Maximum valorization of red prickly pear peels through green extraction techniques of bioactive compounds and cellulose microfibers.

This study evaluated the effect of particle size (375-116 μm) on the chemical composition of red prickly pear (Opuntia ficus-indica) peels, as well as on the ultrasound-assisted extraction of bioactive compounds using an ethanol:water (40,60 v/v) solvent at 30 °C. Residual biomass was used to obtain cellulose fiber (CF) suspensions via alkali hydrogen peroxide pretreatment and mechanical homogenization. Smallest particle (< 188 μm) significantly enhanced antioxidant activity (6.5 mg of gallic acid equivalents/g dw, IC50, 0.7 mg/mL). X-ray diffraction confirmed reduced crystallinity of CF, with the highest crystallinity index (61 %) in particles 116 μm. Infrared spectroscopy identified the presence of phenolic, carboxylic acid, and betalain compounds in the extract and confirmed the removal of non-cellulosic components. Morphology analysis showed network of CF with diameters around 180 nm for the smallest particles. Thermal analysis indicated that the thermal decomposition of CF occurs at 350 °C, higher than raw peel (300 °C), confirming improved thermal stability.