{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,30]],"date-time":"2026-09-30T03:01:25Z","timestamp":1790737285823,"version":"4.1.0"},"reference-count":56,"publisher":"MDPI AG","issue":"21","license":[{"start":{"date-parts":[[2022,10,25]],"date-time":"2022-10-25T00:00:00Z","timestamp":1666656000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Engineering and Physical Sciences Research Council","award":["EP\/V027654\/1-EP\/R512436\/1"],"award-info":[{"award-number":["EP\/V027654\/1-EP\/R512436\/1"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>Fast-moving consumer goods (FMCG) industry has long included many appealing essential oils in products to meet consumers\u2019 needs. Among all, the demand for limonene (LM) has recently surged due to its broad-spectrum health benefits, with applications in cosmetic, detergent, and food products. However, LM is extremely volatile, hence has often been encapsulated for a longer shelf-life. To date, mostly non-biodegradable synthetic polymers have been exploited to fabricate the microcapsule shells, and the resulting microcapsules contribute to the accumulation of microplastic in the environment. So far, information on LM-entrapping microcapsules with a natural microplastic-free shell and their mechanism of formation is limited, and there is lack of an in-depth characterisation of their mechanical and adhesive properties, which are crucial for understanding their potential performance at end-use applications. The present research aims towards developing safe microcapsules with a core of LM fabricated via complex coacervation (CC) using gum Arabic (GA) and fungally sourced chitosan (fCh) as shell precursors. The encapsulation efficiency (EE) for LM was quantified by gas chromatography (GC) separation method. The morphology of microcapsules was investigated via bright-field optical microscopy and scanning electron microscopy, and their mechanical properties were characterised using a micromanipulation technique. Moreover, the adhesive properties of the resulting microcapsules were studied via a bespoke microfluidic device fitted with a polyethylene-terephthalate (PET) substrate and operating at increasingly hydrodynamic shear stress (HSS). Spherical core-shell microcapsules (EE ~45%) with a mean size of 38 \u00b1 2 \u03bcm and a relatively smooth surface were obtained. Their mean rupture force and nominal rupture stress were 0.9 \u00b1 0.1 mN and 2.1 \u00b1 0.2 MPa, respectively, which are comparable to those of other microcapsules with synthetic shells, e.g., urea- and melamine-formaldehyde. It was also found that the fCh-GA complexed shell provided promising adhesive properties onto PET films, leading to a microcapsule retention of ~85% and ~60% at low (\u226450 mPa) and high shear stress (0.9 Pa), respectively. Interestingly, these values are similar to the adhesion data available in literature for microplastic-based microcapsules, such as melamine-formaldehyde (50\u201390%). Overall, these findings suggest that microplastics-free microcapsules with a core of oil have been successfully fabricated, and can offer a potential for more sustainable, consumer- and environmentally friendly applications in FMCGs.<\/jats:p>","DOI":"10.3390\/molecules27217215","type":"journal-article","created":{"date-parts":[[2022,10,26]],"date-time":"2022-10-26T02:47:26Z","timestamp":1666752446000},"page":"7215","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":25,"title":["Microplastic-Free Microcapsules to Encapsulate Health-Promoting Limonene Oil"],"prefix":"10.3390","volume":"27","author":[{"given":"Daniele","family":"Baiocco","sequence":"first","affiliation":[{"name":"School of Chemical Engineering, University of Birmingham, Birmingham B15 2TT, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Zhibing","family":"Zhang","sequence":"additional","affiliation":[{"name":"School of Chemical Engineering, University of Birmingham, Birmingham B15 2TT, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2022,10,25]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Ib\u00e1\u00f1ez, M.D., Sanchez-Ballester, N.M., and Bl\u00e1zquez, M.A. (2020). Encapsulated limonene: A pleasant lemon-like aroma with promising application in the agri-food industry. A review. Molecules, 25.","DOI":"10.3390\/molecules25112598"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"254","DOI":"10.1007\/s11418-021-01553-7","article-title":"Diversity in principal constituents of plants with a lemony scent and the predominance of citral","volume":"76","author":"Hirai","year":"2022","journal-title":"J. Nat. Med."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"668","DOI":"10.1016\/j.fct.2018.07.052","article-title":"Review of toxicological assessment of d-limonene, a food and cosmetics additive","volume":"120","author":"Ravichandran","year":"2018","journal-title":"Food Chem. Toxicol."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"e13566","DOI":"10.1111\/jfbc.13566","article-title":"D-limonene: A multifunctional compound with potent therapeutic effects","volume":"45","author":"Anandakumar","year":"2021","journal-title":"J. Food Biochem."