Current advances in the processing optimization and quality improvement for concentrated fruit and vegetable juices

Although conventional thermal concentration has been widely used for juice processing, its operation temperature from 60 to 80 °C causes a degradation of nutritional and sensory values up to 50%, which limits the sustainable development of beverage industry. This review aims to elucidate the synergistic mechanisms of advanced concentration technologies in improving juice quality. The freeze concentration operated at sub-zero temperatures (-1 to -20 °C), has been observed to excellently retain the juice quality, while its industrial application is limited due to the high energy input and complex equipment setups. Membrane technologies, particularly forward osmosis (FO) operated at ambient temperatures (25 °C), have been utilized for juice processing due to its lower costs and good performance for enhancing the sensory and nutritional attributes of juices. Recent advancements in membrane modification and functional draw solution (DS) design have effectively increased water flux and decreased reverse solute flux (RSF), leading to a significant enhancement in concentration efficiency to 4-5 folds. This review has built up a robust theoretical foundation on the specific impacts of concentration technologies and storage conditions on sensory properties and nutritional characteristics of fruit and vegetable juices. Outcomes from this work will benefit the beverage industry from an optimization of juice processing at a low cost, securing final products with a desirable overall quality, and also accelerating the market expansion of concentrated juices.