2018 ASHS Annual Conference

Many research have shown glucosinolate (GS) loss during cooking process in broccoli. While methyl jasmonate (MeJA) application significantly increases potential health-promoting GS) in broccoli (Brassica oleracea var. Italica) by mimicking insect damage, limited research looked at on how MeJA application affects GS retention after cooking. To fully utilize MeJA application, we aimed to measure how MeJA application affects GS retention after cooking. In this study, 250 µM MeJA was applied to ‘Green Magic’ broccoli four days before the harvest and we measured GS in broccoli, GS in cooking water, electrical conductance, and primary metabolites to evaluate the phytochemical profile change after three different cooking methods (boiling, steaming, and microwaving) and two cooking times (2 and 5 minutes) on control and MeJA-treated broccoli. In raw broccoli, MeJA treatment significantly (P<0.05) induced progoitrin (19%) and glucoerucin (43%), glucobrassicin (52%), neoglucobrassicin (488%), and 4-methoxy-glucobrassicin (21%) compare to the control. Among six cooking treatments (methods x times), 5 minutes boiling led to the most significant loss in total aliphatic (22%) and indole GS loss (62%) in control while it caused 47% total aliphatic and 54% indole GS loss in MeJA-treated broccoli. Even though GS loss rate were high in both control and MeJA-treated broccoli, only 5 minutes boiling cooking water from control broccoli consistently contained highest amount of glucoraphanin (0.04 µmole/g DW), total aliphatic GS (0.06 µmole/g DW), neoglucobrassicin (0.18 µmole/g DW), and total indole GS (0.2 µmole/g DW) at P<0.05; however, no significant difference was detected in MeJA-treated broccoli cooking water regardless of cooking treatments. In addition, the highest electrical conductance (EC) value was observed in control boiling 5 minutes cooking water and then MeJA 5 minutes boiling water, followed by steaming water and then microwaving water. This indicated the higher cell membrane leakage in the boiling treatment was observed in control and MeJA-treated broccoli. Sucrose, fructose, glucose, proline, isoleucine, valine, serine, oxoproline, and glutamic acid were significantly reduced in MeJA treated raw broccoli compared to control. In cooked broccoli serine was the most discriminating metabolites among all treatments, and only microwaving did not lose serine during cooking. In control cooked broccoli, sucrose was the most significantly different biomarker from partial least squares discriminant analysis while fructose was the most important biomarker in MeJA-treated broccoli. Our results suggested MeJA application on broccoli can potentially retain higher GS to provide improved phytochemicals in broccoli after cooking.