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"100016","DOI":"10.1016\/j.fhfh.2021.100016","article-title":"Microcapsules with a fungal chitosan-gum arabic-maltodextrin shell to encapsulate health-beneficial peppermint oil","volume":"1","author":"Baiocco","year":"2021","journal-title":"Food Hydrocoll. Health"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"31","DOI":"10.1007\/s12156-010-0066-8","article-title":"D-Limonene: A bioactive food component from citrus and evidence for a potential role in breast cancer prevention and treatment","volume":"5","author":"Miller","year":"2011","journal-title":"Oncol. Rev."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"2339","DOI":"10.3892\/mmr.2017.6241","article-title":"D-limonene exhibits anti-inflammatory and antioxidant properties in an ulcerative colitis rat model via regulation of iNOS, COX-2, PGE2 and ERK signaling pathways","volume":"15","author":"Yu","year":"2017","journal-title":"Mol. Med. Rep."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"19","DOI":"10.1614\/WS-D-16-00044.1","article-title":"Herbicidal activity of monoterpenes is associated with disruption of microtubule functionality and membrane integrity","volume":"65","author":"Chaimovitsh","year":"2017","journal-title":"Weed Sci."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"989","DOI":"10.1007\/s11101-017-9512-6","article-title":"Phytochemical biopesticides: Some recent developments","volume":"16","author":"Walia","year":"2017","journal-title":"Phytochem. Rev."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"126861","DOI":"10.1016\/j.colsurfa.2021.126861","article-title":"Encapsulation of hexylsalicylate in an animal-free chitosan-gum arabic shell by complex coacervation","volume":"625","author":"Baiocco","year":"2021","journal-title":"Colloids Surf. A: Physicochem. Eng. Asp."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"40","DOI":"10.1111\/1541-4337.12006","article-title":"Stability of Essential Oils: A Review","volume":"12","author":"Turek","year":"2013","journal-title":"Compr. Rev. Food Sci. Food Saf."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"155","DOI":"10.1016\/j.jcis.2020.01.115","article-title":"Improved volatile cargo retention and mechanical properties of capsules via sediment-free in situ polymerization with cross-linked poly(vinyl alcohol) as an emulsifier","volume":"568","author":"Zhang","year":"2020","journal-title":"J. Colloid Interface Sci."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"123028","DOI":"10.1016\/j.cej.2019.123028","article-title":"Hydrocolloids: Nova materials assisting encapsulation of volatile phase change materials for cryogenic energy transport and storage","volume":"382","author":"Zhang","year":"2020","journal-title":"Chem. Eng. J."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"129185","DOI":"10.1016\/j.chemosphere.2020.129185","article-title":"Accumulation of microcapsules derived from coated fertilizer in paddy fields","volume":"267","author":"Katsumi","year":"2021","journal-title":"Chemosphere"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"691","DOI":"10.1016\/j.bjp.2014.11.007","article-title":"Properties and controlled release of chitosan microencapsulated limonene oil","volume":"24","author":"Souza","year":"2014","journal-title":"Rev. Bras. De Farmacogn."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"17","DOI":"10.1002\/ffj.1911","article-title":"Formation and characterization of microcapsules by complex coacervation with liquid or solid aroma cores","volume":"24","author":"Leclercq","year":"2009","journal-title":"Flavour Fragr. J."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"272","DOI":"10.1016\/j.foodchem.2013.08.074","article-title":"Development and evaluation of novel flavour microcapsules containing vanilla oil using complex coacervation approach","volume":"145","author":"Yang","year":"2014","journal-title":"Food Chem"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"110676","DOI":"10.1016\/j.eurpolymj.2021.110676","article-title":"Preparation and antimicrobial activity of pectin-chitosan embedding nisin microcapsules","volume":"157","author":"Qian","year":"2021","journal-title":"Eur. Polym. J."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"50482","DOI":"10.1002\/app.50482","article-title":"Chitosan microcapsules: Methods of the production and use in the textile finishing","volume":"138","author":"Valle","year":"2021","journal-title":"J. Appl. Polym. Sci."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Haave, M., Gomiero, A., Sch\u00f6nheit, J., Nilsen, H., and Olsen, A.B. (2021). Documentation of microplastics in tissues of wild coastal animals. Front. Environ. Sci., 9.","DOI":"10.3389\/fenvs.2021.575058"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"118522","DOI":"10.1016\/j.envpol.2021.118522","article-title":"Microplastics impact shell and pearl biomineralization of the pearl oyster Pinctada fucata","volume":"293","author":"Han","year":"2022","journal-title":"Environ. Pollut."