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Indigenous and non-commercial fruits can be an important source of antioxidant polyphenols; however, the identity and content of polyphenols from non-commercial fruits are often poorly described. The study aimed to extract, identify, and quantify polyphenols from the skin of the indigenous Africa fruit Ximenia caffra, using solvent extraction. Three solvents (hexane, acetone, and 70% v/v ethanol) over three extraction times (30, 60 and 120 min) were used in a 32 full factorial experimental design to determine effects on polyphenol recovery, and individual polyphenolics were characterised using liquid chromatography high-resolution mass spectrometry (LC-HRMS). Ethanol was the most effective extraction solvent, and extracts had high levels of total phenolics and flavonoids (65 mg gallic and 40 mg catechin equivalents per gram dry sample respectively), and high antioxidant activity (18.2 mg mL−1 ascorbic acid equivalents). LC-HRMS positively identified 16 compounds, of which 14 were flavonoids including flavonoid glycosides, and indicated that concentrations of some flavonoids decreased for extraction times beyond 60 min. It was concluded that the fruit of Ximenia caffra is rich in natural polyphenolic antioxidants; the present work identified and quantified a number of these, while also establishing suitable solvent extraction conditions for the recovery of these potentially high-value compounds.

Eggshells are among the emerging hazardous waste from the food processing industry. This work sought to valorize waste guinea fowl eggshells. Guinea fowl eggshells (GFEs) were evaluated in the production of CaO for chemical and industrial application. The functionality, thermal stability, elemental composition, phase distribution and surface morphology properties of uncalcined GFEs and GFEs calcined at 700˚C, 800˚C, 900˚C, 1000˚C and 1100˚C were systematically studied by FTIR, TGA, XRF, XRD and SEM-EDX respectively. The elemental analysis revealed Ca as the main element in the GFEs. The uncalcined GFEs showed intense peaks that corresponded to calcite (CaCO 3) phases. These transformed into Ca(OH) 2 as the temperature of calcination increased and finally to CaO in the FTIR analysis. In the XRD diffractograms, the main peaks at 2θ values were 29.466˚ for the uncalcined GFESs and at 37.377˚ for the sample treated at 1100˚C. The phases were confirmed as CaO when compared with JCPDS files. Using the Scherer equation, the CaO crystallite size for the sample calcined at 1100˚C was found to be 50.68 nm along the (2 0 0) orientation. All the samples showed multi-step decomposition patterns in the thermogravimetric analyses (TGA), with weight loss of up to 47% for the uncalcined GFEs sample, which was mainly due to the transformation of the calcite (CaCO 3) phase to CaO by removal of bound water, organic components, and CO 2. Samples calcined at 1100˚C showed mainly CaO phases in XRD analyses and fairly stable with 7% loss in weight after treatment at 800˚C. SEM images of samples calcined at 900˚C were irregular compared to samples treated at 1100˚C. EDX data revealed that the surface structure was 100% calcium and oxygen. GFEs are a potential source of pure calcium oxide for various industrial uses.

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