Microencapsulation of Andes Berry (Rubus glaucus Benth.) Aqueous Extract by Spray Drying

The Andes berry (Rubus glaucus Benth.), a tropical fruit with a high anthocyanin content and pleasant aroma, was selected for spray drying to produce solids that preserve the sensory characteristics (colour, odour and taste) of the fresh fruit. A factorial design (9?×?2) was implemented to evaluate the influence of the encapsulating agent (maltodextrin DE 20, arabic gum, corn starch, yucca starch, Capsul® TA and Hi-Cap^TM 100, as well as three mixtures of them) and the nozzle diameter (1.0 and 2.0 mm) on the characteristics of solids, anthocyanin content, moisture and water activity. All solids showed water activity values (a _w) between 0.199 and 0.422, and particle size ranging from 3 to 15 μm according to microscopy results. The samples exhibiting the highest anthocyanin content were subjected to a discriminative sensory analysis. The Andes berry microencapsulates obtained with Hi-Cap^TM 100 and maltodextrin DE 20 as wall materials were chosen because of their sensory properties. The release of anthocyanins as well as volatile aroma compounds by water dissolution was confirmed by both liquid and gas chromatography coupled to mass spectrometry (HPLC-MS and GCMS, respectively). The chroma (C*ab) and a* values of the solutions were higher than those of the powders, which indicated a more intense red colour. Thermal analyses (thermogravimetric analyses and differential scanning calorimetry) showed that these two solids were stable up to 100 °C under a nitrogen atmosphere. Remarkably, the anthocyanin content did not change during 180 days at 18 °C and a relative humidity of less than 60 %. However, the shelf life of these products is highly dependent on the humidity during storage because a relative humidity increase causes significant damage to the microcapsule structures and the loss of the encapsulated materials.