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

Luke Bell,Stella Lignou,Carol Wagstaff

doi:10.3390/foods9121799

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.

Highlights

Rocket salad species such as Diplotaxis tenuifolia and Eruca sativa are leafy vegetables of the order Brassicales, and are popular throughout the world [1]
Previous studies have evaluated sensory properties of rocket leaves [3,4,5,6,7,8] in conjunction with phytochemical compositions, and in one instance, consumer preferences according to human taste receptor genotype [9]
The majority of rocket supplied to the UK market is D. tenuifolia, with E. sativa making up a small amount

Summary

Introduction

Rocket ( known as arugula and rucola) salad species such as Diplotaxis tenuifolia and Eruca sativa are leafy vegetables of the order Brassicales, and are popular throughout the world [1]. They are commonly sold in bags of loose leaves, or as part of a leafy salad mixture with other crops, such as lettuce, spinach, and watercress [2]. One factor not accounted for in any of these studies is the temporal variability of rocket produce over the course of a growing season, and the inherent environmental variability associated with this.

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Results

Conclusion