Valorization of spent coffee grounds: Encapsulation of bioactive compounds by different drying methods

Abstract

In the present study, dryings by foam mat, foam mat freeze-drying, spray-drying and freeze-drying were proposed to microencapsulate bioactive compounds extracted from espresso spent coffee. Albumin, maltodextrin and gum arabic were used as wall materials, and the dried product was characterized and compared. The foams produced were dried in a tunnel dryer at different temperatures and air velocities. The drying time ranged from 200 to 450 min, and shorter drying times were obtained for the highest temperatures. For all drying methods, dried products with good physicochemical properties and high levels of phenolic and antioxidant compounds were obtained. The foam mat resulted in samples with higher moisture content and bulk density. On the other hand, freeze-dried samples had greater hygroscopicity and shorter wettability times. Spray-dried samples were lighter (highest value of parameter L*). The encapsulation efficiency values were between 66.46% and 88.01%, with the lowest values obtained for the foam mat.