Abstract
Currently, interest in finding new feedstock as sources of natural food antioxidants is growing. The extracted olive pomace (EOP), which is an agro-industrial residue from the olive pomace extracting industries, is generated yearly in big amounts, mainly in the Mediterranean countries. EOP was subjected to an ultrasound assisted extraction with ethanol-water mixtures. The effect of main parameters, such as ethanol concentration (30–70% v/v), ultrasound amplitude (20–80%), and extraction time (5–15 min), on the extraction of antioxidant compounds was evaluated according to a Box–Behnken experimental design. The antioxidant capacity of the resulting extracts was determined by measuring their content in total phenolic compounds (TPC) and flavonoids (TFC), as well as their antioxidant activity by DPPH, ferric reducing antioxidant power (FRAP), and ABTS assays. Considering the simultaneous maximization of these five responses, the optimal conditions were found to be 43.2% ethanol concentration, 70% amplitude, and 15 min. The ultrasound assisted extraction of EOP under these optimized conditions yielded an extract with a phenolic and flavonoid content (per gram of EOP) of 57.5 mg gallic acid equivalent (GAE) and 126.9 mg rutin equivalent (RE), respectively. Likewise, the values for DPPH, ABTS, and FRAP assay (per gram of EOP) of 56.7, 139.1, and 64.9 mg Trolox equivalent, respectively were determined in the optimized extract.
Highlights
In recent years, the demand for natural antioxidants as alternatives to synthetic antioxidants has increased
The Box–Behnken design was applied to study the impact of the three variables on the ultrasound-assisted extraction of extracted olive pomace (EOP)
Ethanol-water mixtures were selected as the extraction solvents following results that were obtained in our laboratory with other olive residues [17]
Summary
The demand for natural antioxidants as alternatives to synthetic antioxidants has increased Phenolic compounds, such as flavonoids, phenolic acids, phenolic alcohols, stilbenes, lignans, and tannins, exhibit antioxidant activities and other types of bioactivity (anti-inflammatory, anticarcinogenic, antiviral, hepatoprotective, and neuroprotective activities, among others) [1,2]. These properties make these compounds useful in the food and pharmaceutical industries as food preservatives and biocompounds for human health [3]. The residual biomass from agro-industrial processes could be a cheap and abundant source of high-added value compounds. The valorisation of these by-products within the context of biorefineries that produce biofuels, power, and chemicals within a single installation might help in diversifying the economies of rural areas and developing an industrial complex [4].
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