Optimización del secado por aspersión de mucílago de pitahaya (Hylocereus undatus) en función de sus propiedades reológicas

Abstract

Spray drying is important for biotechnology, the pharmaceutical and food industry, it can be applied to thermosensitive materials. This process allows obtain products with specific characteristics like moisture, density, particle size, solubility and rheological properties. The stabilization and conservation of pitahaya mucilage (Hylocereus undatus), a natural polymer, by spray drying to its storage and future use has not been investigated. In this study the conditions of spray drying of pitahaya mucilage were optimized, based on its rheological properties and the response surfaces obtained were analyzed. Aqueous extract of mucilage with a total concentration of 6.75g/L were used on the drier. A factorial design 23 with three central points was used to evaluate the influence of drying parameters: air inlet temperature (Te), feed flow (Fa) and atomizer speed (Va), on the yield and rheological properties of mucilage powder. The particle size distribution and moisture content of samples were determined. A sample was selected to analyze the particle morphology and to determinate its glass transition temperature (Tg). The yield had an inverse relation with air inlet temperature. The reconstituted mucilage exhibied a no-Newtonian behavior, ―shear thinning‖ (pseudoplastic), this had good fit by Cross model and important viscoelastic properties to use as thickenning. The samples showed a modal distribution and a mean particle size from 1 to 20 μm. The Tg found was higher than room temperature (48°C), the particle morphology showed the presence spherical particles forming agglomerates. The adequate conditions by spray drying of pitahaya mucilage to obtain a high yield with low moisture content of powders and rheological properties acceptable of rehydrated mucilage were: Te 130 °C, Fa de 2.2 Lh-1, y Va de 19000 rpm.