Draw solution selection and process parameters impact the performance of forward osmosis for nonthermal concentration of liquids

Forward osmosis (FO), which is driven by the osmotic pressure difference between a highly concentrated draw solution (DS) and the liquid to be concentrated, is emerging as a solution for the nonthermal concentration of liquid foods. Identifying food grade DS with low reverse solute flux (RSF), high osmotic pressure, and low viscosity is crucial for facilitating food applications of FO. In this work, an extensive pre-screening of DS candidates for food applications, followed by experimental testing of potassium lactate, dipotassium malate, fructose, and xylitol, were conducted. A bench-top FO unit with a spiral wound cellulose triacetate membrane was used to evaluate water flux (J_w), RSF, and specific reverse solute flux (SRSF) against deionized water. The effects of feed temperature, DS temperature, and flow rate on FO were also assessed. Feed temperature and DS type significantly affected J_w and RSF. Dipotassium malate showed the highest J_w (5.3–8.8 L m⁻² h⁻¹) and the lowest RSF (19.38 ± 6.16 mg m⁻² h⁻¹) of all DS, due to its molecular weight and low viscosity. The results of this work can guide food applications of FO and help bring this technology to market.