ABSTRACT High-sugar dehydrated foods have strong hygroscopicity, which can be avoided by using drying aids. One way to assess the hygroscopic behavior is through sorption isotherms. The objective of this work was to evaluate the influence of maltodextrin concentration on sorption isotherms of powdered cajá-manga pulp in spray-dryer, lyophilization and fluidized bed spray drying processes. The dryings were carried out in a spray-dryer, lyophilizer and fluidized bed, with 10%, 20% and 30% of maltodextrin. Adsorption isotherms were determined by the static gravimetric method using salt solutions for a relative humidity range of 21% to 90%. The GAB, BET, Henderson, and Oswin models were adequate to the experimental data. The relative deviation between the experimental values and the estimated values was calculated for each curve, in order to assess which equation best fit the experimental data. The mean relative error value of less than 10% was considered one of the criteria for selecting the models. The BET (A), BET (B) and GAB (C) models had the lowest error means, 3.35%, 3.35% and 5.28%, for cajá-manga powders obtained by spray-dryer, lyophilization and fluidized bed spray drying processes, respectively, and coefficients of determination above 0.99. It is concluded that the type of drying process did not influence the behavior of the adsorption isotherms, and that increases in maltodextrin concentration and temperature are significant in reducing equilibrium moisture contents. Highsugar High sugar hygroscopicity aids cajámanga cajá manga spraydryer, spraydryer dryer, dryer spray-dryer processes 10 20 30 21 90 90% Henderson data curve A, A , (A) B (B C (C means 335 3 35 3.35 528 5 28 5.28% respectively 099 0 99 0.99 contents 1 2 9 (A 33 3.3 52 5.28 09 0.9 3. 5.2 0. 5.

RESUMO O objetivo deste trabalho foi o estudo de estabilidade da polpa de manga em pó obtida pelo processo de liofilização, assim como das suas características estruturais através de análise de microscopia eletrônica. Em resposta ao delineamento experimental realizado precedentemente utilizando concentrações de maltodextrina de 0%; 10%; 20% e 30% e tempos de 24 e 30 horas, foi escolhida a condição de 20% de maltodextrina e 24 horas de secagem como a melhor para secagem de manga em liofilizador. Portanto, o estudo de estabilidade foi realizado com a polpa de manga em pó obtida a partir desta melhor condição de secagem armazenada durante 90 dias, com acompanhamento quinzenal através de realização das análises de umidade, teor de ácido ascórbico, parâmetro colorimétrico b* e higroscopicidade. O armazenamento foi feito a temperatura ambiente (27 ºC) em embalagem laminada com e sem vácuo, e plástica sem vácuo. A embalagem laminada a vácuo apresentou maior manutenção das características iniciais do produto armazenado, principalmente para o teor de ácido ascórbico, higroscopicidade e parâmetro de cor b*. Posteriormente foi realizado o estudo da microestrutura da amostra em diferentes concentrações de maltodextrina (0%; 10%; 20% e 30%) com finalidade de compreender a interferência do adjuvante no produto final. As imagens aproximadas do pó revelaram a formação de superfície porosa e a influência do adjuvante nas dimensões da partícula, na qual maiores concentrações de maltodextrina resultaram em pós de menores e mais porosos.

ABSTRACT The aim of this work was to study the stability of powdered mango pulp obtained through the process of lyophilisation, as well as its structural characteristics using electron microscopy analysis. In response to an earlier experimental design using maltodextrin concentrations of 0%, 10%, 20% and 30% and periods of 24 and 30 hours, the condition of 20% maltodextrin and 24 hours drying was chosen as the best for drying mango in a freeze dryer. The stability study was therefore carried out using powdered mango pulp obtained under the above best-drying conditions, stored for 90 days and monitored every two weeks by analysis of the moisture, ascorbic acid content, b* colorimetric parameter and hygroscopicity. Storage was at room temperature (27 °C) in vacuum and non-vacuum laminated packaging, and in non-vacuum plastic packaging. The vacuum laminated packaging maintained the initial characteristics of the stored product for longer, especially the ascorbic acid content, hygroscopicity and b* colour parameter. The microstructure of the sample was then studied under different concentrations of maltodextrin (0%, 10%, 20% and 30%) so as to understand the effect of the drying agent on the final product. Close-up images of the powder revealed the porous surface formation and the effect of the agent on particle size, where higher concentrations of maltodextrin resulted in more porous powders with smaller particles.