High-Pressure-Assisted Extraction of Phenolic Compounds from Olive Leaves: optimization and Comparison with Conventional Extraction

Abstract

The scope of the study was to optimize high-pressure-assisted extraction (HPAE) conditions for the extraction of phenolic compounds from olive leaves and to compare the optimum HPAE conditions with conventional extraction (CE) (at 50 °C for 30 min). In this regard, different treatment pressure levels (300−500 MPa), time (5−15 min), and solid-to-solvent ratios (0.1− 0.3 w/v) were used to optimize the total phenolic content (TPC) and oleuropein content by using the Box−Behnken design. According to the results, optimal HPAE conditions were selected as 433.3 MPa for 15 min with 0.1 w/v solid−solvent ratio to obtain the maximum TPC (57.5 mg GAE/g DW) and oleuropein content (18.45 mg/g DW). Compared to CE, HPAE increased the TPC, antioxidant capacity, and oleuropein content significantly (p ≤ 0.05). Fourier transform infrared spectroscopy results showed no difference between HPAE and CE samples. Based on scanning electron microscopy results, HPAE caused structural changes compared to CE, and this caused to increase the mass transfer rate of phenolic substances.

Guide for Optimization of Olive Leaf Extraction and Silver Nanoparticles Biosynthesis as an Initial Step for Pilot Plant Design

“…Another aspect that draws attention in the literature on olive leaf extraction is the use of technologically advanced extraction methodologies, especially including alternative energy sources: microwaves, ,, ultrasound, ,− or methods requiring the introduction of high pressure (PLE) . These methods, despite shortening the extraction time, require the use of specific equipment that increases the cost of the process and energy consumption, which again puts our proposed extraction system in a favorable perspective.…”

“…This differs from previous experiments, where researchers based work on the use of organic solvents, mainly 70−80% ethanol but also methanol or their mixtures with water. [11][12][13][14]16,20,[24][25][26][27]29,31,33 Water is an eco-friendly, safe, and green solvent, especially for food applications.…”

“…Meanwhile, Oliveira et al used the central composite design (CCD) to optimize olive leaf extraction . To improve the extraction effectiveness, plant leaves submerged in solvent are subjected to ultrasonic, − microwave, ,− or high-pressure exposure . The reducing properties of major polyphenols in the extract were used to synthesize NPs. , The simplest method for synthesizing AgNPs involves directly combining a plant extract with a silver nitrate solution.…”

Valorization of Olive Leaves through Polyphenol Recovery Using Innovative Pretreatments and Extraction Techniques: An Updated Review

“…Moreover, an optimization of high-pressure-assisted extraction conditions was carried out [94]. The results show that this optimization significantly increased the total phenolic content, antioxidant capacity, and oleuropein content compared to conventional extraction, likely due to structural changes that improved mass transfer rates.…”