The uncertainty of consumers about the toxicological effects of synthetic antioxidants incorporated into the packaging has led to a demand for natural substituents that exhibit antioxidant activity without adding risk to the consumers. In this context, the effects of adding different concentrations of thyme essential oil (TEO) (20, 30, and 40% w/w) to whey protein isolate (WPI) and cellulose nanofibre (CNF) bio-nanocomposites developed by casting were studied. Scanning electron microscopy showed a reduction in the dispersion of CNF's in all films with the addition of TEO. The addition of TEO also decreased the water vapor permeability, increased the glass transition temperature, and crystallinity index. For the mechanical properties, the addition of TEO produced less rigid and elastic films with decreased in tensile strength, elongation at break, puncture strength, puncture deformation, and elastic modulus. In addition, the mechanical properties showed the formation of non-interactive systems and the FTIR spectra showed maintenance of the phenolic compounds of the TEO after the synthesis of the films. The optical properties showed that films were less yellow (b*) with a tendency to green (a*), less saturated (c*), and less transparent when compared with the control (0% TEO). The addition of TEO to bio-nanocomposites of WPI and CNFs, in the concentration range tested, enabled the formation of materials with properties that encourage the studies for various applications.
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The authors are grateful to Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), and Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) for their financial support. Authors would like to thank Laboratory of Electron Microscopy and Analysis of Ultrastructural (https://www.prp.ufla.br/labs/microscopiaeletronica/), of Federal University of Lavras (UFLA) and Finep, Fapemig, CNPq e Capes for supplying equipment and technical support for experiments involving electron microscopy. Authors would like to thank Central of Analysis and Chemical Prospecting of UFLA and Finep, Fapemig, CNPq e Capes for supplying equipment and technical support for experiments involving FTIR and TGA analyzes.
Azevedo VM, Dias MV, Borges SV, Costa ALR, Silva EK, Medeiros ÉAA, Nilda de Fátima FS (2015) Development of whey protein isolate bio-nanocomposites: effect of montmorillonite and citric acid on structural, thermal, morphological and mechanical properties. Food Hydrocoll 48:179–188. https://doi.org/10.1016/j.foodhyd.2015.02.014CrossRefGoogle Scholar
Azevedo VM, Dias MV, Siqueira Elias de HH, Fukushima KL, Silva EK, de Deus Souza Carneiro J, de Fátima Ferreira Soares N, Borges SV (2018) Effect of whey protein isolate films incorporated with montmorillonite and citric acid on the preservation of fresh-cut apples. Food Res Int 107:306–313. https://doi.org/10.1016/j.foodres.2018.02.050CrossRefPubMedGoogle Scholar
Carvalho RA, Santos TA, de Azevedo VM, Felix PHC, Dias MV, Borges SV (2018) Bio-nanocomposites for food packaging applications: effect of cellulose nanofibers on morphological, mechanical, optical and barrier properties. Polym Int 67(4):386–392. https://doi.org/10.1002/pi.5518CrossRefGoogle Scholar
Bufalino L, de Sena Neto AR, Tonoli GHD, de Souza FA, Costa TG, Marconcini JM, Colodette JL, Labory CRG, Mendes LM (2015) How the chemical nature of Brazilian hardwoods affects nanofibrillation of cellulose fibers and film optical quality. Cellulose 22(6):3657–3672. https://doi.org/10.1007/s10570-015-0771-3CrossRefGoogle Scholar
ASTM D (1999) 3417–99. Standard test method for enthalpies of fusion and crystallization of polymers by differential scanning calorimetry (DSC). Conshohocken, Annual Book of ASTM Standards, p 02Google Scholar
ASTM A (2003) D3418–03 Standard test method for transition temperatures and enthalpies of fusion and crystallization of polymers by differential scanning calorimetry. West Conshohocken, ASTM InternationalGoogle Scholar
Jutrzenka Trzebiatowska P, Dzierbicka A, Kamińska N, Datta J (2018) The influence of different glycerine purities on chemical recycling process of polyurethane waste and resulting semi-products. Polym Int 67(10):1368–1377. https://doi.org/10.1002/pi.5638CrossRefGoogle Scholar
Lin-Vien D, Colthup NB, Fateley WG, Grasselli JG (1991) The handbook of infrared and Raman characteristic frequencies of organic molecules. Elsevier, AmsterdamGoogle Scholar
Topala CM, Tataru LD (2016) ATR-FTIR Study of thyme and rosemary oils extracted by supercritical carbon dioxide. Rev Chim (Bucharest) 67:842–846Google Scholar