The avocado peel as a source of catechins: A comparison between extraction technologies and the influence of fruit variety

Abstract

The bioactive components in agro-industrial wastes can be extracted to obtain compounds of industrial interest. The present study is focused on analyzing the composition of avocado peel extracts obtained by solvent extraction, ultrasound, and supercritical fluids by two varieties of avocado. As a result, differences in the composition of avocado peels and the yields presented in the extraction processes are evidenced. The solvent in the extractions strongly affected the active constituents' content and their antioxidant activities. The highest recovery of catechins is presented with ethanol at 50% v/v. Extraction with supercritical fluids increased the extraction yield to 17.14% w/w for the Hass variety and 14.20% w/w for the Lorena variety. However, in the case of the Lorena variety, supercritical fluids decreased the concentration of catechins. For the Lorena variety, ultrasound favored the extraction of catechins. The highest catechin concentrations corresponded to 151.96 mg of epicatechin and 60.77 mg of catechin per 100 g of Hass variety. The conditions that improved the extraction were 60 °C, 60 min, 0.2 mg/L (mg avocado peel per liter of solvent), and a frequency of 30 kHz. Avocado peel variety Lorena presented the highest concentrations of catechins under the same conditions (269.37 mg of epicatechin and 119.88 mg of catechin per 100 g of peel). The economic study showed better economic indicators for the Hass variety than the Lorena variety by the difference in extraction yields. The minimum production cost of the extract was 8.21 USD/kg using solvent extraction. From a technical point of view, this work made it possible to demonstrate the potential of avocado peels to obtain catechins, especially when ultrasound extractions are used. However, from an economic point of view, conventional techniques such as solvent extraction are recommended to extract flavonoids such as catechins.