# Watermelon Rind and Flesh Volatile Profiles and Cultivar Difference
## 4 Discussion
Esters, however, are not the major grouped compounds in watermelon and only several esters have been identified in this study as well in literature [28; 37]. Our current study identified two lactones. \(\gamma\)-Nonalactone had low peak abundance, but potentially, it could contribute sweet, creamy notes to watermelon. Volatile organic acids are barely found in watermelon literature. One of five acids identified in this study, hexanoic acid, might contribute fatty, cheesy notes to watermelon, though these notes are minimal for watermelon organoleptic characteristics. Three sulfur compounds were identified in this study, while many more have been identified by other researchers [28; 38; 39]. Sulfur compounds are considered off-notes for watermelon, especially processed watermelon juice [28; 39]. In the present study, rind and flesh samples of different varieties differed significantly in their total volatile abundance. Results also showed that different watermelon varieties were differentiated by their volatile profile percentages of aldehydes, alcohols, and ketones (especially for flesh), indicating that volatiles are linked to the genetics of watermelon. The findings are in line with other researchers stating significant variation in the amounts and profiles of volatile among genotypes and fruit fractions [3; 40; 41]. Literature specifically pertaining to watermelon volatile variety difference is very limited. The total volatile content of five watermelon varieties was found to vary by a factor of up to one time [3]. Additionally, different parts of the watermelon contain different bioactive compound concentrations and antioxidant activities [41]; however, volatiles in different parts of watermelon have not yet been analyzed. Volatiles in the rind and flesh of four watermelon cultivars (Captivation, Exclamation, Excursion, and Fascination) were identified in this study for the first time, though their sensory profiles have been reported previously [30]. Horticultural traits of Captivation, Exclamation, and Fascination have also been reported [42; 43; 44]. Watermelon find has advantages of high citrulline content compared to flesh [14], and contained major volatile compounds of nine-carbon aldehydes and alcohols as identified in this study. The results of the major nine-carbon volatiles in mind from the current study bring in a new potential use of watermelon rind; for example, watermelon rind might be used in highly nutritive plant waters, which could be marketed as consumer hydration options, with fresh, green flavor notes imparted by watermelon rind [45]. It should be pointed out that our previous consumer test shows that high amounts of watermelon rind imparts excessive green notes and off-flavor, negatively correlating with consumer hedonic rating [45]. The previous study also shows refreshing perception of watermelon juice blended with rind [45]. Combined our previous sensory study with this rind volatile study, it could be deduced that watermelon rind has the potential to impart refreshing perception in food products due to its high nine-carbon volatile content. Fruit volatiles are mainly association with aroma contribution, instead of other functions such as refreshing perception. The relationship between watermelon rind volatiles and refreshing perception is an interesting area, which should be further verified in future studies.