Recovery of essential oils, polyphenols, fermentable sugars, and pectin from orange residues

Abstract

Residues from orange processing are being continuously generated in vast amounts due to the increasing demand for this fruit and its byproducts worldwide. The valorization of Orange Residues is challenging in contrast to conventional “lignocellulosic residues” since this fruit-derived biomass contains high amounts of pectin and an extractive fraction rich in sugars, essential oils, and polyphenols. The relative amounts of these fractions are highly influenced by the juice/pulp extraction process. Even though several studies have explored how to produce added value from this biomass, it is necessary to compare how different techniques and operating conditions influence the bioactive compounds that can be recovered and the remnant biomass after processing. This study compares essential oil extraction, solvent extraction, and acid hydrolysis for fermentable sugar and pectin production to elucidate a feasible sequence for a biorefinery from Orange Residues. From our results, it was proposed a technically feasible sequence that maximizes the yields of i) essential oils (0.70 ± 0.05 g/ 100 g DM) from steam distillation (4 h, 1500 W), ii) naringin (0.19 g/100 g DM), hesperidin (1.27 g/100 g DM), and glucose (3.9 g/100 g DM) from solid-liquid extraction (Ethanol 61.6 % (w/v), 45.8 °C, 155.5 min, and 5 % (w/v) biomass load), iii) pectin (25.24 g/100 g DM) from citric acid hydrolysis (pH 1.5, 90 °C, 82.1 min, and 5 % (w/v) biomass load), and iv) glucose (12.41 g/100 g DM) and xylose (10.13 g/100 g DM) from sulfuric acid hydrolysis (Sulfuric acid 0.68 % (w/v), 121 °C, 24.1 min, and 7.32 % (w/v) biomass load), in a biorefinery scheme.