Research reveals that chopping broccoli and letting it sit for 90 minutes before stir-frying helps retain significantly more sulforaphane, a compound with potential cancer-fighting properties.

In recent years, broccoli has gained widespread attention for its rich content of sulforaphane, a compound shown to help regulate blood sugar levels and possibly combat cancer. This has led to a growing market for broccoli extract supplements.

However, previous studies have indicated that consuming fresh broccoli provides a greater amount of sulforaphane compared to supplements. To explore the best cooking methods for preserving this beneficial compound, a team of researchers in China conducted a study, publishing their findings in 2018 in the Journal of Agricultural and Food Chemistry. Their conclusions, however, might challenge those short on time.

The Origin of Sulforaphane

Sulforaphane isn’t directly present in broccoli but is produced through the conversion of a class of compounds known as glucosinolates. This conversion requires an enzyme called myrosinase, which broccoli naturally contains as part of its defense mechanism against herbivores. Activating myrosinase requires some degree of physical disruption, such as chopping or chewing.

Unfortunately, common cooking methods like boiling or microwaving drastically reduce glucosinolate levels in broccoli—even after just a few minutes. Myrosinase, being highly sensitive to heat, is often destroyed during cooking. Therefore, eating raw broccoli is the best way to maximize sulforaphane intake, though this option isn’t appealing to everyone.

Can Stir-Frying Preserve Sulforaphane?

Given that stir-frying is one of the most popular cooking methods in China, the research team investigated whether this technique could better preserve sulforaphane. They observed that little research had focused specifically on how sulforaphane behaves during stir-frying.

The team purchased fresh broccoli from local markets and conducted experiments. They chopped the broccoli into fine pieces, roughly 2mm in size, to activate the myrosinase enzyme as effectively as possible. The samples were then divided into three groups: one group was eaten raw, another was stir-fried immediately after chopping for four minutes, and the third was stir-fried four minutes after letting the broccoli sit for 90 minutes.

The Effect of Letting Broccoli Sit After Chopping

The results showed that broccoli stir-fried immediately after chopping contained 2.8 times less sulforaphane than the broccoli that was allowed to sit for 90 minutes before cooking. This demonstrates that letting broccoli sit gives its enzymes enough time to convert glucosinolates into sulforaphane, significantly boosting the compound's retention.

The researchers recommend waiting around 90 minutes after chopping broccoli before cooking it to maximize sulforaphane levels. While they did not test shorter durations, they believe a 30-minute resting period might yield similar results.

This extended preparation process may deter many from trying it. The research team is exploring ways to streamline the method, but for those unwilling to wait, consuming raw broccoli remains the simplest alternative.