{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,11]],"date-time":"2026-02-11T10:28:52Z","timestamp":1770805732420,"version":"3.50.0"},"reference-count":47,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2026,2,9]],"date-time":"2026-02-09T00:00:00Z","timestamp":1770595200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Foundation for Science and Technology","award":["CIMO UID\/00690\/2025"],"award-info":[{"award-number":["CIMO UID\/00690\/2025"]}]},{"name":"Foundation for Science and Technology","award":["UID\/PRR\/00690\/2025"],"award-info":[{"award-number":["UID\/PRR\/00690\/2025"]}]},{"name":"Foundation for Science and Technology","award":["SusTEC LA\/P\/0007\/2020"],"award-info":[{"award-number":["SusTEC LA\/P\/0007\/2020"]}]},{"name":"institutional scientific employment program contract of A. Santamaria-Echart"},{"name":"FCT for the PhD research grant","award":["SFRH\/BD\/148281\/2019"],"award-info":[{"award-number":["SFRH\/BD\/148281\/2019"]}]},{"name":"Ibero-American Programme for Science and Technology for Development","award":["124RT0164"],"award-info":[{"award-number":["124RT0164"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>Interest in alternative protein sources has grown, with Spirulina, a microalga belonging to the genus Limnospira (formerly Arthrospira), emerging as a key option. Guided by sustainability principles, this study explored the gelling capacity and hydrogel-forming properties of integral Spirulina biomass (SpB), targeting applications in structured foods. Two experimental designs (DoE) were employed. One to identify key factors influencing hydrogel formation, and another to optimize the formulation (22 wt%, pH 5.6, thermal gelation at 90 \u00b0C). Syneresis analysis revealed that high SpB hydrogels experienced less water loss, with the 22% sample losing just 2.51% after 14 days, due to its dense, particulate morphology as observed by means of scanning electron microscopy. Rheological analysis confirmed the optimized formulation\u2019s superior mechanical properties, with a storage modulus (G\u2032) 24-times higher than the low concentration reference sample (~1890 Pa), remaining dominant over the loss modulus (G\u2033) (G\u2032 &gt; G\u2033) across the analysed frequency range, corroborating a strong elastic behaviour. Although the recovery tests showed partial recovery (27.1%) after high shear, the high residual stiffness (\u2248515 Pa) confirmed the material\u2019s ability to maintain its shape. These results enabled successful 3D printing tests with the optimized hydrogel, pointing out its potential for innovative food applications in structured food design.<\/jats:p>","DOI":"10.3390\/molecules31040591","type":"journal-article","created":{"date-parts":[[2026,2,9]],"date-time":"2026-02-09T12:42:42Z","timestamp":1770640962000},"page":"591","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Zero-Waste Hydrogel Design via Integral Biomass Valorization of Protein-Rich Spirulina Microalgae"],"prefix":"10.3390","volume":"31","author":[{"given":"Leandro L.","family":"Aquino","sequence":"first","affiliation":[{"name":"CIMO, LA SusTEC, Instituto Polit\u00e9cnico de Bragan\u00e7a, Campus de Santa Apol\u00f3nia, 5300-253 Bragan\u00e7a, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8057-6864","authenticated-orcid":false,"given":"Samara C.","family":"Silva-Pituco","sequence":"additional","affiliation":[{"name":"CIMO, LA SusTEC, Instituto Polit\u00e9cnico de Bragan\u00e7a, Campus de Santa Apol\u00f3nia, 5300-253 Bragan\u00e7a, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5407-4270","authenticated-orcid":false,"given":"Alejandro","family":"Hernandez-Sosa","sequence":"additional","affiliation":[{"name":"Instituto de Ciencia y Tecnolog\u00eda de Pol\u00edmeros (ICTP), CSIC, c\/Juan de la Cierva, 3, 28006 Madrid, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2503-9705","authenticated-orcid":false,"given":"Elsa C.","family":"Ramalhosa","sequence":"additional","affiliation":[{"name":"CIMO, LA SusTEC, Instituto Polit\u00e9cnico de Bragan\u00e7a, Campus de Santa Apol\u00f3nia, 5300-253 Bragan\u00e7a, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7332-0134","authenticated-orcid":false,"given":"Rebeca","family":"Hernandez","sequence":"additional","affiliation":[{"name":"Instituto de Ciencia y Tecnolog\u00eda de