Why is it better to avoid using vegetables such as broccoli and spinach in a stock?

Answer by  cuprite (29)

Both broccoli and spinach have very strong flavors and colors that could influence the flavor or color of a dish that you would later make with the stock.

Answer by  blueballoon (190)

Broccoli is a member of the cabbage family; if used in stock, broccoli will impart an unpleasant overcooked cabbage flavor. Greens have similar sulfurous compounds, resulting in similar flavor.