Ésteres de amido de amêndoa de manga: síntese, caracterização e estudo de aplicabilidade em filmes para embalagens de alimento e sistemas de emulsão inversa

Abstract

After the industrial mango processing, portions of the fruit, such as peel and seed, are discarded without proper use. About 15% of the weight of mango is due to the seed, from which it is possible to obtain starch. Thus, the use of mango starch to obtain inputs that add value to industrial waste is quite promising. However, although starch is an advantageous polymer because it is biodegradable and obtained from a renewable source, it has limitations for certain industrial applications. In this context, chemical modification of the mango almond starch with vinyl laurate was carried out, with the aim of overcoming these limitations. The production of the starch esters was confirmed by infrared (IR) and nuclear magnetic resonance (NMR). The applied synthesis conditions led to the production of starch laurate with degrees of substitution 2.4 (SL1) and 0.28 (SL2). Mango almond starch showed a type A crystallinity. On the other hand, its esters lost the crystallinity pattern corresponding to the granule, presenting wide and dispersive peaks, corresponding to an amorphous material. Several mixtures of starch and starch laurate were used in the preparation of polymeric films, and their mechanical and physical properties were evaluated. Starch laurate with a high degree of substitution (SL1) was not able to form films in the conditions tested. On the other hand, starch laurate with a low degree of substitution (SL2) showed promising results. The films of starch and starch laurate mixtures, with a maximum weight concentration of 15% for SL2 (in relation to starch), prepared by microfluidization, showed greater elongation at break, greater opacity, lower stress at break and lower Young modulus than the pure starch films. The microfluidization step was decisive for obtaining films with low water vapor permeability values. In a second aspect of applicability, SL1, which was not able to form films, had its performance evaluated as a rheological modifier in an emulsion of brine in olefin, aiming application in drilling fluids. Unlike starch and SL2, SL1 showed good solubility in olefin and provided a significant increase in viscosity of the invert emulsion used as a model.