Special Issue "Intensification Technologies to Efficiently Extract Antioxidants from Agro-Food Residues"

A special issue of Antioxidants (ISSN 2076-3921). This special issue belongs to the section "Extraction and Industrial Applications of Antioxidants".

Deadline for manuscript submissions: 31 December 2020.

Special Issue Editor

Dr. Soraya Rodriguez-Rojo
Website1 Website2
Guest Editor
High pressure process group, Bioeconomy Institute of University of Valladolid, Valladolid, Spain
Interests: natural products; polyphenols; essential oils; extraction; formulation; pressurized fluids; microwaves; ultrasounds

Special Issue Information

Dear Colleagues,

As is well known, there is an increasing interest in recovering phytochemicals from agricultural, forestry, and food industry residues, aiming to reduce their environmental impact and improve sustainable economic growth in the bioeconomy scheme. These phytochemicals can be employed widely in food and feed, food supplements, and cosmetics products, among others, thanks to their bioactivity properties, such as antioxidant, antimicrobial, etc.

The recovery of bioactive compounds from vegetal matrices involves several steps, where an adequate pre-treatment and extraction are of foremost importance. Conventional solid–liquid extraction is the technique of choice at industrial scale. Its main drawbacks are the high solvent consumption and long extraction times that may degrade thermolabile phytochemicals, due to the relative high temperature required to improve mass transfer. Additionally, the fact that some bioactive molecules, i.e., polyphenols, have internal cell localizations or are bounded to cell wall polysaccharides limits the extraction yield. 

Therefore, industrial sustainability of recovery of phytochemicals from agro-food wastes will benefit from the implementation of intensified processes covering the use of solvents with improved properties (pressurized and supercritical fluids, deep eutectic solvents or hydrotropes), nonconventional energies (microwave, ultrasound, pulsed electric) or high static pressure. All these technologies, which are being studied at laboratory and pilot scale, aim to develop highly efficient methods for the extraction of phytochemicals according to the “Green Engineering principles”.

As guest editor, I cordially invite you to contribute to this Special Issue by submitting original research articles and review papers according to your notable expertise in the efficient extraction of phytochemicals from agro-food wastes.

I am also pleased to report that Antioxidants has an Impact Factor of 4.520 (Journal Citation Reports®, 2019) and ranks 10th out of 135 (Q1) titles in the category ‘Food Science & Technology’, 6th out of 61 (Q1) in ‘Chemistry, Medicinal’, and 63rd out of 298 (Q1) ‘Biochemistry & Molecular Biology’.

If you have any questions, please do not hesitate to contact me. Feel free to forward this email to researchers from all around the world with expertise in this topic.

I look forward to hearing from you.

Dr. Soraya Rodriguez-Rojo
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Antioxidants is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Agro-food residue valorization
  • Phytochemicals
  • Intensified extraction
  • Green Engineering
  • Pressurized and supercritical fluids
  • (Natural) deep eutectic solvents
  • Hydrotropes
  • Microwaves
  • Ultrasounds
  • Electrical pulsed energy

Published Papers (5 papers)

