Is it well worth excessively increasing the malaxation temperature in order to “extract” more polyphenols considering that, using closed malaxation, 300-400 mg (around 1 lb) of polyphenols are easily attainable?

In conclusion, “closed malaxation, permit a superior control of the temperature on the content in polyphenols and aromatic charge, by means of the regulation of time and presence of oxygen. It is basically a selective control, particularly useful if the producer, as it commonly happens, works with different olives, in different epochs of their ripping process.”

by Alberto Grimelli
06 april 2009, Technical Area > Olive & Oil