Egyptian <i>Opuntia ficus-indica</i> (OFI) Residues: Recovery and Characterization of Fresh Mucilage from Cladodes

The utilization of biopolymers gained recent attention worldwide due to their effective role in producing eco-friendly and economical products. Mucilage from <i>Opuntia ficus-indica</i> (OFI, and other succulent plants) has the capacity to absorb huge amounts of water, forming a viscous colloid with interesting rheological properties. It also had the potential ability for use as food additives or food technological products. We, therefore, aimed at extracting and characterizing pure liquid mucilage from the cladodes of OFI (Egyptian variety) using multidimensional approaches including HPLC-RID, FTIR, XRD, NMR, DSC, and TGA assays. The chemical composition, total polyphenols, total flavonoids, total flavonols, and antioxidant capacity by DPPH and ABTS assays were also measured. HPLC-RID analysis showed that the mucilage’s sugars are composed of glucose, xylose, rhamnose, galacturonic acid, arabinose, galactose, and fucose with total sugars of 0.375 mg/mL, which were subsequently confirmed by FTIR and NMR results. The specific signals of these sugars were also observed in ¹³C and ¹H NMR spectra and their chemical fingerprint was obtained by FTIR. XRD patterns showed that mucilage has high calcium content, and the glass transition temperature was observed at 85.9 °C. Meanwhile, total phenolic content, flavonoids, and flavonols were about 7.96 mg GAE/g FW, 3.61 mg QE/g FW, and 1.47 mg QE/g FW, respectively. The antioxidant capacity of mucilage was around 26.15 and 22.5 µmol TE/g FW for DPPH and ABTS methods, respectively. It can be concluded that OFI cladode mucilage showed promising properties that would improve and open new opportunities and trends in the food, pharmaceutical, cosmetic, and other industries. The use of pure liquid mucilage could also be economically profitable due to its low cost, availability, and effectiveness for many edible applications.