Exploration of food preservatives as draw solutes in the forward osmosis process for juice concentration

Forward osmosis (FO) technology has drawn increasingly research interests in juice concentration due to its great advantages in producing high-quality concentrated juice. However, the lack of suitable draw solutes is a significant obstacle hindering the practical application of FO for juice concentration. In this work, a series of food preservatives were systematically investigated as draw solutes in the FO system. By careful evaluation of these preservatives, we selected 4 M sodium diacetate (SDA) as one model of draw solution to concentrate grape juice in a 72-h continuous FO test. The concentrated grape juice with 5.14 folds was obtained with no loss of the titratable acidity and the vitamin C content. Moreover, the SDA accumulation in the concentrated product was only 2.0 ± 0.1 g/kg, after being diluted to regenerate juice, the preservative concentration in juice is 0.39 g/kg, which is lower than the safety limit of SDA (0.5 g/kg, FAO). Our findings demonstrate the application potential of the preservative draw solutions for juice concentration in the FO.