Thermal and microstructural stability of a powdered gum derived from Pereskia aculeata Miller leaves

Abstract

In this report, the thermal and microstructural stability of a powdered product derived from Pereskia aculeata Miller (the Barbados gooseberry), popularly known in Brazil as ora-pro-nobis (OPN), was characterized. Using optimized processing conditions, a gum was prepared, and its proximate compo- sition, mineral content, thermal stability (using differential scanning calorimeter, DSC and thermog- ravimetry, TG), microstructure (using scanning electron microscopy, SEM), energy-dispersive x-ray spectrum and emulsion-formation capacity (using optical microscopy) were determined. The stability of various emulsions was evaluated at room temperature and at 80 C. The powdered product had high protein and mineral contents. The DSC thermal profile of the OPN powdered product showed endo- thermic and exothermic events that reflected the organizational system and sample destruction, respectively. The TG curves for the OPN gum products revealed high residual values, which were attributable to their carbonaceous and mineral contents. SEM micrographs of the powdered OPN gum demonstrated a high level of porosity, particles of different sizes and smaller particles adherent to larger particles. The spongy structure suggested that this material displayed hygroscopic behavior. SEM/energy- dispersive x-ray spectrometry confirmed that large quantities of minerals were present in the samples. The emulsion-formation capacity of the product was evaluated and showed that the coalescence of droplets was proportional to the decrease in the concentration of the powdered gum. Protein and car- bohydrate macromolecules in the OPN gum were identified using fluorescence microscopy.