Pol\u00edmeros (ICTP), CSIC, c\/Juan de la Cierva, 3, 28006 Madrid, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1245-4064","authenticated-orcid":false,"given":"Eliane","family":"Colla","sequence":"additional","affiliation":[{"name":"Programa de P\u00f3s-gradua\u00e7\u00e3o em Tecnologia de Alimentos (PPGTA), Departamento Acad\u00eamico de Alimentos (DAALM), Universidade Tecnol\u00f3gica Federal do Paran\u00e1, C\u00e2mpus Medianeira, Paran\u00e1 85884-000, Brazil"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0107-7301","authenticated-orcid":false,"given":"Arantzazu","family":"Santamaria-Echart","sequence":"additional","affiliation":[{"name":"CIMO, LA SusTEC, Instituto Polit\u00e9cnico de Bragan\u00e7a, Campus de Santa Apol\u00f3nia, 5300-253 Bragan\u00e7a, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6844-333X","authenticated-orcid":false,"given":"Maria F.","family":"Barreiro","sequence":"additional","affiliation":[{"name":"CIMO, LA SusTEC, Instituto Polit\u00e9cnico de Bragan\u00e7a, Campus de Santa Apol\u00f3nia, 5300-253 Bragan\u00e7a, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2026,2,9]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"515","DOI":"10.1016\/j.tifs.2018.07.008","article-title":"The next Protein Transition","volume":"105","author":"Aiking","year":"2020","journal-title":"Trends Food Sci. Technol."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"370","DOI":"10.1016\/j.tplants.2023.08.006","article-title":"Microalgae: Potential Novel Protein for Sustainable Human Nutrition","volume":"29","author":"Williamson","year":"2024","journal-title":"Trends Plant Sci."},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Blanco-Llamero, C., Garc\u00eda-Garc\u00eda, P., and Se\u00f1or\u00e1ns, F.J. (2025). An Integrated Biorefinery Process to Revalorize Marine Biomass from the Microalga Nannochloropsis Gaditana Using Pressurized Green Solvents. Mar. Drugs, 23.","DOI":"10.3390\/md23070263"},{"key":"ref_4","first-page":"1","article-title":"Microalgae for Brewery Wastewater Treatment and Biomass Valorization: A Systematic Review","volume":"2025","author":"Ndiaye","year":"2025","journal-title":"Environ. Sci. Pollut. Res."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"2501488","DOI":"10.1080\/19397038.2025.2501488","article-title":"Microalgae and Circular Economy: Unlocking Waste to Resource Pathways for Sustainable Development","volume":"18","author":"Santos","year":"2025","journal-title":"Int. J. Sustain. Eng."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"133428","DOI":"10.1016\/j.biortech.2025.133428","article-title":"Microalgae Biorefinery in the Belt and Road Initiative: Opportunities for Green Growth","volume":"440","author":"Zhang","year":"2026","journal-title":"Bioresour. Technol."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"R91","DOI":"10.1016\/j.cub.2022.12.032","article-title":"Microalgae","volume":"33","author":"Muylaert","year":"2023","journal-title":"Curr. Biol."},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Gul, S., Shahnaz, L., Raiz, S., and Nawaz, M.F. (2024). Microalgae: Production, Consumption and Challenges. 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Valuable Compounds Produced by Microalgae. Handbook of Biorefinery Research and Technology: Production of Biofuels and Biochemicals, Springer Nature.","DOI":"10.1007\/978-981-97-7586-6_13"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"2203","DOI":"10.1007\/s10811-025-03536-7","article-title":"Spirulina in the 21st Century: Five Reasons for Success in Europe","volume":"37","author":"Vieira","year":"2025","journal-title":"J. Appl. Phycol."},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Prates, J.A.M. (2025). Unlocking the Functional and Nutritional Potential of Microalgae Proteins in Food Systems: A Narrative Review. Foods, 14.","DOI":"10.3390\/foods14091524"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"395","DOI":"10.2298\/JSC121020152S","article-title":"Health Aspects of Spirulina (Arthrospira) Microalga Food Supplement","volume":"78","author":"Sotiroudis","year":"2013","journal-title":"J. Serbian Chem. Soc."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"207","DOI":"10.1016\/j.biotechadv.2006.11.002","article-title":"Micro-Algae as a Source of Protein","volume":"25","author":"Becker","year":"2007","journal-title":"Biotechnol. Adv."