{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,25]],"date-time":"2026-04-25T17:05:12Z","timestamp":1777136712923,"version":"3.51.4"},"reference-count":35,"publisher":"MDPI AG","issue":"23","license":[{"start":{"date-parts":[[2021,12,2]],"date-time":"2021-12-02T00:00:00Z","timestamp":1638403200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e Tecnologia","doi-asserted-by":"publisher","award":["UIDB\/00100\/2020"],"award-info":[{"award-number":["UIDB\/00100\/2020"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"name":"European Union\u2019s Horizon 2020, Marie Sklodow-Curie","award":["778168"],"award-info":[{"award-number":["778168"]}]},{"name":"Ministry of Education and Science of Bulgaria","award":["DH 07\/12"],"award-info":[{"award-number":["DH 07\/12"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>In this study, sustainable technology microwave-assisted extraction (MAE) in association with green solvents was applied to recover phenolic compounds from spent coffee grounds (SCGs). A design of experiments (DOE) was used for process optimization. Initially, a 24\u22121 two level Fractional Factorial Design was used and ratios \u201csolvent to solute\u201d and \u201cethanol to water\u201d were identified as the significant experimental factors. Consequently, Central Composite Design (CCD) was applied to analyze the effects of the significant variables on the response yield, total polyphenols content (TPC), and antioxidant activity (AA) by the DPPH assay method, and quadratic surfaces to optimize those responses were generated. The values of the significant factors of 16.7 (solvent\/solute) and 68.9% (ethanol\/water) were optimized simultaneously the yield (%) at 6.98 \u00b1 0.27, TPC (mg GAE\/g) at 117.7 \u00b1 6.1, and AA (\u00b5mol TE\/g) at 143.8 \u00b1 8.6 and were in excellent agreement with those predicted from the CCD model. The variations of the compositions of the lipids, caffeine, pentacyclic diterpenes, and FAME as a function of the dominant factor % ethanol in the solvent mixture were analyzed by applying NMR and GC-FID, and the results obtained confirmed their determinative significance.<\/jats:p>","DOI":"10.3390\/molecules26237320","type":"journal-article","created":{"date-parts":[[2021,12,2]],"date-time":"2021-12-02T21:19:08Z","timestamp":1638479948000},"page":"7320","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":38,"title":["Microwave-Assisted Extraction of Phenolic Compounds from Spent Coffee Grounds. Process Optimization Applying Design of Experiments"],"prefix":"10.3390","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8118-0864","authenticated-orcid":false,"given":"Jos\u00e9","family":"Coelho","sequence":"first","affiliation":[{"name":"Instituto Superior de Engenharia de Lisboa, Instituto Polit\u00e9cnico de Lisboa, Rua Conselheiro Em\u00eddio Navarro 1, 1959-007 Lisboa, Portugal"},{"name":"Centro de Qu\u00edmica Estrutural, Instituto Superior T\u00e9cnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8200-6910","authenticated-orcid":false,"given":"Maria","family":"Robalo","sequence":"additional","affiliation":[{"name":"Instituto Superior de Engenharia de Lisboa, Instituto Polit\u00e9cnico de Lisboa, Rua Conselheiro Em\u00eddio Navarro 1, 1959-007 Lisboa, Portugal"},{"name":"Centro de Qu\u00edmica Estrutural, Instituto Superior T\u00e9cnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal"}]},{"given":"Stanislava","family":"Boyadzhieva","sequence":"additional","affiliation":[{"name":"Institute of Chemical Engineering, Bulgarian Academy of Sciences, Academic Georgi Bontchev str., 1113 Sofia, Bulgaria"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4834-8183","authenticated-orcid":false,"given":"Roumiana","family":"Stateva","sequence":"additional","affiliation":[{"name":"Institute of Chemical Engineering, Bulgarian Academy of Sciences, Academic Georgi Bontchev str., 1113 Sofia, Bulgaria"}]}],"member":"1968","published-online":{"date-parts":[[2021,12,2]]},"reference":[{"key":"ref_1","unstructured":"(2021, June 07). The International Coffee Organization. Available online: https:\/\/www.ico.org\/."},{"key":"ref_2","first-page":"640","article-title":"Green extraction of high added value substances from spent coffee grounds: Preliminary results","volume":"53","author":"Georgieva","year":"2018","journal-title":"J. Chem. Technol. 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