Rheological Characterization of Gofio and Aloe Vera Blended Juice

Abstract

Considering that gofio (Gf) and aloe vera juice (AVJ) have very good nutritional qualities, their combination is proposed because it is indicated as an easy and fast source of basic bio-elements. The texture of a food must be accepted by customers. This means that the rheological characteristics of the product must be known and controlled. Therefore, the influence of Gf concentration on the rheological behavior of Gf/AVJ suspensions must be determined. With continuous shear experiments, the purely viscous response of a material can be obtained. AVJ and Gf/AVJ suspensions showed shear-thinning behavior. The ability of Gf particles and aggregates to distort the flow field was quantified determining the intrinsic viscosity η of the suspensions at several shear rates using Krieger–Dougherty equation. The results indicated that the shape and size of Gf aggregates is not affected by the mechanical action due to shear. The power law (Ostwald–de Waele) model fitted the experimental steady viscosity versus shear rate values (steady viscosity curves). The flow index was less than 1, which corresponded to shear-thinning behavior. It was obtained that the flow index of AVJ maintained unaltered despite the presence of Gf particles. However, the viscosity value increased with the increasing amount of Gf as it was expected. The viscoelastic behavior of the microstructure at rest of the AVJ and Gf/AVJ suspensions was studied using oscillatory shear tests. First, linear viscoelastic response was confirmed in the relatively low amplitude shear region γ0<0.001 using an amplitude sweep shear test. After that, frequency sweep shear tests were conducted in the region where Gf/AVJ suspensions showed linear viscoelastic behavior. Varying the frequency, the response of the microstructure at rest of the suspensions when the mechanical action lasts from short to long time interval can be characterized. Jeffreys mechanical model was used for the analysis of the LVE response of Gf/AVJ suspensions. Using small amplitude oscillatory shear (SAOS) tests, it was obtained that Gf/AVJ suspensions are viscoelastic liquids that change their texture from chewy to creamy when the Gf concentration increases.