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Research

Open AccessArticle
Valorisation of Exhausted Olive Pomace by an Eco-Friendly Solvent Extraction Process of Natural Antioxidants
Antioxidants 2020, 9(10), 1010; https://doi.org/10.3390/antiox9101010 - 17 Oct 2020
Abstract
Exhausted olive pomace (EOP) is the waste generated from the drying and subsequent extraction of residual oil from the olive pomace. In this work, the effect of different aqueous solvents on the recovery of antioxidant compounds from this lignocellulosic biomass was assessed. Water [...] Read more.
Exhausted olive pomace (EOP) is the waste generated from the drying and subsequent extraction of residual oil from the olive pomace. In this work, the effect of different aqueous solvents on the recovery of antioxidant compounds from this lignocellulosic biomass was assessed. Water extraction was selected as the best option for recovering bioactive compounds from EOP, and the influence of the main operational parameters involved in the extraction was evaluated by response surface methodology. Aqueous extraction of EOP under optimised conditions (10% solids, 85 ºC, and 90 min) yielded an extract with concentrations (per g EOP) of phenolic compounds and flavonoids of 44.5 mg gallic acid equivalent and 114.9 mg rutin equivalent, respectively. Hydroxytyrosol was identified as the major phenolic compound in EOP aqueous extracts. Moreover, these extracts showed high antioxidant activity, as well as moderate bactericidal action against some food-borne pathogens. In general, these results indicate the great potential of EOP as a source of bioactive compounds, with potential uses in several industrial applications. Full article
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Open AccessArticle
Enzyme Selection and Hydrolysis under Optimal Conditions Improved Phenolic Acid Solubility, and Antioxidant and Anti-Inflammatory Activities of Wheat Bran
Antioxidants 2020, 9(10), 984; https://doi.org/10.3390/antiox9100984 - 13 Oct 2020
Abstract
Valorization of wheat bran (WB) into new high-value products is of great interest within the framework of sustainability and circular economy. In the present study, we utilized a multi-step approach to extract nutraceutical compounds (phenolic acids) from WB and improved its antioxidant and [...] Read more.
Valorization of wheat bran (WB) into new high-value products is of great interest within the framework of sustainability and circular economy. In the present study, we utilized a multi-step approach to extract nutraceutical compounds (phenolic acids) from WB and improved its antioxidant and anti-inflammatory properties through using sequential hydrothermal and enzymatic hydrolysis. Thirteen commercial glycosidases differing in their specific activity were screened and compared for hydrolytic efficiency to release monosaccharides, ferulic acid, and diferulic acid. Ultraflo XL was selected as the desired enzyme treatment on the basis of its higher WB solubilization, as well as its monosaccharide and phenolic acids yields. The relationships between better hydrolytic performance of Ultraflo XL and its particular activity profile were established. To determine the optimum conditions for Ultraflo XL treatment, we tested different factors (solvent pH, incubation temperature, and time) under 15 experiments. A multicomponent analysis (MCA), including central composite design, model fitness, regression coefficients, analysis of variance, 3D response curves, and desirability, was used for processing optimization. A beneficial effect of autoclave treatment on the release of phenolic compounds was also evidenced. The results of MCA showed involvement of linear, quadratic, and interactive effects of processing factors, although solvent pH was the main determinant factor, affecting enzymatic extraction of phenolics and bioactivity of hydrolysates. As compared to control WB, under optimized conditions (47 °C, pH = 4.4, and 20.8 h), WB hydrolysates showed 4.2, 1.5, 2, and 3 times higher content of ferulic acid (FA) and capacity to scavenge oxygen radicals, chelate transition metals, and inhibit monocyte chemoattractant protein-1 secretion in macrophages, respectively. These approaches could be applied for the sustainable utilization of WB, harnessing its nutraceutical potential. Full article
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Open AccessArticle
Effect of High Hydrostatic Pressure Extraction on Biological Activities and Phenolics Composition of Winter Savory Leaf Extracts
Antioxidants 2020, 9(9), 841; https://doi.org/10.3390/antiox9090841 - 08 Sep 2020
Abstract
Satureja montana L. has several biological properties related to its diverse composition of secondary metabolites. Nevertheless, it has been mainly studied for its essential oil, with only a few studies on the profile and bioactivities of the bioactive compounds from its leaf extracts [...] Read more.
