ABSTRACT
Freeze-drying and spray-drying offer a clear advantage in 
obtaining products with low moisture content and high sensorial, 
nutritional and functional quality. However, powdered products 
have a high willingness to undergo changes in their physical 
properties because of environment and time. These changes are 
related to the gain of water and the effect on the physical 
state of the product. The high hygroscopicity of the powder 
products obtained from fruit juice has generated the need for 
using high molecular weight solutes acting as a barrier in 
the adsorption of water. In the present study, the sorption 
isotherms and the glass transition temperature (Tg) – water 
content relationship of two maltodextrins (4–7 y 16–19 
dextrose equivalent) and gum arabic were obtained and modeled 
and, from the thermodynamic point of view, were optimal for acting 
as hydrocolloids preservatives in the production of products with 
low humidity. On the other hand, the composition of the borojó and 
strawberry pulp was analyzed and both of them were used to obtain 
powdered products. The pulp of both fruits was freeze-dried with 
and without the addition of the characterized solutes and conditioned 
at different relative humidity levels. All samples were analyzed for 
the Tg, mechanical properties and color. In addition, the 
solubility of the obtained powder samples was studied. Tg, 
mechanical properties and color analysis were also carried 
out in commercial spray-dried products of borojó with and 
without maltodextrin 20 dextrose equivalent added. The obtained r
esults showed that the parameter that defines the loss of the quality 
of the studied powdered fruit products due to water gain was the change 
in their mechanical properties, related to the onset of caking phenomena. 
These changes occur in the samples since the glass transition starts 
and they occur before color changes done, which may be associated with 
the browning of samples. From this point of view, the low critical 
water content and water activity values of the solute-free samples 
make the incorporation of high molecular weight compounds recommended. 
Within the various solutes considered in this study, the gum arabic 
would be recommended to this end. On one hand, it is more effective 
in increasing the Tg. Moreover, it is the solute which less affects 
the color and also the one which prints a higher viscosity to the 
reconstituted product, allowing reaching an appearance and rheological 
behavior closer to that of fresh fruit pulp. Although gum arabic samples 
are less soluble than that with maltodextrin, this aspect can be improved 
by increasing the rehydration temperature to 35 ° C.