Microencapsulation by spray drying of gallic acid with nopal mucilage (Opuntia ficus indica)

The spray-drying process has been previously used to encapsulate food ingredients such as antioxidants. Thus the objective of this work was to produce microcapsules of gallic acid, a phenolic compound that acts as antioxidant, by spray drying with an aqueous extract of nopal mucilage (Ofi), which acted as an encapsulating agent. The rheological response and the particle size distribution of the final solutions containing gallic acid at concentrations of 6 g/100 mL were characterized along with the control sample, no gallic acid added, to elucidate the degree of encapsulation. The drying parameters to prepare the microcapsules with extract of nopal mucilage were: inlet air temperature (130 and 170 °C) and speed atomization (14,000 and 20,000 rpm). The rehydrated biopolymer showed a non-Newtonian pseudoplastic behavior. The Cross Model was used to model the rheological data. Values for ". m" varied between 0.55 and 0.85, and for " time characteristic,. λ", the range was between 0.0071 and 0.021 s. The mechanical spectra showed that the sample with gallic acid was stable long term (>2 days) and presented a bimodal particle size distribution. This study demonstrated the effectiveness of nopal mucilage when utilized as wall biomaterial in microencapsulation of gallic acid by the spray-drying process.