Assessment of the Functional Quality of Extra Virgin Olive Oil: Green Extraction of Phenolic Compounds Using Ethyl Lactate

TL;DR

This study compares ethyl lactate to methanol for extracting healthful phenolic compounds from extra virgin olive oil, finding ethyl lactate to be a green and effective alternative.

Contribution

The paper introduces ethyl lactate as a green solvent for phenolic extraction from olive oil, validated through analytical and industrial assessments.

Findings

Ethyl lactate extracted higher total phenolic content than methanol in most cases.

Phenolic extraction efficiency increased with lower water content in solvent mixtures.

Ethyl lactate and methanol produced similar HPLC profiles after acid hydrolysis.

Abstract

Phenolic compounds are regarded as one of the components responsible for olive oil’s functional properties and health benefits. These chemicals act as antioxidants and anti-inflammatories, and prevent chronic diseases. The Folin–Ciocalteu reagent or HPLC procedures are commonly used to determine the concentration of total phenolic compounds in olive oil. The use of ethyl lactate or lactic acid ethyl ester (LAEE) instead of methanol (MeOH) was examined in terms of green chemistry. Six extra virgin olive oils (EVOOs) with phenolic content ranging from 20 to 350 mg/L, were first extracted with 1:4, 2:3, 3:2, 4:1, and 5:0 MeOH or LAEE/water, (v/v), to determine total phenolic content (TPC) and antiradical activity (%RSA) using the Folin–Ciocalteu reagent and DPPH assay, respectively. The concentration of extracted phenolics or extracts’ RSA increased as the water content in the organic solvent mixture decreased. Also, TPC values were greater when extracted with LAEE than MeOH, while the differences were modest. The HPLC profiles of EVOO phenolic extracts produced by 4:1 MeOH or LAEE/water, (v/v), were indistinguishable in principal component analysis. Simplification of the phenolic profile via acid hydrolysis, resulting in increased hydroxytyrosol and tyrosol content liberated from the corresponding bound forms, showed that both organic solvents equally recovered the predominating phenols of the polar fraction. A noted limitation of LAEE extraction is the need for freeze-drying to remove it prior to HPLC analysis of aqueous extracts. Nonetheless, these findings support LAEE as an effective and environmentally friendly alternative to MeOH for EVOO phenolic extraction in both analytical and industrial contexts.

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