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Browsing by Author "Guizani, Khaoula"

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  • Olive by-products characterization and optimization of extraction techniques to recover bioactive compounds
    Publication . Guizani, Khaoula; Melgar Castañeda, Bruno; Rodrigues, Ana Isabel G.
    In the rapidly growing world, there’s a substantial demand for food. The current challenge extends beyond the need for more food; it involves a concerning surge in food waste, posing interconnected risks to the environment, health, and the economy. Numerous studies have been addressing this issue and minimizing environmental harm. Plant waste, generated during cultivation, processing, and consumption, contains a wealth of bioactive compounds with various beneficial effects, for example antioxidant activities. The Olea europaea leaves were extracted using dynamic maceration extraction (DE) for 1 h and 3 h, ultrasound-assisted extraction (UAE), and microwave-assisted extraction (MAE) to evaluate the antioxidant potential of the resultant extracts. Four antioxidant assays were performed, including 2,2-Diphenyl 1-picrylhydrazyl (DPPH), 2,2’-azinobis-(3- ethylbenzothiazoline-6-sulfonic acid) (ABTS), Ferric ion reducing antioxidant power (FRAP), and reducing power (RP). The total phenolic compounds (TPC) content was also determined. The results showed that DE-3h presents the highest TPC value compared to DE-1h, UAE and MAE which showed approximately similar amounts. DPPH, FRAP, and RP showed better results than ABTS test. Considering cost-effectiveness, DE comes up as the preferred extraction technique over UAE and MAE, particularly for evaluating various responses, with a specific emphasis on the DPPH test due to its specificity and simplicity compared to the other tests. DE extraction was performed using two solvents: methanol and acetone through a central composite design (CCD) to study the effect of three factors numerical (time of extraction, percentage of solvent, and pH level) and 1 categorical factor (Solvent type) on five responses (DPPH, TPC, yield of extraction, carotenoids, and chlorophylls determination). An exploratory data analysis (EDA) complemented this assessment. Carotenoids and chlorophylls demonstrated higher extractability when utilizing acetone, while the DPPH assay and extraction yields exhibited better results when methanol was used for extraction. In terms of fitting models, response surface methodology (RSM) was applied for all independent and dependent variables, allowing us to suggested optimization with a desirability value of 65.6% including the following parameter values: Extraction time (A) = 120 minutes, Solvent percentage (B) = 78%, Solvent pH (C) = 5, and Solvent type = Acetone. Which yields 2.51 μg/mL of TCC, 6.05 μg/mL of Chlorophyll A content, 18.4 μg Trolox equivalent/mL o for the DPPH test, 108.72 μg gallic acid equivalent/mL for the TPC test, and an extraction yield of 50.7%.
    2024Master thesis Open access Show more