Efeitos do plasma a frio sobre filmes à base de amido, celulose bacteriana e gelatina.

Abstract

Dielectric barrier discharge (DBD) is one of the methods of generating cold plasma, which occurs between two electrodes separated by an insulating dielectric barrier. Natural polymers have been studied as alternatives to conventional plastic materials and have been gaining prominence in several studies to improve their properties in order to expand their applicability. Thus, the objective of this study is to determine the effects of the DBD plasma treatment on the surface and in the properties of interest (hydrophilic character, mechanical and barrier properties) of starch, BC (bacterial cellulose) and gelatin films.The work took place with the preparation of starch, BC and gelatin films, with plasma application in two stages, using atmospheric air, and varying time and frequency for each matrix. The films were characterized before and after treatment (Contact Angle, Water Solubility, Fourier Transform Infrared Spectroscopy - FTIR, Chemometric Analysis, Scanning Electron Microscopy – SEM, Mechanical Properties and Water Vapor Permeability - WVP). The starch film showed a significant increase in contact angle measurements, which indicate an increase in hydrophobicity when exposed to 200 Hz for 20 min. For BC and gelatin films, the greatest variation in hydrophobicity was observed in the tests using higher frequency (950 Hz) for 20 min. The insolubility percentages of the films remained high, 90% and 71% for the BC and gelatin films, respectively. The starch film, although having its insoluble matter content increased three-fold continued to show a high level of water solubility, which makes it difficult to use for foods with high water activity, for example. Chemometrics showed that the BC film was the least susceptible to plasma, when compared to the starch and gelatin films, a result corroborated with the other analyzes made. The barrier properties were not affected by the DBD plasma under the studied conditions. However, the starch and gelatin films showed better mechanical performance after treatment. The effects of plasma on the performance of the films suggest that this technology has the potential to modify its properties, according to the frequency range and time used for each matrix.