Produção de pó de banana verde e madura através da secagem em camada de espuma: otimização das condições de processo e avaliação do produto

Abstract

The drying of green and ripe banana foams with the addition of albumin was studied, considering albumin concentration (2.5; 5.0 and 7.5%), drying temperature (60, 70 and 80 °) as independent variables. C) and the thickness of the foam layer (0.8; 1.3 and 1.8 ± 0.02 cm). The experiments were carried out according to an experimental plan 33 , with 2 repetitions at the central point. The effect of albumin concentration and beat time on foam density and expansion was investigated. The drying curves were drawn and the Page and Midilli models were adjusted to the experimental data of humidity ratio as a function of time throughout the drying period and the Fick model to those of the decreasing rate period. It evaluated the effect of temperatures (60 ° C, 70 ° C, and 80 ° C) on the physical and chemical characteristics of the powders obtained from drying the foams with 5% albumin and 0.8 cm thickness. Moisture, soluble solids content, pH, proximate composition, water activity, apparent and tested density, fluidity, solubility and hygroscopicity of the powders were determined, in addition to the ascorbic acid content, phenolic compounds and antioxidant capacity. The beating time and concentration that resulted in the greatest expansion was 4 minutes and 5% albumin. A period of constant rate and another of decreasing rate were identified in all drying curves. The effects of the independent variables on the drying parameters were evaluated, observing through the statistical analysis the effect of temperature and thickness on the drying rates both in the period of constant rate, and in the average rate of drying considering the periods of constant rates and decreasing. The operating variables showed significant effects on the effective diffusivity, however, opposite effects of albumin concentration and thickness were verified for green and ripe bananas. For both fruits, the powders resulting from drying the foams and freeze-drying showed low humidity, water activity and non-hygroscopic, concluding that the characterization of the banana powders was satisfactory and is in accordance with the Brazilian standards established for agro-industrial products. Sensory analysis showed that the formulation of a vitamin with the addition of 30% of the ripe banana powder and milk did not differ in flavor from the mixture made with fresh banana and milk.