431: Process Optimization of Subcritical Water Extraction of Phenolic and Antioxidant Constituents From California Olive Pomace

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Location: McCormick Place, South Hall Booth S0170

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2-Sentence Summary:

Phenolic compounds with health benefits can be extracted from valuable olive pomace (OP) for upcycling and valorization of agricultural byproducts from the olive oil industry. The study optimized parameters for the phenolic extraction using subcritical water extraction, which is a novel and nontoxic technology.



Phenolic compounds with health benefits can be extracted from valuable olive b olive pomace (OP). High-temperature and high-pressure conditions, subcritical water extraction (SWE), is an emerging nontoxic processing method that reduces water polarity enabling subcritical water to behave similarly to less polar solvents such as methanol or ethanol. While SWE has been used for phenolic extraction from European olive pomace (OP), limited knowledge is available for US California OP and the optimized operation parameters.



California OP was extracted by SWE within an experimental design of response surface regression (RSR) by 3-factors by 3-levels. The temperature was set at 80, 140, and 200°C; the static time was 5, 10, and 15 mins; and the running cycle was 1, 2, and 3, respectively. Extracts were evaluated using pH, total phenolic content (TPC) by Folin-Ciocalteu assay in gallic acid equivalent (GAE), individual phenolics by high-performance-liquid-chromatography (HPLC), and antioxidant activities by 2,2′-diphenyl-1-picrylhydrazyl radical (DPPH) assay in Trolox equivalent (TrE).


The pH dropped from 4.8- 5.1 at 80 and 140°C to 4.2-4.4 at 200°C. p-values of temperature, running cycle, and static time were 0.028, 0.206, and 0.174 for the RSR model constructed for TPC; and were 0.003, 0.681, and 0.180 for DPPH. Higher phenolics were extracted by increasing the temperature; three cycles were better than 1 or 2 cycles; while the static time was less influential for phenolic extraction. The higher the temperature facilitated antioxidant capacity of extract; the antioxidant capacity increased as static time increased; however, cycles were not influential for antioxidant capacity. The highest extract rate was 85.572 mg GAE/g OP dry weight and 576.661 µmol TrE/g OP dry weight at 200°C, 10 minutes static time, and 3 cycles. The optimum condition estimated by RSR for phenolics extraction and higher antioxidant capacity is around 200°C, 15 minutes static time, and 3 cycles.

Scientific evidence that supports the valorization and upcycles of  US California OP has been presented by the study using novel and nontoxic SWE technology. The study also provides substantial data foundations for the further practical applications of the utilization of OP extracts as natural food preservatives and antimicrobial agents.

Author(s): Hefei Zhao, Roberto J. Avena-Bustillos, and Selina C. Wang