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"107536","DOI":"10.1016\/j.biotechadv.2020.107536","article-title":"Microalgae as a Future Food Source","volume":"41","author":"Fields","year":"2020","journal-title":"Biotechnol. Adv."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"101144","DOI":"10.1016\/j.fbio.2021.101144","article-title":"Comparison of Two Strains of the Edible Cyanobacteria Arthrospira: Biochemical Characterization and Antioxidant Properties","volume":"42","author":"Mayorga","year":"2021","journal-title":"Food Biosci."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"107419","DOI":"10.1016\/j.biotechadv.2019.107419","article-title":"The Potential of Microalgae and Their Biopolymers as Structuring Ingredients in Food: A Review","volume":"37","author":"Bernaerts","year":"2019","journal-title":"Biotechnol. Adv."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Yi, X., Xie, J., and Mei, J. (2025). Recent Advances in Marine-Derived Polysaccharide Hydrogels: Innovative Applications and Challenges in Emerging Food Fields. 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Foods, 14.","DOI":"10.3390\/foods14122122"},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Ozorio, L., Passerini, A.B.S., da Silva, A.P.C., Braga, A.R.C., and Perrechil, F. (2025). Designing Plant-Based Foods: Biopolymer Gelation for Enhanced Texture and Functionality. Foods, 14.","DOI":"10.3390\/foods14091645"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"100549","DOI":"10.1016\/j.fufo.2025.100549","article-title":"The Future of Algal Proteins: Innovations in Extraction and Modifications, Functional Properties, and Sustainable Food Applications","volume":"11","author":"Pipliya","year":"2025","journal-title":"Future Foods"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"133","DOI":"10.19142\/rpq.v10i20.358","article-title":"Aspectos Gerais de Cultivo, M\u00e9todos de Secagem e Caracter\u00edsticas Da Cianobacteria Spirulina Platensis","volume":"10","author":"Sampaio","year":"2016","journal-title":"Rev. Process. Qu\u00edmicos"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"104984","DOI":"10.1016\/j.jfca.2022.104984","article-title":"Extraction of Arthrospira Platensis (Spirulina) Proteins via Osborne Sequential Procedure: Structural and Functional Characterizations","volume":"115","author":"Benelhadj","year":"2023","journal-title":"J. Food Compos. Anal."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"326","DOI":"10.1016\/j.tifs.2020.12.014","article-title":"Proteins from Microalgae for the Stabilization of Fluid Interfaces, Emulsions, and Foams","volume":"108","author":"Bertsch","year":"2021","journal-title":"Trends Food Sci. Technol."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"100445","DOI":"10.1016\/j.ijgfs.2021.100445","article-title":"Development of Ice Cream with Reduction of Sugar and Fat by the Addition of Inulin, Spirulina Platensis or Phycocyanin","volume":"27","author":"Devos","year":"2022","journal-title":"Int. J. Gastron. Food Sci."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"157","DOI":"10.47836\/ifrj.31.1.14","article-title":"Effect of Spirulina Platensis on Probiotic, Nutritional, and Quality Properties of Yogurt","volume":"31","year":"2024","journal-title":"Int. Food Res. J."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"1968","DOI":"10.1080\/10942912.2023.2238916","article-title":"Functionalization of Ricotta Cheese with Powder of Spirulina Platensis: Physicochemical, Sensory, and Microbiological Properties","volume":"26","author":"Ismail","year":"2023","journal-title":"Int. J. Food Prop."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"107650","DOI":"10.1016\/j.biotechadv.2020.107650","article-title":"Current and Novel Approaches to Downstream Processing of Microalgae: A Review","volume":"45","author":"Nitsos","year":"2020","journal-title":"Biotechnol. Adv."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"100338","DOI":"10.1016\/j.nexus.2024.100338","article-title":"Microalgal Biofuels: Challenges and Prospective in the Framework of Circular Bioeconomy","volume":"17","author":"Piyatilleke","year":"2025","journal-title":"Energy Nexus"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"109356","DOI":"10.1016\/j.foodres.2020.109356","article-title":"Spirulina for the Food and Functional Food Industries","volume":"137","author":"Lafarga","year":"2020","journal-title":"Food Res. Int."