Quality of watermelon juice concentrated by forward osmosis and conventional processes

Authors: Milczarek, Rebecca; Olsen, Carl; SEDEJ, IVANA - Porifera

Submitted to: Processes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/26/2020
Publication Date: 11/28/2020
Citation: Milczarek, R.R., Olsen, C.W., Sedej, I. 2020. Quality of watermelon juice concentrated by forward osmosis and conventional processes. Processes. 8(12). Article 1568. https://doi.org/10.3390/pr8121568.
DOI: https://doi.org/10.3390/pr8121568

Interpretive Summary: Juice processors would like a way to make high-quality watermelon juice concentrate, but current concentration methods (which use heat) degrade the nutrition and flavor of the product. Forward osmosis (FO) is a new method of concentrating liquids that does not use heat. In this work, a large-scale FO system was used to make concentrate from fresh watermelon juice. The FO concentrate was compared to thermal concentrate and the source juice, as well as to commercially available refrigerated watermelon juices, in terms of several nutrients of interest and consumer liking of the juice. The FO concentrate had statistically similar levels of all the nutrients of interest except antioxidant activity, when compared to the thermal concentrate. The reconstituted (diluted back to the same water content as the source juice) FO concentrate maintained the same antioxidant activity as the raw source juice, which was 45% higher than that of the reconstituted thermal concentrate. Consumer taste-testing results showed that reconstituted FO concentrate resulted in highly-liked juice, and it outperformed the reconstituted thermal concentrate in terms of overall liking. This work demonstrates the possibility to produce a high-quality watermelon juice concentrate by forward osmosis.

Technical Abstract: Watermelon (Citrullus lanatus) juice is known for its refreshing flavor, but its high perishability limits its availability throughout the year. Watermelon juice concentrate has extended shelf-life and lower transportation and storage costs, but the conventional thermal evaporation process for concentrating juice degrades the nutritional components and sensory quality of the product. Thus, in this work, a large-scale, non-thermal forward osmosis (FO) process was used to concentrate fresh watermelon juice up to 65°Brix. The FO concentrate was compared to thermal concentrate and fresh juices, and to commercially available refrigerated watermelon juices, in terms of lycopene and citrulline content, total soluble phenolics, antioxidant activity, and sensory properties. The FO concentrate had statistically similar (p<0.05) levels of all the nutrients of interest except antioxidant activity, when compared to the thermal concentrate. The reconstituted FO concentrate maintained the same antioxidant activity as the raw source juice, which was 45% higher than that of the reconstituted thermal concentrate. Sensory results showed that reconstituted FO concentrate resulted in highly liked juice, and it outperformed the reconstituted thermal concentrate in the sensory hedonic rating. This work demonstrates the possibility to produce a high-quality watermelon juice concentrate by forward osmosis.