High Glucosinolate Content in Rocket Leaves (Diplotaxis tenuifolia and Eruca sativa) after Multiple Harvests Is Associated with Increased Bitterness, Pungency, and Reduced Consumer Liking

Abstract

Rocket (Diplotaxis tenuifolia and Eruca sativa) leaves delivered to the UK market are variable in appearance, taste, and flavour over the growing season. This study presents sensory and consumer analyses of rocket produce delivered to the UK over the course of one year, and evaluated the contribution of environmental and cultivation factors upon quality traits and phytochemicals called glucosinolates (GSLs). GSL abundance was positively correlated with higher average growth temperatures during the crop cycle, and perceptions of pepperiness, bitterness, and hotness. This in turn was associated with reduced liking, and corresponded to low consumer acceptance. Conversely, leaves with greater sugar content were perceived as more sweet, and had a higher correlation with consumer acceptance of the test panel. First cut leaves of rocket were favoured more by consumers, with multiple leaf cuts associated with low acceptance and higher glucosinolate concentrations. Our data suggest that the practice of harvesting rocket crops multiple times reduces consumer acceptability due to increases in GSLs, and the associated bitter, hot, and peppery perceptions some of their hydrolysis products produce. This may have significant implications for cultivation practices during seasonal transitions, where leaves typically receive multiple harvests and longer growth cycles.

Effects of Growing Cycle and Genotype on the Morphometric Properties and Glucosinolates Amount and Profile of Sprouts, Microgreens and Baby Leaves of Broccoli (Brassica oleracea L. var. italica Plenck) and Kale (B. oleracea L. var. acephala DC.)

“…The aim of this work was to show that the morphometric traits and GLSs profile were influenced both by the climatic conditions that characterized different plant growth stages and by the genotype taken into consideration [40,41]. In any case, further studies would be needed to better define the relationship between environmental conditions and GLSs profile.…”

Strategic Successive Harvesting of Rocket and Spinach Baby Leaves Enhanced Their Quality and Production Efficiency

“…It is expected that plants from both tanks will have similar sweetness. Bell et al [32] reported that consumers preferred rocket leaves from the first cut compared to leaves from successive cuts, and the result was associated with higher glucosinolate concentrations which increased the bitterness and peppery perceptions. Fallovo et al [12] observed that reduced sugar content was associated with increased nitrate content which was not evident in our case.…”

Advanced Research on Glucosinolates in Food Products

“…In this context, the consequences for human health are important, too. This Special Issue includes eleven research articles that cover research on the effect of pre-harvest factors on glucosinolates, their hydrolyzing enzymes, and the formation of volatile hydrolysis products [ 2 , 3 , 4 , 5 ]. Further topics include the linkage between glucosinolates and sensory aspects [ 2 , 6 , 7 ], and the effects of food preparation and follow-up reactivity [ 7 , 8 , 9 , 10 ].…”

“…This Special Issue includes eleven research articles that cover research on the effect of pre-harvest factors on glucosinolates, their hydrolyzing enzymes, and the formation of volatile hydrolysis products [ 2 , 3 , 4 , 5 ]. Further topics include the linkage between glucosinolates and sensory aspects [ 2 , 6 , 7 ], and the effects of food preparation and follow-up reactivity [ 7 , 8 , 9 , 10 ]. Finally, two articles focus on the bioavailability and functional effects of isothiocyanates for human health [ 1 , 11 ].…”

“…In another study, Chowdhury et al showed that the growth conditions in a plant factory that are optimal for the plant growth of kale can differ from the optimal conditions for higher glucosinolate contents, as glucosinolate levels decrease as temperatures and humidity levels increase, though they are positively affected by increased CO 2 levels [ 3 ]. In contrast, Bell et al revealed a positive correlation between the presence of glucosinolates and the average growth temperature of rocket ( Diplotaxis tenuifolia and Eruca sativa ), demonstrating this with multiple leaf cuts, showing how the process affected the perception of pepperiness, bitterness, and hotness, which in turn reduced consumer acceptance [ 2 ]. These findings pose a challenge for the aim to increase health-promoting isothiocyanate levels, as this could reduce consumer acceptance and thereby the consumption of these products.…”