Olive Leaf Processing for Infusion Purposes

Eva María Ramírez, Manuel Brenes, Concepción Romero, Eduardo Medina, Eva María Ramírez, Manuel Brenes, Concepción Romero, Eduardo Medina

Abstract

Olive leaf is a by-product rich in bioactive compounds, such as polyphenols and triterpenic acids, with numerous biological activities for human health. Nowadays, the existence of dry olive leaves marketed for infusion elaboration is lacking. During the elaboration process, the drying and grinding stages are critical for the conservation of bioactive compounds, and, precisely, the existing research on olive leaf production procedures is quite scarce. This work aimed to study and model the dehydration process using a forced-air oven and infrared with air convection systems. In addition, different grinding grades were studied. The kinetic constant and activation energy during dehydration were obtained. Drying temperatures above 50 °C produced a decrease in the phenolic concentration of olive leaves; however, it has been observed that prior storage of 24 h at room temperature considerably reduced the loss of phenols. Likewise, it was observed that the higher the degree of grinding, the greater the diffusion of both bioactive compounds and colored compounds. Therefore, the drying and grinding stages were closely related to the content of beneficial compounds and the appearance of the infusions, and their optimization was of crucial importance to produce dried olive leaves rich in biocompounds for use as healthy infusions.

Keywords: dehydration; grinding; oleuropein; olive tea; phenolic compounds; triterpenic acids.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Relationship between the percentage of moisture (%) and drying time (h) at different temperatures. Panel (A): drying in the oven. Panel (B): drying in the infrared equipment.
Figure 2
Figure 2
Arrhenius-type relationships between the drying constant rate and temperature obtained during the dehydration of olive leaves using the oven or infrared heating.
Figure 3
Figure 3
Polyphenol concentration (mg/kg dried olive leaf) after different heat treatments. Leaves were directly dried after harvesting or after a storage period of 24 h at ambient temperature. All the heat treatments were performed until the weight was constant. Data are expressed as the mean value of triplicate. Bars mean the standard deviation. BD means before dehydration. Vertical bars with different lowercase letters indicate significant differences according to Duncan’s multiple range test (p < 0.05).

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