Comparative evaluation of bioactive compounds in lyophilized and tray-dried rocket (Eruca sativa)

Cruciferous species such as Eruca sativa (rocket) are known to contain a variety of bioactive compounds. Total flavonoid assay showed significantly different concentrations between the lyophilized rocket (LR) (3.290.15 g/100 g) and tray-dried rocket (TDR) samples (2.42 +/- 0.22 g/100 g) measured as quercetin equivalents (QE) although the total phenolic content between the samples showed no statistical difference: 8.67 +/- 0.6 g/100g QE and 8.5 +/- 0.8 g/100g QE, for LR and TDR, respectively. The antioxidant activity, measured using the DPPH center dot assay indicated a similar scavenging activity for LR and TDR. Moreover, total isothiocyanate contents showed a two-fold higher concentration in the TDR sample (6.05 +/- 0.83 g/g) versus LR (3.26 +/- 0.59 g/g). ESI/qTOF/LC/MS analysis indicated the presence of glycosides in the LR sample and aglycones in the TDR sample. Images from Scanning Electron Microscopy revealed variations in the average particle diameter in TDR and LR particles. Practical applicationsThe comparison of two different pre-processing methods (lyophilization and tray-drying) to determine the fate of bioactive compounds such as flavonoids and isothiocyanates in arugula will facilitate the production of large batches of powder efficiently. The dehydrated powder may be used as a functional ingredient in a wide array of food products to provide enhanced nutritional benefits and good shelf life as well as reducing vegetable waste and energy consumption.