Valorization of Olive Leaves: Spray Drying of Olive Leaf Extract

Olive leaf extract has so far been used in a number of medicines, cosmetics, pharmaceuticals or even nutraceuticals. However, solid forms of plant extracts are in crescent expansion and represent several advantages over fluid extracts since the stability is improved, transport and storage become easier and higher concentration could be achieved. Thus, the objective of this work is to develop a method for exploitation of olive leaves, which will lead to the recovery of high-added value substances, based on spray drying of olive leaf extract. Olive leaves of two cultivars (Koroneiki and Chalkidiki) were used and the ultrasound method was employed for the extraction process. Concentrated olive leaf extract, with a feed rate and solids concentration of 1.75 g/min and 17% (w/w), respectively, was spray dried under different conditions of drying air temperature and flow rate and atomizing agent flow rate and product recovery data were gathered. In the case of Koroneiki cultivar, maltodextrin was used as drying agent. The resulting powders were evaluated in terms of moisture content, bulk density, hygroscopicity, and total phenolic content. The optimum operating conditions were found to be as follows: 149 and 156 °C for inlet air temperature, 21.35 and 23.10 m3/h for drying air flow rate, and 683 and 638 L/h for atomizing agent flow rate, for Chalkidiki and Koroneiki cultivar, respectively. Under these conditions, the maximum product recovery was about 71 and 73% for Chalkidiki and Koroneiki cultivar, respectively.