Roles of Drying, Size Reduction, and Blanching in Sustainable Extraction of Phenolics from Olive Leaves

Fereshteh Safarzadeh Markhali

doi:10.3390/pr9091662

Abstract

It is now known that olive leaves contain a sizable portion of polyphenols and there is much research highlighting that these natural ingredients favorably exhibit bio-functional activities. In this regard, many studies have focused on the exploration of optimum conditions involved directly in the extraction process. These investigations, while being highly valuable, may somewhat cast a shadow over other contributing factors such as those involved in the preprocessing of leaves, including size reduction, drying, and blanching. The use of these unit operations under appropriate conditions, together with other benefits, potentially exert improved surface area, homogeneity, and diffusion/mass transfer which may help develop the liberation of target bio-compounds. The research work in this area, particularly size reduction, is relatively limited. Although in various experiments they are incorporated, not many studies have focused on them as the main predictor variables. The performance of further research may help ascertain the magnitude of their effects. Consideration of the operational parameters in preprocessing step is equally important as those in the processing/extraction step that may comparably influence on the extraction efficiency. This review provides an overview of the potential roles of drying, size reduction, and blanching in the extraction efficiency of phenolics from olive leaves.

Highlights

IntroductionOlive leaves form a large proportion of biomass residues derived from (i) agricultural practices (mainly at pruning stage) [1,2], and industrial processing of olive oil and table olives [3,4,5]
Olive leaves form a large proportion of biomass residues derived from (i) agricultural practices [1,2], and industrial processing of olive oil and table olives [3,4,5]
Given the fact that many studies tend to stress the importance of the main processing/extraction parameters, together with the potential practicalities of the abovementioned pretreatments, it may be worthwhile to highlight an overview of the effects of these unit operations and emphasize that there is a need to take them into account when addressing the challenges involved in the extraction/bioactivity of phenolic compounds from olive leaves

Summary

Introduction

Olive leaves form a large proportion of biomass residues derived from (i) agricultural practices (mainly at pruning stage) [1,2], and industrial processing of olive oil and table olives [3,4,5]. Among the key factors include the operational parameters associated with the preprocessing/pretreatment step which are comparably as important as those involved during the actual extraction. These include size reduction, drying, and blanching that are among the most common approaches applicable to olive leaves. Given the fact that many studies tend to stress the importance of the main processing/extraction parameters, together with the potential practicalities of the abovementioned pretreatments, it may be worthwhile to highlight an overview of the effects of these unit operations and emphasize that there is a need to take them into account when addressing the challenges involved in the extraction/bioactivity of phenolic compounds from olive leaves

Drying

Size Reduction

Blanching

Future Perspectives

Findings

Conclusions