Evaluation of the adsorption behavior of freeze-dried passion fruit pulp with added carriers by traditional biospeckle laser techniques

Abstract

This work was aimed to evaluate the potential of the biospeckle laser technique to monitor the sorption behavior of freeze-dried passion fruit pulp. For this purpose, passion fruit pulp with carriers (sucrose, fructose, maltodextrin, and ethanol) was added at different concentrations and combinations were freeze dried, and their sorption behavior was monitored in environments with relative humidities of 0.113, 0.529, 0.753, and 0.903 by gravimetric and biospeckle laser analyses. The thermal and structural stabilities of the powders were evaluated using differential scanning calorimetry and scanning electron microscopy. The biospeckle laser tool was capable of monitoring the water activity present in the passion fruit powders at relative humidities of 0.113, 0.529, and 0.753. In a relative humidity of 0.113, adsorption was slow, and the speckle pattern was altered regardless of the added carrier. Relative humidities of 0.529 and 0.753 resulted in an adsorption behavior and altered speckle pattern, which were variable, i.e., they were dependent upon the added carriers. At a relative humidity of 0.903, the adsorbed mass of water and alterations in the speckle pattern over time were intense. Ethanol furthered the degree of organization of the structures in the crystallization process. Maltodextrin was effective at stabilizing the passion fruit powders, resulting in poorer water adsorption and increased vitreous transition temperature. Fructose promoted typically amorphous freeze-dried powders, due to the high glass transition temperature and the formation of highly sticky tubular and roundish structure.