Two studies demonstrated that milling olive leaves with the olives improved the oil’s sensory attributes in industrial and small-scale experiments.
A new study confirmed that under certain conditions, the addition of olive leaves in the olive extraction process might enhance the overall polyphenol content and sensory profile of the resulting extra virgin olive oil.
According to the research published in Food Chemistry, the combined extraction of olives and olive leaves in a laboratory environment introduced chemical and organoleptic changes to the extra virgin olive oil, which are different from those previously observed in an industrial setting.
“We began working by modifying specific parameters of the extraction process, such as temperature, time, addition or not of water,” Ítala Marx, a researcher at the Instituto Politécnico de Bragança and University of Porto and co-author of the research, told Olive Oil Times.
“The following step was to co-extract olive oil with natural sources of phenolic compounds,” she added. “In this study, we analyzed the impact of the addition of 1 percent fresh olive leaves, co-extracted with Arbequina olives.”
The researchers decided on adding 1 percent of fresh olive leaves after observing that a small but undefined quantity of leaves ends up in the extraction process in most large-volume milling operations.
“From there, our team wanted to investigate what actually happens to the olive oil when such incorporation happens, in terms of sensory attributes, quality parameters, phenolic contents, volatile compounds,” Marx said.
The results of the experiment, which was conducted using a small-scale Abencor system, show that the resulting olive oil offers a significant improvement in sensory attributes — but reduced polyphenolic contents and volatiles — compared to olive oil produced solely from olives without the presence of any leaves.
However, previous research from the same academic team in an industrial setting demonstrated an improvement in sensory attributes and an increase in polyphenols, compared to olive oil produced solely from olives without the presence of any leaves.
“We attribute such different results to the different conditions of the two studies,” Marx said. “In an industrial setting, for instance, we were able to control operating temperature during the malaxation process, set at 22 ºC for 45 minutes, while in the lab setting, we had a 30 °C temperature during the malaxation process. And we also had different operational times.”
“In the industrial-scale research, with the same percentage of fresh leaves added to the process, we obtained olive oil which is rich both in phenolic contents than in volatile compounds,” she added. “In the Abencor laboratory-scale research, we have seen that olive oils extracted without leaves would have maintained a higher amount of the main phenolic contents, which did not happen on the industrial scale research.” More