Phenolic Compounds Extraction of Arbutus unedo L.: Process Intensification by Microwave Pretreatment

Agostinho M R C Alexandre,Rafael Mato,Maria Jose Cocero,Ana A Matias,Maria Rosário Bronze

doi:10.3390/pr8030298

Abstract

Arbutus unedo L., commonly known as the strawberry-tree fruit, is an endemic species of the Mediterranean flora. Microwave extraction technology has been considered as a fast and “green” method for the production of extracts rich in bioactive compounds, although the energy consumption is high. To overcome this bottleneck, microwave was used as a pretreatment procedure in short time periods. This technique promotes the burst of intracellular vacuoles leading to an increase in the lixiviation of phenolic compounds. Different approaches were tested, namely a solvent-free irradiation (SFI), a solvent-assisted irradiation (SAI) and a pressurized solvent-assisted irradiation (PSAI). After irradiation, a solid–liquid extraction procedure was performed using a mixture of water and ethanol. A kinetic evaluation of the total phenolic content (TPC) was performed using the Folin–Ciocalteu method. For the total anthocyanin content, a UV-spectrophotometric method was used. HPLC-UV and LC-MS were used for TPC and identification of present compounds. Microwave irradiation led to an increase in TPC of extracts after SAI (52%) and PSAI (66%) along with a reduction in time of extraction from 30 min to less than 2 min. The anthocyanin content also increased by 66% for the SAI and PSAI extractions.

Highlights

The Mediterranean berry Arbutus unedo, known as strawberry-tree fruit [1,2], is produced in different zones of Portugal
In order to enhance the yield of phenolic compounds, an extracting solution consisting in a water:ethanol 50:50 (v/v) mixture and a solid–liquid ratio of 1:20 were the conditions used in the present work to prepare extracts of strawberry-tree fruit
Each pretreatment consisted of different irradiation times, namely, for solvent-free irradiation (SFI) it was around 25 s, 40 s for solvent-assisted irradiation (SAI) and around

Summary

Introduction

The Mediterranean berry Arbutus unedo, known as strawberry-tree fruit [1,2], is produced in different zones of Portugal. A. unedo fruits are spherical berries with a rough surface that vary in color from yellow to red when fully ripe. Due to their perishable character, the fresh fruits are difficult to commercialize and are mostly used to prepare jams and marmalades or a characteristic distillate beverage [3,4,5,6]. The strawberry-tree fruit not adequate for fresh consumption, or the residues obtained from the distillation process used in the preparation of the traditional beverage, can be used as a source of bioactive molecules [11,12], namely phenolic compounds.

Methods

Results

Conclusion