Desenvolvimento e caracterização de filmes derivados da borra de café submetida a tratamento com peróxido de hidrogênio alcalino

Abstract

Coffee is one of the worlds most popular beverages. Its consumption was about 9.3 million tons in 2016. Because of that, spent coffee grounds constitute a huge environmental issue, since about 7 million tons are generated annually and appropriate treatments for such residues are yet to be developed. Brazil is the largest coffee producer and the second consumer in the world, thus have produced almost a million tons of spent coffee grounds in 2016. Spent coffee grounds contain large amounts of organic compounds such as fatty acids, amino acids, polyphenols, minerals, and polysaccharides must amounts to approximately 50 % of the total mass. Therefore, coffee residues must be exploited as a source of value-added products. Coffee polysaccharides are excellent for biopolymer packaging development, for they are comprised mostly of galactomannans and cellulose. Researchers have been conducting plenty of studies on biomaterials in the last decades, since the accumulation of synthetic polymers has been causing serious environmental problems. Coffee galactomannan has low degree of branching and high degree of polymerization, which are good characteristics for making biopolymer films. In this research were developed films from delignified spent coffee grounds treated with alkaline peroxide hydrogen. Solutions with varied concentrations: 15, 25, 35 and 45 % (v/v). The delignified material was characterized and analysed. A zinc chloride solution was employed to dissolve the extracted galactomannans and cellulose and calcium chloride improved film properties, such as water vapour permeability and mechanical. The material from delignified spent coffee grounds treated with 35 % H2O2 has provided a better film than the others. That biomaterial presented tensile strength value of 5,971 ± 2,107 N/mm2, water vapor permeability of 1,44 ± 0,10 g.mm/m2.h.kPa and glass transition temperatura of -2,26 °C. The films presented promising characteristics, besides more researches should be done to the improvement of the properties of these biomaterials.