Study Finds Taste Tradeoff in Olive Leaf Infusions

New research has linked the phenolic content of olive leaf infusions to their sensory profile, shedding light on the challenge of balancing bioactive compounds with consumer preferences.

According to the authors of the research published in Food and Humanity, the sensory effects of different extraction methods have rarely been investigated. Previous studies have largely focused on maximizing the extraction of polyphenols and antioxidant compounds.

“We realized that obtaining a beverage with high antioxidant content would have little practical value if consumers were unwilling to drink it. Therefore, we wanted to understand the relationship between extraction efficiency, sensory characteristics and consumer acceptance,” Ignacio Vieitez and Cecilia Dauber told Olive Oil Times.

Olive leaves should no longer be regarded as waste but rather as a valuable raw material within a circular bioeconomy framework.– Ignacio Vieitez and Cecilia Dauber, University of the Republic, Montevideo, Uruguay

Vieitez is a professor in the Food Science and Technology Department at the University of the Republic in Montevideo, Uruguay. Dauber is a researcher at the same institution. Both contributed to the study.

To evaluate how extraction conditions affect the chemical composition and sensory characteristics of olive leaf infusions, the researchers prepared 12 infusions using Arbequina olive leaves grown in Uruguay.

The leaves were processed in three forms: whole, broken and powdered. Each was infused in water at either 75 ºC or 95 ºC for three or five minutes, creating a range of conditions designed to mimic domestic preparation methods.

The team analyzed each infusion for total polyphenol content, oleuropein concentration and antioxidant activity. At the same time, a 10-member trained sensory panel evaluated bitterness, astringency, green odor, green flavor, flavor intensity and persistence.

The results showed that leaf particle size had a greater influence than either temperature or infusion time.

Powdered leaves produced the highest concentrations of polyphenols and oleuropein, along with the strongest antioxidant activity. However, they also generated the most intense bitterness, astringency and green sensory notes.

Whole leaves produced much lower levels of bioactive compounds and milder sensory profiles. Broken leaves generally fell between the two extremes.

Based on these findings, the researchers selected two contrasting infusions for consumer testing. One hundred participants evaluated the products for acceptability and purchase intention, allowing the researchers to explore how sensory differences influenced consumer preferences.

“We expected that higher polyphenol concentrations would increase bitterness and astringency, but the magnitude of the impact on consumer acceptance was striking,” Vieitez and Dauber said. “This demonstrates that maximizing bioactive compound extraction does not necessarily result in a product that consumers will enjoy.”

After tasting the infusions, participants were informed about their antioxidant content and asked again about their purchase intentions. Learning about the antioxidant content moderately increased their willingness to buy the products, especially for the infusion with intermediate sensory intensity.

However, health-related information alone was not enough to overcome a strongly negative sensory experience.

“This suggests that successful olive leaf products must first achieve an acceptable sensory profile and then communicate their health benefits. Sensory quality remains the primary driver of consumer acceptance,” the researchers said.

The findings highlight a challenge familiar across the olive oil sector, in which some compounds associated with the health benefits and quality of extra virgin olive oil are also responsible for bitterness and pungency.

“The parallel is very clear,” Vieitez and Dauber said. “In extra virgin olive oil, phenolic compounds contribute to both health benefits and sensory attributes such as bitterness and pungency. In olive leaf infusions, we observed the same phenomenon.”

The researchers noted that a similar dynamic can be observed among olive cultivars.

“Arbequina oils are generally characterized by a milder sensory profile, with lower bitterness and pungency, which is often associated with their relatively lower phenolic content,” they said. “As a result, they are frequently preferred by consumers who are not accustomed to intense olive oils.”

By contrast, cultivars such as Coratina and Picual are known for producing olive oils with significantly higher phenolic concentrations and more pronounced bitterness and pungency.

“While these sensory attributes are often appreciated by experienced consumers and are linked to greater antioxidant potential, they can also limit acceptance among the general public,” the researchers said.

Vieitez and Dauber said olive oil and olive leaf infusions face the same fundamental challenge.

“The challenge is finding the right balance between maximizing bioactive compounds and maintaining a sensory profile that consumers are willing to accept and enjoy,” they said.

The researchers said some infusions may offer the most effective compromise between phenolic content and consumer acceptance.

“Our results suggest that such a balance does exist,” Vieitez and Dauber said. “Infusions prepared with broken leaves rather than powdered leaves provided substantial amounts of polyphenols and antioxidant activity while maintaining significantly better consumer acceptance.”

They added that visual appearance may also play an important role in consumer perceptions.

“Consumers can easily identify pieces of olive leaves, whereas a green powder may be perceived as less natural or more difficult to associate with its botanical origin,” they said. “This greater visual authenticity could represent an additional advantage for market acceptance.”

“Particle size was by far the most influential factor in our study,” Vieitez and Dauber said. “Many olive leaf infusions currently marketed in Uruguay are sold as whole leaves, which, according to our results, release relatively low amounts of polyphenols during infusion.”

At the same time, they cautioned that maximizing extraction should not become the sole objective.

“Excessive grinding can negatively affect sensory quality, so the goal should not simply be maximum extraction but rather optimization,” they said.

Beyond infusions, the researchers believe olive leaves represent a largely untapped resource for a wide range of applications.

“We believe the opportunities are extensive,” they said. “Olive leaves are an abundant and underutilized source of phenolic compounds with demonstrated antioxidant, anti-inflammatory, antimicrobial and antihypertensive properties.”

Potential applications include functional foods, dietary supplements, natural antioxidants for food preservation, cosmetics and pharmaceutical products.

“In our view, olive leaves should no longer be regarded as waste but rather as a valuable raw material within a circular bioeconomy framework,” the researchers said.

They added that olive leaf valorization extends beyond extraction yields and laboratory measurements, encompassing consumer acceptance, sustainability and commercial viability.

“The best solution is not necessarily the extract with the highest phenolic content, but the one that creates the greatest overall value within the food system,” the researchers concluded.