},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Cverenk\u00e1rov\u00e1, K., Valachovi\u010dov\u00e1, M., Macku\u013eak, T., \u017demli\u010dka, L., and B\u00edro\u0161ov\u00e1, L. (2021). Microplastics in the food chain. Life, 11.","DOI":"10.3390\/life11121349"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"51","DOI":"10.1016\/j.jiec.2020.12.001","article-title":"Biodegradability evaluation of hydroxyethylcellulose-based microcapsules by 1h nuclear magnetic resonance spectroscopy","volume":"95","author":"Kim","year":"2021","journal-title":"J. Ind. Eng. Chem."},{"key":"ref_24","unstructured":"Baiocco, D. (2021). Fabrication and Characterisation of Vegetable Chitosan Derived Microcapsules. [PhD Thesis, University of Birmingham]."},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Jones, M., Kujundzic, M., John, S., and Bismarck, A. (2020). Crab vs. Mushroom: A review of crustacean and fungal chitin in wound treatment. Mar Drugs, 18.","DOI":"10.3390\/md18010064"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"1458","DOI":"10.1002\/pi.4941","article-title":"Scent properties by natural fragrance microencapsulation for footwear applications","volume":"64","year":"2015","journal-title":"Polym. Int."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"593","DOI":"10.1080\/02652040010019541","article-title":"Mechanical properties of melamine-formaldehyde microcapsules","volume":"18","author":"Sun","year":"2001","journal-title":"J. Microencapsul."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"150","DOI":"10.1002\/jssc.201900770","article-title":"Gas chromatography vacuum ultraviolet spectroscopy: A review","volume":"43","author":"Lelevic","year":"2020","journal-title":"J. Sep. Sci."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"4142","DOI":"10.1021\/ie800090c","article-title":"Microencapsulation of limonene for textile application","volume":"47","author":"Rodrigues","year":"2008","journal-title":"Ind. Eng. Chem. Res."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"603","DOI":"10.3109\/02652049409051110","article-title":"Production of oil-containing polyterephthalamide microcapsules by interfacial polymerization. An experimental investigation of the effect of process variables on the microcapsule size distribution","volume":"11","author":"Alexandridou","year":"1994","journal-title":"J. Microencapsul."},{"key":"ref_31","unstructured":"Kulkarni, V.S. (2010). Chapter III\u2014Emulsions and microemulsions for topical and transdermal drug delivery. Handbook of Non-Invasive Drug Delivery Systems, William Andrew Publishing."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"101","DOI":"10.1016\/j.colsurfa.2005.04.015","article-title":"Emulsion microstructure and energy input, roles in emulsion stability","volume":"262","author":"Liu","year":"2005","journal-title":"Colloids Surf. A: Physicochem. Eng. Asp."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"10209","DOI":"10.1021\/jp801756q","article-title":"Encapsulation of Pt nanoparticles as a result of strong metal\u2212support interaction with Fe3O4 (111)","volume":"112","author":"Qin","year":"2008","journal-title":"J. Phys. Chem. C"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"10","DOI":"10.1016\/j.jcis.2016.08.058","article-title":"J, The effect of surfactant chain length on the morphology of poly(methyl methacrylate) microcapsules for fragrance oil encapsulation","volume":"484","author":"Tasker","year":"2016","journal-title":"J. Colloid Interface Sci."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"49","DOI":"10.1016\/j.colsurfa.2018.06.022","article-title":"Predicting microcapsules morphology and encapsulation efficiency by combining the spreading coefficient theory and polar surface energy component","volume":"554","author":"Szczotok","year":"2018","journal-title":"Colloids Surf. A: Physicochem. Eng. Asp."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"5516","DOI":"10.1021\/acs.iecr.7b00741","article-title":"Aroma-loaded microcapsules with antibacterial activity for eco-friendly textile application: Synthesis, characterization, release, and green grafting","volume":"56","author":"Sharkawy","year":"2017","journal-title":"Ind. Eng. Chem. Res."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"108","DOI":"10.1016\/j.jfoodeng.2017.08.026","article-title":"Preparation and characterization of citrus essential oils loaded in chitosan microcapsules by using different emulsifiers","volume":"217","author":"Li","year":"2018","journal-title":"J. Food Eng."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"191","DOI":"10.1016\/j.cej.2014.02.024","article-title":"Microencapsulation of essential oils with biodegradable polymeric carriers for cosmetic applications","volume":"245","author":"Martins","year":"2014","journal-title":"Chem. Eng. J."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"940","DOI":"10.1039\/B606965G","article-title":"Formation of liquid core\u2013polymer shell microcapsules","volume":"2","author":"Yow","year":"2006","journal-title":"Soft Matter R. Soc. Chem."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"172","DOI":"10.1039\/B911541B","article-title":"Interfacial tension between a complex coacervate phase and its coexisting aqueous phase","volume":"6","author":"Spruijt","year":"2010","journal-title":"Soft Matter R. Soc. Chem."