Effects of drying conditions on the rheological properties of reconstituted mucilage solutions (Opuntia ficus-indica)

Abstract The effects of spray drying conditions on reconstituted mucilage solutions were studied as a function of rheological properties (elastic and viscous properties) and particle size distribution (PSD). Rheological measurements were carried out at 25 °C and at concentrations of 1–6% (w/v) for spray dried and freeze dried samples. Experimental results showed that the shear viscosity slightly decreased with the increasing of inlet air temperature and atomization speed, and increased with the increasing of the feed flow rate. The Cross model was found to be the most appropriate to fit the flow curves of reconstituted mucilage solutions at concentrations ≥ 3% in spray dried samples; for freeze dried samples the Ostwald-de Waele model was better. The viscous modulus G ″ predominated over the elastic modulus G ′ for the spray dried samples, indicating a liquid-like material. The dynamic response and steady-shear measurements suggested a “random coil configuration”. The majority of the powdered samples had a mean particle diameter > 100 μm with a multimodal particle size distribution (PSD).