{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,1]],"date-time":"2026-04-01T23:01:06Z","timestamp":1775084466042,"version":"3.50.1"},"reference-count":96,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2024,11,29]],"date-time":"2024-11-29T00:00:00Z","timestamp":1732838400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"National Funds by FCT\u2014Portuguese Foundation for Science and Technology","award":["UIDB\/04033\/2020"],"award-info":[{"award-number":["UIDB\/04033\/2020"]}]},{"name":"National Funds by FCT\u2014Portuguese Foundation for Science and Technology","award":["UIDB\/00772\/2020"],"award-info":[{"award-number":["UIDB\/00772\/2020"]}]},{"name":"National Funds by FCT\u2014Portuguese Foundation for Science and Technology","award":["UIDB\/00690\/2020"],"award-info":[{"award-number":["UIDB\/00690\/2020"]}]},{"name":"National Funds by FCT\u2014Portuguese Foundation for Science and Technology","award":["UIDP\/00690\/2020"],"award-info":[{"award-number":["UIDP\/00690\/2020"]}]},{"name":"National Funds by FCT\u2014Portuguese Foundation for Science and Technology","award":["LA\/P\/0007\/2020"],"award-info":[{"award-number":["LA\/P\/0007\/2020"]}]},{"name":"ortuguese Foundation for Science and Technology (FCT)","award":["UIDB\/04033\/2020"],"award-info":[{"award-number":["UIDB\/04033\/2020"]}]},{"name":"ortuguese Foundation for Science and Technology (FCT)","award":["UIDB\/00772\/2020"],"award-info":[{"award-number":["UIDB\/00772\/2020"]}]},{"name":"ortuguese Foundation for Science and Technology (FCT)","award":["UIDB\/00690\/2020"],"award-info":[{"award-number":["UIDB\/00690\/2020"]}]},{"name":"ortuguese Foundation for Science and Technology (FCT)","award":["UIDP\/00690\/2020"],"award-info":[{"award-number":["UIDP\/00690\/2020"]}]},{"name":"ortuguese Foundation for Science and Technology (FCT)","award":["LA\/P\/0007\/2020"],"award-info":[{"award-number":["LA\/P\/0007\/2020"]}]},{"name":"FCT\/MCTES (PIDDAC) to CIMO","award":["UIDB\/04033\/2020"],"award-info":[{"award-number":["UIDB\/04033\/2020"]}]},{"name":"FCT\/MCTES (PIDDAC) to CIMO","award":["UIDB\/00772\/2020"],"award-info":[{"award-number":["UIDB\/00772\/2020"]}]},{"name":"FCT\/MCTES (PIDDAC) to CIMO","award":["UIDB\/00690\/2020"],"award-info":[{"award-number":["UIDB\/00690\/2020"]}]},{"name":"FCT\/MCTES (PIDDAC) to CIMO","award":["UIDP\/00690\/2020"],"award-info":[{"award-number":["UIDP\/00690\/2020"]}]},{"name":"FCT\/MCTES (PIDDAC) to CIMO","award":["LA\/P\/0007\/2020"],"award-info":[{"award-number":["LA\/P\/0007\/2020"]}]},{"name":"SusTEC","award":["UIDB\/04033\/2020"],"award-info":[{"award-number":["UIDB\/04033\/2020"]}]},{"name":"SusTEC","award":["UIDB\/00772\/2020"],"award-info":[{"award-number":["UIDB\/00772\/2020"]}]},{"name":"SusTEC","award":["UIDB\/00690\/2020"],"award-info":[{"award-number":["UIDB\/00690\/2020"]}]},{"name":"SusTEC","award":["UIDP\/00690\/2020"],"award-info":[{"award-number":["UIDP\/00690\/2020"]}]},{"name":"SusTEC","award":["LA\/P\/0007\/2020"],"award-info":[{"award-number":["LA\/P\/0007\/2020"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Antioxidants"],"abstract":"<jats:p>The olive oil industry generates large volumes of by-products, creating notable environmental and economic concerns. Among these, olive cake (OC)\u2014a primary by-product of olive oil extraction\u2014stands out due to its high content of bioactive compounds and potential for value-added recycling. This study focused on characterizing six OC samples from the Tr\u00e1s-os-Montes and Alto Douro regions, collected at different processing times and mills. The samples included two derived from pressing (COC), two from two-phase centrifugation (TPOC; one partially pitted and one dehydrated), and two exhausted OC (EOC) samples. Fundamental analyses assessed total phenols, ortho-diphenols, flavonoids, antioxidant capacity, and tannin content. Results revealed significant variation (p &lt; 0.05) in phenolic composition, namely ortho-diphenols and flavonoid levels among the samples. EOC 2 exhibited the highest concentrations (19.61, 21.82, and 20.12 mg CAT\/g, respectively), while COC 2 had the lowest (5.08, 5.08, and 2.76 mg GA\/g, respectively). This correlated with elevated antioxidant activity in EOC 2, as measured by FRAP, DPPH, and ABTS assays (129.98, 78.00, and 56.65 \u03bcmol Trolox\/g). In contrast, COC 1 and COC 2 displayed the lowest antioxidant activities (32.61 \u03bcmol Trolox\/g