Using sensory and volatile analysis to investigate refreshment perceived from watermelon
Objective: The aim of this study was to identify flavor indicators for the refreshing perception of watermelon flesh and rind using sensory and flavor instrumental analysis. Methods: The sensory profile of seven watermelon varieties was defined through descriptive analysis of 11 attributes, including refreshing intensity, by a trained panel (n=9). The samples were evaluated with and without nose clips to control flavor perception. A separate assessment observed the effect of temperature. The appeal of raw rind was evaluated and its effect on the refreshing perception was determined through a consumer test (n=102) of watermelon flesh blended with 0%, 10%, 20%, and 30% w/w rind. The volatiles of watermelon flesh, rind, and blends were analyzed using solid-phase microextraction-gas chromatography mass spectrometry (SPME-GC-MS) to identify volatile compounds responsible for the refreshing perception. Results: Sensory analysis indicated that inhibition of flavor perception decreased refreshment of watermelon. Refreshing was most positively driven by wateriness, followed by crispness, fresh, melon, and sweet, negatively driven by mealiness, and cold samples were more refreshing than those at room temperature, p<0.001. The consumer test revealed that the flesh-rind blends were acceptable up to the 20% rind level. The lack of sweet and watermelon flavors, excessive green notes, perceived off flavors, and undesirable texture associated with high amounts of rind decreased hedonic and refreshing ratings. The volatile profiles of flesh and rind shared nine-carbon compounds known to impart characteristic watermelon, fresh, and green aromas, though the rind was mainly composed of only those volatiles and lacked the diversity of aldehydes, alcohols, and ketones abundant in the watermelon flesh. Conclusions: Flavor, texture, and temperature were drivers of the refreshing perception of watermelon. Watermelon rind was acceptable to consumers despite reducing watermelon flavor and the refreshing quality of flesh-rind blends. The refreshing perception was highly correlated with an abundance of nine-carbon volatiles accompanied by an assortment of other volatiles diverse in aroma. The addition of rind reduced volatile diversity of the flesh-rind blends which reduced the refreshing perception. This research demonstrated the potential for rind as a food or beverage supplement and established determinants of the refreshing perception of watermelon, which can inform fruit breeding practices and production of refreshing goods in the food industry.