Optimization of the conditioning and drying stages of table olive by-products to obtain new powdered ingredients

During table olive production, around 90-150 tons of fruit waste is generated as a consequence of the mechanical action of the different processing stages or due to defects in the external fruit quality, mainly consisting of olives that do not meet the required quality standards due to their size, the presence of visual defects or mechanical damage. These by-products contain interesting components such as polyphenols and monounsaturated fatty acids (MUFAs), so they may constitute an excellent raw material for obtaining new ingredients or bioactive compounds. However, table olive by-products also present a high salt content, which could hinder their subsequent incorporation into food products. So, this work aims to optimize the conditioning stage before the drying process to obtain new powdered ingredients from by-products of the table olive industry. The table olive by-products were conditioned by combining the washing and pressing stages to reduce their acidity and salt content and minimize the samples' moisture. The obtained olive paste was spread out on food-grade trays and dried in a convective drying chamber at 70 °C up to a constant weight. Thin-layer modelling was assessed to explain the drying kinetics. The results showed that the conditioning methods that included a washing stage reduced the olives' salt content by up to 75 %. The application of a pressing stage before or after washing did not affect the final salt content of the samples. Table olive powder with a reduced salt content was obtained after 5 h of drying. A combination of conditioning stages, washing and pressing before the drying process reduced the salt content in the table olive by-products, leading to new powdered ingredients that could be used by the food industry for new product development.