Osmotic distillation in agro-food applications

Osmotic distillation (OD), as a low-pressure osmotic-based membrane technology, is a promising approach to selectively extract water from agro-food liquid products and by-products under atmospheric pressure at room temperature, thus avoiding thermal and mechanical damage of the solute. Fruit juice concentration by osmotic distillation (OD) has been largely investigated at ITM-CNR since 1999. Conceptual process designs based on the combination of membrane-based operations with OD as final concentration step have been proposed for different fruit and vegetable juices including kiwifruit, prickly pear, orange, pomegranate and red fruit juices. Chemical composition and antioxidant activity of the fresh juice were well preserved in the final OD retentate regardless of the final content of soluble solids. Concentrated phenolic fractions of interest for nutraceutical applications have been produced by OD in order to valorize agro-food by-products, such as olive mill wastewaters (OMWs) and orange press liquors, within the logic of the circular economy. More than 84% of total phenolic compounds have been recovered from OMWs through a combination of membrane-based operations including pretreatment by microfiltration (MF), fractionation by nanofiltration (NF) and final concentration by OD. Applications of OD in wine processing industry have been also investigated to increase the amount of sugars in grape must thus improving the quality of wine obtained after fermentation without addition of non grape components as well to assess the impact of the process on the quality of partially dealcoholised (up to 4.6–5.0% v/v) and full dealcoholised (0.5% v/v) white wine.