Avocado-derived biomass: chemical composition and antioxidant potential

Avocado has become fashionable due to its great properties. It is consumed as a fresh product and it is also processed to obtain salad oil and guacamole. In all cases, the only usable portion is the pulp. Therefore, to be a more sustainable and profitable agribusiness, it is important to recognize which compounds from the peel and the stones waste can be converted into valuable bio-products. Therefore, their chemical composition was determined according to the National Renewable Energy Laboratory, the total phenolic content by the Folin-Ciocalteu method and the antioxidant properties by the FRAP and TEAC assays.

The main components of the peel and stones were acid-insoluble lignin (35.0 and 15.3%, respectively), polymeric sugars (23.6 and 43.9%, respectively), and the aqueous extractives (15.5% and 16.9%, respectively). Both biomasses contain lipids and protein, but a minor proportion (<6%). The valorization of lignin and sugars is of interest given the high content; particularly, stones are a rich source of glucose (93.2% of the polymeric fraction), which could be used to obtain biofuels or derivatives of interest. The extractive fraction of the peels contained the highest amount of phenolic compounds (4.7 g/100 g biomass), mainly, concentrated in the aqueous fraction (i.e. 87%) compared to the ethanol one, which was subsequently extracted. It correlated with a major antioxidant activity and thereby the peels can be applied to obtain antioxidants and water can be used as an environmentally friendly extraction solvent.