Development of a green ultrasound-assisted procedure for the extraction of phenolic compounds from avocado peel with deep eutectic solvents

Abstract

Avocado (Persea americana Mill.) is a tropical fruit grown in different areas of the world. Avocado pulp is of interest to food companies while seed and peel are wasted. In 2021, about 25 thousand tons of avocado peel were produced as waste. In accordance with circular economy and green chemistry principles, avocado peel could be considered a source of bioactive molecules, specifically phenolic compounds, to be recovered using green methods. Deep eutectic solvents (DESs) are green solvents whose extractive efficiency for phenolic compounds from food and waste products of the agri-food chain has already been demonstrated. In this work, an ultrasound-assisted solid-liquid extraction, using DESs, was developed to recover phenolic compounds from avocado (Hass variety) peel. For this purpose, twelve DESs were tested as extraction solvents considering the provided total phenolic content. Then, in order to obtain the largest amount of phenolic compounds, the most relevant factors affecting solid-liquid extraction were evaluated. Matrix-to-solvent ratio of 1:30 (w/v), 25°C and 15 min as temperature and time of extraction, respectively, were found as optimal conditions to guarantee an extracted amount of phenolic compounds of 8.29 ± 0.07 g GAE/100g of dry avocado peel. Through high-performance liquid chromatography coupled with photodiode array and mass spectrometry detection, some flavonoids and phenolic acids were identified in the avocado peel extract.