Microwave cooking increases sulforaphane level in broccoli.

Yingjian Lu,Tianbao Yang,Xinyi Pang

doi:10.1002/fsn3.1493

Abstract

Sulforaphane (SFR), an anticarcinogenic compound, forms from the hydrolysis of glucoraphanin (GLR) in broccoli. Cooking methods have been shown to affect broccoli GLR and SFR levels, but little is known about the effect of lightly cooking processes on them. In this study, the effects of microwave and low‐temperature cooking on GLR and SFR contents in broccoli were investigated. Both microwaving and mild heating increased the GLR and SFR levels in broccoli compared to the raw samples (without any treatment). In particular, SFR level was significantly low under 40°C and dramatically increased from 40 to 60°C, but nothing was detected at 70°C. Compared with conventional heating, microwave heating increased the GLR and SFR yield by about 80% at 50 and 60°C. Microwave power level also influenced the SFR contents. At the same temperatures (50 and 60°C), high‐power microwave (950 W) with a short time produced over 40% more SFR than low‐power microwave treatment (475 W). Hence, mild heating by microwave could increase the GLR and SFR levels in broccoli, and high‐power microwave heating with temperature control at 60°C could retain higher bioavailability of these bioactive compounds in broccoli.

Highlights

| INTRODUCTIONBroccoli is mainly consumed and cooked by thermal treatment including boiling, steaming, and microwaving
Broccoli contains a group of secondary metabolites called glucosinolates (GSL)
Negatively correlated with temperature when it increased to 70°C. These results indicate that microwave power level plays a dominant role in influencing GLR and SFR contents of broccoli, while temperature only positively affects their levels in a certain range

Summary

| INTRODUCTION

Broccoli is mainly consumed and cooked by thermal treatment including boiling, steaming, and microwaving. These cooking processes could induce physical disruption of broccoli, leading to loss of cellular compartmentalization and mixing of GSL and MYR, which are separated from each other by vacuole membrane (Jones, Faragher, & Winkler, 2006). Despite many studies on different cooking processes in terms of the GSL contents of broccoli, little research has evaluated the effect of mild thermal treatment achieved by common domestic cooking methods on the GLR and SFR contents. This study determines the effect of temperature and power level on GLR and SFR contents in broccoli microgreens during microwave treatment and compared these two bioactive compounds in florets and stems of broccoli

| MATERIALS AND METHODS

Findings

| DISCUSSION

| CONCLUSIONS