ANALYSIS OF SOLUBILITY AND OPACITY IN THERMOPLASTIC BIOFILMS BASED ON STARCH AND CLAY MODIFIED BY CATION EXCHANGE

Referencia Apresentador Autores
(Instituição)
Resumo
11-047
Francisco Klebson Gomes Santos Santos, F.K.(Universidade Federal Rural do Semi-árido); Monteiro, M.K.(Universidade Federal do Rio Grande de Norte); Oliveira, V.R.(UNIVERSIDADE FEDERAL RURAL DO SEMI-ÁRIDO); Aroucha, E.M.(Universidade Federal Rural do Semi-árido); Leite, R.H.(Universidade Federal Rural do Semi-árido); de Oliveira Silva, K.N.(Universidade Federal Rual do Semi-árido); Biofilms and edible coatings are thin layers of biodegradable materials applied on food products that play an important role in their preservation, distribution and commercialization. Starch is a biopolymer produced in abundance by renewable resources. As a consequence it is easily available and cheap, being obtained after the plastification and denaturation of the native starch, on influence of the temperature in the presence of water and plasticizer, as glycerol. However, thermoplastic starch has some limitations: it is mostly soluble in water and has low thermal and mechanical resistance. The improvement of these properties was proposed in this research from the addition of 5%, by mass, of clay in relation to the dry mass of polymer. The compatibilization of the clay with the biopolymer matrix is usually accomplished through the organophilization of the clay by ion exchange reactions. In this context, it has been researched about the use of clay, in particular montmorillonite, organically modified with an organic cationic surfactant, as a filling material of biopolymer composite. Knowing this, sodium bentonite clay was chemically modified with cetyl trimethyl ammonium bromide (CETREMIDE) - organic cationic surfactant - to obtain complex clay / organic compounds, called organophilic clays. The biofilms of cassava starch with clay modified by ion exchange and not modified were characterized through XRD and FTIR. The XRD results showed the exfoliation of the modified clay and the intercalation of the unmodified clay both in relation to the biopolymer matrix, and the FTIR showed the degree of interaction between the constituents of the biofilms. The composite biofilm showed a remarkable improvement, around 34% in the solubility in relation to the natural clay biofilm. The main reason for this improvement in the composite material of starch / modified clay is the presence of organic functional groups between its lamellar interlayers which makes the polymer matrix highly compatible by polarity difference, thus, a strong interaction is obtained by reducing the porosity of the environment and contributing to the formation of a barrier on the contact surface of the biopolymer, making it hydrophobic. Thus, the crosslink density in the composite films increases with the increase of CETREMIDE content, resulting in lower solubility values. This fact alters the morphology of the starch matrix as shown by scanning electron microscopy (SEM). The opacity did not show significant variation between cassava starch biofilms with the presence of natural or modified clay. Finally, an improvement in the water dissolution property of cassava starch biofilms was obtained without altering the transparency, after the addition of a small percentage of clay modified by a cation exchange.
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