Chemical valorization of agricultural by-products: Isolation and characterization of xylan-based antioxidants from almond shell biomass

Abstract

The isolation of non-cellulosic polysaccharides from almond shells (AS) and their solid residue (ASR) after autohydrolysis was investigated using a two-step alkaline extraction without and in combination with short ultrasonic treatment. The obtained polysaccharide preparations were characterized by yield, chemical composition, and structural features, and the antioxidant activity of the water-soluble preparations tested. The results showed that the use of ultrasound at a reduced extraction time of 10 min as compared to 60 min of the classical procedure, with a 5% NaOH solution, resulted in the greatest yield of hemicelluloses. The AOA of their water-soluble portion ranged between 48 and 80%, indicating the antioxidant potential of these materials. The xylan polymers isolated from both AS and ASR might serve as biopolymer sources in native form or after targeted modification for production of value-added substances and polysaccharide-based antioxidants applicable in food, cosmetics, and other areas.