Abstract
Spray-drying is a suitable method for drying carob juice, a popular drink, without a significant loss in beneficial nutritional properties or powder wetting behaviour. Maltodextrin (MD) was used as a wall material at different concentrations, namely 5, 10, 20 and 30% (MD dry solids/100 g feed mixture dry solids). Physical properties including moisture content, pH, titratable acidity, total soluble solids, and colour parameters were studied for the feed samples as well as the samples reconstituted after spray-drying. Moreover, the product yield, bulk density, and powder particle solubility were evaluated, as were their morphology and extent of nonenzymatic browning based on furfural content by using scanning electron microscopy (SEM) and solid-phase microextraction/gas chromatography-mass spectrometry (SPME/GC-MS). The increment in MD content increased the yield, solubility, and moisture, and decreased the bulk density of the spray-dried powder. Simultaneously, MD addition caused a decrease in pH values with an increase in the total soluble solids and titratable acidity of the reconstituted samples in comparison to the feed ones. As the MD to juice ratio increased, the lightness of the powders increased (L*), while both colour parameters a* and b* decreased. Furfural extraction using SPME, followed by GC-MS analysis, showed a decrease in furfural concentration with the addition of MD. The presence of MD as the main carrier agent at a concentration of 20-30% enabled the formation of more homogeneous capsules with a better spherical shape and smoother surface, as observed under SEM. Therefore, MD can be successfully used at a 20-30% concentration to spray-dry carob juice and formulate an instant drink without any drawbacks.