Efeito da concentração de plastificante em revestimentos comestíveis à base de blendas de poli(álcool vinílico) (PVA) e amido catiônico (CS)

Abstract

Films based on poly(vinyl alcohol) (PVA) and cationic starch (CS) were combined with different percentages of sorbitol (S) to evaluate the effect of the plasticizer on the properties of the films. FTIR and DRX analyzes confirmed the interaction between them. However, SEM micrographs confirmed the formation of sorbitol crystals on the surface of the films. These crystals became more evident with increasing amount of sorbitol. The polymer/sorbitol mixture is stable for a short period. The mixtures showed low values of water vapor transmission rate, reaching (7.703 ± 0.00) g h-1 m-2 and low solubility values for films containing higher amounts of CS. The lack of statistical differences in most parameters suggests that increasing the amount of sorbitol does not promote any significant gain in percentages greater than 15% m/m. As a coating, the mixture composed of 75% PVA, 25% CS and 15% S successfully reduced moisture loss in the acerolas, and preserved the bright red color of the fruits for longer periods. In addition, the coating led to a more homogeneous maturation, and increased the shelf life of the acerolas by one day (temperature of 25ºC). This confirms the suitability of this mixture for food coating purposes.