Satureja montana L. has several biological properties related to its diverse composition of secondary metabolites. Nevertheless, it has been mainly studied for its essential oil, with only a few studies on the profile and bioactivities of the bioactive compounds from its leaf extracts being reported. This work aimed to study the antioxidant activity (by oxygen radical absorbance capacity (ORAC) assay), antimicrobial minimum inhibitory and bactericidal concentrations (MIC and MBC) determination, antibiofilm (by colorimetry), impact upon DNA (anti- and pro-oxidant assay), and cytotoxicity (by cell metabolism viability assays) of S. montana extracts obtained by high-pressure-assisted extraction (HPE). The extract obtained at 348 MPa, 35% (v/v) ethanol presented the highest concentration of individual phenolic compounds, and a minimum bactericidal concentration of 20 mg/mL against Listeria monocytogenes. HPE extracts showed antioxidant activity not only in ORAC but they were also able to prevent/attenuate peroxide-induced damage upon DNA. Moreover, on its own, HPE extract induced less oxidative damage than the control extract. Concerning the cytotoxicity, HPE extracts (at 0.5 and 1.0 mg/mL) were not harmful to HT29 cell lines, while control extracts (obtained at atmospheric pressure) at higher concentrations (>1.0 mg/mL) slightly reduced the metabolism of the cells. Finally, all extracts showed inhibition of the viability of 3 cancerous cell lines (>2.0 mg/mL for Caco-2, HeLa, and TR146) to below 15%. Full article
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Open AccessArticle
Batch and Flow Ultrasound-Assisted Extraction of Grape Stalks: Process Intensification Design up to a Multi-Kilo Scale
Antioxidants 2020, 9(8), 730; https://doi.org/10.3390/antiox9080730 - 10 Aug 2020
Abstract
Nowadays, approximately 1 billion kg/y of grape stalks, with a remarkable polyphenols content, are produced worldwide. In this paper, the extraction process intensification of polyphenols in water was achieved under ultrasound-assisted recovery, focusing on kinetics and scaling-up factors. Immersion and cup-horn systems were [...] Read more.
Nowadays, approximately 1 billion kg/y of grape stalks, with a remarkable polyphenols content, are produced worldwide. In this paper, the extraction process intensification of polyphenols in water was achieved under ultrasound-assisted recovery, focusing on kinetics and scaling-up factors. Immersion and cup-horn systems were exploited as acoustic cavitation sources, and the total phenolic content (TPC) was chosen to assess the process efficiency. The kinetics were evaluated by Peleg’s hyperbolic model, and the effect of both the initial feedstock granulometry and ultrasound size-reduction were determined. The results were compared with conventional extraction methods (data analysis by ANOVA). The best polyphenols yield was obtained after 45 min of sonication, giving between 29.71 and 31.89 mg/g (gallic acid equivalents over the dry matter). The extracts were characterized using HPLC-DAD, UPLC-ESI-MS/MS, DPPH assay (2,2-diphenyl-1-picrylhydrazyl), TEAC assay (Trolox equivalent antioxidant capacity), and proanthocyanidin content determination. The flow-mode extraction procedure of grape stalks (2 kg) was carried out in a 15 L reactor. A semi-industrial decanter unit and a bag-filter were the keys units of the downstream operations. The resulting particle-free solution underwent nanofiltration on a membrane pilot skid, providing a final polyphenols-enriched stream concentrated up to 355.91%, as shown by the antioxidant activity and TPC. Full article
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Open AccessArticle
Phenylethyl Isothiocyanate Extracted from Watercress By-Products with Aqueous Micellar Systems: Development and Optimisation
Antioxidants 2020, 9(8), 698; https://doi.org/10.3390/antiox9080698 - 03 Aug 2020
Abstract
Phenylethyl isothiocyanate (PEITC) was reported as a useful antioxidant, anti-inflammatory, and chemopreventive agent. Due to technological and stability issues, it is necessary to be able to extract PEITC from its natural matrix (watercress) through sustainable and scalable methodologies. In this article, we explored, [...] Read more.
Phenylethyl isothiocyanate (PEITC) was reported as a useful antioxidant, anti-inflammatory, and chemopreventive agent. Due to technological and stability issues, it is necessary to be able to extract PEITC from its natural matrix (watercress) through sustainable and scalable methodologies. In this article, we explored, for the first time, the extractive capacity of aqueous micellar systems (AMSs) of two non-ionic surfactants. For this, we compared the AMSs with conventional organic solvents. Furthermore, we developed and optimised a new integral PEITC production and extraction process by a multifactorial experimental design. Finally, we analysed the antioxidant capacity by the oxygen radical absorbance capacity (ORAC) and ABTS methods. As results, the AMSs were able to extract PEITC at the same level as the tested conventional solvents. In addition, we optimised by response surface methodology the integrated process (2.0% m/m, 25.0 °C, pH 9.0), which was equally effective (ca. 2900 µg PEITC/g watercress), regardless of the surfactant used. The optimal extracts showed greater antioxidant capacity than pure PEITC, due to other antioxidant compounds extracted in the process. In conclusion, by the present work, we developed an innovative cost-effective and low environmental impact process for obtaining PEITC extracts from watercress by-products. Full article
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