Almond hull biomass: Preliminary characterization and development of two alternative valorization routes by applying innovative and sustainable technologies

Abstract

Almonds are considered one of the most valuable fruits worldwide due to its high nutritional value. Moreover, a growing attention has been paid over the last years to other parts of the fruit, such as skins, shells or hulls, which are commonly found as almond by-products and scarcely exploited for valorization. In this study, two approaches were evaluated. Firstly, a green innovative processing technology, pulsed electric fields (PEF), was applied for the first time to assist the extraction of antioxidant compounds from almond hull biomass (AH). In particular, this technology was used with the aim of developing a feasible valorization strategy, being a sustainable alternative for polyphenols extraction compared to traditional methods. Then, the total phenolic content (TPC) and the antioxidant activity (TEAC and ORAC values) were measured, obtaining a higher extraction of TPC and TEAC values when PEF was used compared to conventional soaking. Secondly, the characterization of AH by means of fiber, ultimate and proximate analysis was carried out. Ultimate and proximate analysis provided information about the exploitation towards bioenergy and biofuels, demonstrating the so-called derived AH-EFB being useful for that purpose. Moreover, the high percentage in terms of carbohydrates suggests that AH could be a useful source for high-added-value chemicals, such as levulinic acid, furfural and 5-hidroximethylfurfural, displaying an interesting energetic valorization route for this biomass.