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"40","DOI":"10.1016\/j.partic.2015.09.003","article-title":"Composite microcapsules with enhanced mechanical stability and reduced active ingredient leakage","volume":"26","author":"Long","year":"2016","journal-title":"Particuology"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"6882","DOI":"10.1039\/b902832c","article-title":"Microcapsules with low content of formaldehyde: Preparation and characterization","volume":"19","author":"Long","year":"2009","journal-title":"J. Mater. Chem."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"2042","DOI":"10.1016\/j.ces.2011.01.015","article-title":"Determination of the elastic properties of single microcapsules using micromanipulation and finite element modeling","volume":"66","author":"Nguyen","year":"2011","journal-title":"Chem. Eng. Sci."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"32","DOI":"10.1016\/j.partic.2015.06.002","article-title":"Determination of microcapsule physicochemical, structural, and mechanical properties","volume":"24","author":"Gray","year":"2016","journal-title":"Particuology"},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"1563","DOI":"10.1177\/0021998314536070","article-title":"Effect of specimen history on structure and in-plane permeability of woven fabrics","volume":"49","author":"Endruweit","year":"2014","journal-title":"J. Compos. Mater."},{"key":"ref_46","unstructured":"Liu, S. (2018). Understanding Molecular Interactions to Enhance Deposition of Perfume Microcapsules on Fabric Surfaces. [PhD Thesis, University of Birmingham]."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"608","DOI":"10.1016\/j.carbpol.2013.09.006","article-title":"Preparation of microcapsules by complex coacervation of gum Arabic and chitosan","volume":"99","author":"Butstraen","year":"2014","journal-title":"Carbohydr. Polym."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"1762","DOI":"10.1080\/01932691.2011.625523","article-title":"Dynamic light scattering based microelectrophoresis: Main prospects and limitations","volume":"33","year":"2012","journal-title":"J. Dispers. Sci. Technol."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"114426","DOI":"10.1016\/j.molliq.2020.114426","article-title":"Effect of pH and surfactants on the electrokinetic properties of nanoparticles dispersions and their application to the PET fibres modification","volume":"320","author":"Kowalczyk","year":"2020","journal-title":"J. Mol. Liq."},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"310","DOI":"10.1016\/j.dyepig.2015.07.004","article-title":"Effect of N-cetylpyridinium chloride in adsorption of graphene oxide onto polyester","volume":"122","author":"Moleon","year":"2015","journal-title":"Dye. Pigment."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"973","DOI":"10.1080\/01694243.2012.727169","article-title":"Measurement of the adhesion between single melamine-formaldehyde resin microparticles and a flat fabric surface using AFM","volume":"27","author":"Liu","year":"2013","journal-title":"J. Adhes. Sci. Technol."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"138","DOI":"10.1006\/jcis.2002.8388","article-title":"Interactions between acid- and base-functionalized surfaces","volume":"252","author":"Giesbers","year":"2002","journal-title":"J. Colloid Interface Sci."},{"key":"ref_53","first-page":"3349","article-title":"Parallel-plate flow chamber and continuous flow circuit to evaluate endothelial progenitor cells under laminar flow shear stress","volume":"59","author":"Lane","year":"2012","journal-title":"J. Vis. Exp."},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"800","DOI":"10.1205\/cherd06082","article-title":"Evaluating the adhesion force between saccharomyces cerevisiae yeast cells and polystyrene from shear-flow induced detachment experiments","volume":"85","author":"Guillemot","year":"2007","journal-title":"Chem. Eng. Res. Des."},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"1101","DOI":"10.1007\/s10439-010-0221-1","article-title":"Nucleus pulposus cell response to confined and unconfined compression implicates mechanoregulation by fluid shear stress","volume":"39","author":"Wang","year":"2011","journal-title":"Ann. Biomed. Eng."},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"8041","DOI":"10.1021\/acssuschemeng.9b00677","article-title":"Sustainable chemistry considerations for the encapsulation of volatile compounds in laundry-type applications","volume":"7","author":"Bruyninckx","year":"2019","journal-title":"ACS Sustain. Chem. Eng."}],"container-title":["Molecules"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1420-3049\/27\/21\/7215\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T01:02:05Z","timestamp":1760144525000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1420-3049\/27\/21\/7215"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,10,25]]},"references-count":56,"journal-issue":{"issue":"21","published-online":{"date-parts":[[2022,11]]}},"alternative-id":["molecules27217215"],"URL":"https:\/\/doi.org\/10.3390\/molecules27217215","relation":{},"ISSN":["1420-3049"],"issn-type":[{"value":"1420-3049","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,10,25]]}}}