Desenvolvimento de material de embalagem a partir de resíduo cervejeiro

Abstract

Due to the scientific and technological advances, packaging industries that use paper, newspapers, magazines and drafts as raw material, must pay attention to new cellulosic sources for the manufacture of their products. The use of renewable natural resources comes as an alternative to this impasse, in order to develop technologies and products that have high degradation capacity without generating toxic residues. The use of agroindustrial residues generates a great interest for obtaining reinforced polymer blends, because they generally present a source of fiber and cellulose brewers’ spent grain is a by-product of the brewing industry, generated in large quantities, and one way to reduce its impact on the environment is to reuse it for the production of packaging materials. Thus, the study aimed at characterizing the brewers’ spent grain and developing packaging material from the beer residue. The centesimal composition of brewers’ spent grain, cellulose content, cellulose extraction conditions were analyzed and polymeric blends reinforced with brewers’ spent grain and addition of starch, glycerol, residual yeast from the brewing industry and glutaraldehyde in different proportions were elaborated according to the proposed fractional factorial design. The packaging material was submitted to analyses of mechanical and thermal resistance, density, water absorption and moisture. The variance, chi-square and linear regression coefficient analyses were performed, and response surface graphs were generated. As a result of the study, the by-product of the brewing industry used showed a higher proportion of fiber and protein of 39.70 and 24.83%, respectively, and a cellulose content of 9.60%, the latter increased to 26.34% after the delignification process. Thus, the delignified brewers’ spent grain was used for the production of reinforced polymer blends that presented results of tensile strength ranging from 0.0002 to 0.0065 N.mm-2, strain from 0.0058 to 0.0345, density from 174.09 to 360.44 kg.m-3, moisture from 16.24 to 98.71%, thermal conductivity from 0.0033 to 0.0559 W.m-1.K-1, and water absorption from 159.72 to 385.26%. Considering the above, it was seen that with the agroindustrial residue brewers’ spent grain, it was possible to produce reinforced polymer blends, and of the additives added, only glutaraldehyde did not show a significant positive behavior for the results. The packaging material produced proved to be capable of being a thermal insulator, for having a low thermal conductivity with variance from 0.0033 to 0.0559 W.m-1.K-1. Still, based on the tensile strength and moisture, tests 11 and 13 showed better results. These tests obtained values of RT of 0.0112 N.mm-2 and 0.0052 N.mm-2 and moisture of 18.18% and 16.24%. These tests produced packaging materials with densities of 238.95 kg.m-3 and 174.09 kg.m-3, thermal conductivity of 0.0479 W.m-1.K-1 and 0.0494 W.m-1.K-1, water absorption of 317.74% and 346.31% and deformation of 0.0102 and 0.0183.