in FRAP and 17.24 and 18.98 \u03bcmol Trolox\/g in DPPH). Tannin analysis showed the highest total tannin content in the dehydrated and pitted OC samples (250.31 and 240.89 mg CAT\/100 g), with COC 2 showing the lowest (88.17 mg CAT\/100 g). Condensed tannin content varied significantly, with EOC 2 presenting the highest level (328.17 mg CAT\/100 g) and COC 2 the lowest one (20.56 mg CAT\/100 g). Through HPLC-PDA-MS, 22 compounds were identified, with luteolin and verbascoside being particularly prevalent. This in-depth characterization supports the potential valorization of olive by-products, advancing sustainability and promoting a circular economy in the olive oil sector.<\/jats:p>","DOI":"10.3390\/antiox13121470","type":"journal-article","created":{"date-parts":[[2024,11,29]],"date-time":"2024-11-29T05:02:22Z","timestamp":1732856542000},"page":"1470","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":19,"title":["Exploring the Variability in Phenolic Compounds and Antioxidant Capacity in Olive Oil By-Products: A Path to Sustainable Valorization"],"prefix":"10.3390","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0009-0003-5670-3231","authenticated-orcid":false,"given":"Jessica","family":"Pai\u00e9-Ribeiro","sequence":"first","affiliation":[{"name":"Animal Science Department, University of Tr\u00e1s-os-Montes e Alto Douro (UTAD), 5000-801 Vila Real, Portugal"},{"name":"Veterinary and Animal Research Centre (CECAV), University of Tr\u00e1s-os-Montes e Alto Douro, 5000-801 Vila Real, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0009-0007-4448-2696","authenticated-orcid":false,"given":"Filipa","family":"Baptista","sequence":"additional","affiliation":[{"name":"Centre for the Research and Technology of Agro-Environmental and Biological Sciences, CITAB, University de Tr\u00e1s-os-Montes e Alto Douro (UTAD), 5000-801 Vila Real, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0300-2346","authenticated-orcid":false,"given":"Maria Jos\u00e9","family":"Gomes","sequence":"additional","affiliation":[{"name":"Animal Science Department, University of Tr\u00e1s-os-Montes e Alto Douro (UTAD), 5000-801 Vila Real, Portugal"},{"name":"Veterinary and Animal Research Centre (CECAV), University of Tr\u00e1s-os-Montes e Alto Douro, 5000-801 Vila Real, Portugal"},{"name":"AL4animals, Quinta de Prados, 5000-801 Vila Real, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4607-4796","authenticated-orcid":false,"given":"Alfredo","family":"Teixeira","sequence":"additional","affiliation":[{"name":"Mountain Research Center (CIMO), Polytechnic Instituto of Bragan\u00e7a, Campus de Santa Apol\u00f3nia, 5300-253 Bragan\u00e7a, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3052-6989","authenticated-orcid":false,"given":"Victor","family":"Pinheiro","sequence":"additional","affiliation":[{"name":"Animal Science Department, University of Tr\u00e1s-os-Montes e Alto Douro (UTAD), 5000-801 Vila Real, Portugal"},{"name":"Veterinary and Animal Research Centre (CECAV), University of Tr\u00e1s-os-Montes e Alto Douro, 5000-801 Vila Real, Portugal"},{"name":"AL4animals, Quinta de Prados, 5000-801 Vila Real, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0774-5764","authenticated-orcid":false,"given":"Divanildo","family":"Outor-Monteiro","sequence":"additional","affiliation":[{"name":"Animal Science Department, University of Tr\u00e1s-os-Montes e Alto Douro (UTAD), 5000-801 Vila Real, Portugal"},{"name":"Veterinary and Animal Research Centre (CECAV), University of Tr\u00e1s-os-Montes e Alto Douro, 5000-801 Vila Real, Portugal"},{"name":"AL4animals, Quinta de Prados, 5000-801 Vila Real, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5834-6141","authenticated-orcid":false,"given":"Ana Novo","family":"Barros","sequence":"additional","affiliation":[{"name":"Centre for the Research and Technology of Agro-Environmental and Biological Sciences, CITAB, University de Tr\u00e1s-os-Montes e Alto Douro (UTAD), 5000-801 Vila Real, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2024,11,29]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"98","DOI":"10.1016\/j.wasman.2018.04.038","article-title":"Environmental Impacts of Food Waste in Europe","volume":"77","author":"Scherhaufer","year":"2018","journal-title":"Waste Manag."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Lau, K.Q., Sabran, M.R., and Shafie, S.R. 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