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"61","DOI":"10.1007\/s00248-024-02376-1","article-title":"A Holistic Approach to Circular Bioeconomy Through the Sustainable Utilization of Microalgal Biomass for Biofuel and Other Value-Added Products","volume":"87","author":"Ezhumalai","year":"2024","journal-title":"Microb. Ecol."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"115615","DOI":"10.1016\/j.lwt.2023.115615","article-title":"The Effect of PH and Heating on the Aggregation Behavior and Gel Properties of Beef Myosin","volume":"191","author":"Yu","year":"2024","journal-title":"LWT"},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Hydrogel, D., Roca-Arroyo, A.F., Gutierrez-Rivera, J.A., Morton, L.D., and Castilla-Casadiego, D.A. (2025). Hydrogel Network Architecture Design Space: Impact on Mechanical and Viscoelastic Properties. Gels, 11.","DOI":"10.3390\/gels11080588"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"5336","DOI":"10.1039\/D3SM00448A","article-title":"Spatially Heterogenous Dynamics in Colloidal Gels during Syneresis","volume":"19","author":"Wu","year":"2023","journal-title":"Soft Matter"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"100481","DOI":"10.1016\/j.foostr.2025.100481","article-title":"Reinforcing the Pea Protein Isolate-Gellan Gum Composite Gels by PH-Shifting Pretreatment: Emphasizing PH-Modulated Aggregation Behavior and Gelation Mechanisms","volume":"46","author":"Qi","year":"2025","journal-title":"Food Struct."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"105397","DOI":"10.1016\/j.foodhyd.2019.105397","article-title":"Modification of Heat-Induced Whey Protein Gels by Basic Amino Acids","volume":"100","author":"Wang","year":"2020","journal-title":"Food Hydrocoll."},{"key":"ref_41","doi-asserted-by":"crossref","unstructured":"Bercea, M. (2023). Rheology as a Tool for Fine-Tuning the Properties of Printable Bioinspired Gels. Molecules, 28.","DOI":"10.3390\/molecules28062766"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"112823","DOI":"10.1016\/j.foodres.2023.112823","article-title":"Rheological and Physicochemical Properties of Spirulina Platensis Residues-Based Inks for Extrusion 3D Food Printing","volume":"169","author":"Wang","year":"2023","journal-title":"Food Res. Int."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"109993","DOI":"10.1016\/j.lwt.2020.109993","article-title":"Temperature-Induced Interaction with Carboxymethyl Cellulose Affected the Rheological Properties and Structure of Wheat Gluten","volume":"133","author":"Zhao","year":"2020","journal-title":"LWT"},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"110672","DOI":"10.1016\/j.foodhyd.2024.110672","article-title":"Effect of PH-Shifting and Ultrasound on Soy\/Potato Protein Structure and Gelation","volume":"159","author":"Sun","year":"2025","journal-title":"Food Hydrocoll."},{"key":"ref_45","doi-asserted-by":"crossref","unstructured":"Kasapis, S., and Bannikova, A. (2017). Rheology and Food Microstructure. Advances in Food Rheology and Its Applications, Woodhead Publishing.","DOI":"10.1016\/B978-0-08-100431-9.00002-4"},{"key":"ref_46","doi-asserted-by":"crossref","unstructured":"Rodrigues, M.I., and Iemma, A.F. (2014). Experimental Design and Process Optimization, Crc Press.","DOI":"10.1201\/b17848"},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"1274","DOI":"10.1016\/j.lwt.2007.08.012","article-title":"Acid Thinned Jicama and Maize Starches as Fat Substitute in Stirred Yogurt","volume":"41","year":"2008","journal-title":"LWT"}],"container-title":["Molecules"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1420-3049\/31\/4\/591\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,2,11]],"date-time":"2026-02-11T05:22:33Z","timestamp":1770787353000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1420-3049\/31\/4\/591"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,2,9]]},"references-count":47,"journal-issue":{"issue":"4","published-online":{"date-parts":[[2026,2]]}},"alternative-id":["molecules31040591"],"URL":"https:\/\/doi.org\/10.3390\/molecules31040591","relation":{},"ISSN":["1420-3049"],"issn-type":[{"value":"1420-3049","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,2,9]]}}}