Forward-osmosis watermelon juice concentrate: aroma profiling and comparison to fresh fruit and thermal concentrate

Authors: Milczarek, Rebecca; SEDEJ, IVANA - Porifera

Submitted to: LWT - Food Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/13/2021
Publication Date: N/A
Citation: N/A

Interpretive Summary: Conventional watermelon juice concentrate (a syrup-like product) is produced using heat to evaporate water from the juice. This process is energy-intensive and produces undesirable flavors in the concentrate, and these off-flavors have not been well-studied in the scientific literature. Forward osmosis (FO) is a new technique for concentrating watermelon juice that does not involve heat. It thus uses less energy, and it has promise to produce concentrates that have more desirable aromas, compared to the conventional thermal concentration method. In this work, the overall aroma liking and individual aroma attributes of three samples (thermal concentrate, FO concentrate, and fresh-cut watermelon) were evaluated by a sensory (taste-testing) panel. The sensory panelists sniffed the aromas of the three samples from containers that hid the samples from view. The panelists ranked and rated the aromas for overall liking, and they used a “Check All That Apply” (CATA) response sheet to indicate which of eight possible aromas they detected in each sample. There was no significant difference in the panelists’ liking of the aromas of the FO concentrate and fresh watermelon, indicating the FO process retains the desirable aromas of fresh-cut watermelon. The thermal concentrate, in contrast, had a low liking score. From the CATA data, it was found that the off-odors “Fishy” and “Mushroom” were most associated with the thermal concentrate, while characteristic “Watermelon” aroma was most associated with the FO concentrate (even moreso than it was with fresh-cut watermelon). These results were statistically significant, but a limitation of the study is that the size of the sensory panel was somewhat small, so these results should be confirmed with a larger population. Nevertheless, the results support further development of FO for concentration of watermelon juice.

Technical Abstract: This work reports the sensory evaluation of the aroma of a forward osmosis (FO) concentrate of watermelon (Citrullus lanatus) juice. The 65° Brix concentrate was produced on a large-scale FO system without applying heat. The overall aroma liking and individual aroma attributes of the FO concentrate were compared to those of a conventional thermally-evaporated concentrate prepared from the same source juice (“thermal concentrate”), as well as to those of fresh-cut watermelon. The thermal concentrate was found to have degraded aroma quality. Sensory results showed that FO concentrate has a highly-liked aroma, and it outperformed the thermal concentrate in the sensory hedonic rating. There was no significant difference (p < 0.05) in the sensory hedonic rating between the aromas of the FO concentrate and fresh watermelon. Multiple Correspondence Analysis of aroma attributes indicated that the off-odors “Fishy” and “Mushroom” were most associated with the thermal concentrate, while characteristic “Watermelon” aroma was most associated with the FO concentrate (even moreso than it was with fresh-cut watermelon). Since the sensory panel size (N = 41) was somewhat small, these results should be confirmed with a larger population, but they are nevertheless supportive of further development of FO for concentration of watermelon juice.