Freezing Broccoli Sprouts Increases Sulforaphane Yield

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Three-day old broccoli sprouts are concentrated sources of glucoraphanin, which is the precursor to sulforaphane.  Fresh broccoli sprouts contain 10 to 100 times more glucoraphanin by weight than mature broccoli plants. 1  Fresh broccoli sprouts can contain at least 73 mg of glucoraphanin (also called sulforaphane glucosinolate) per 1-oz serving.

A study from 2015 published in the journal RSC Advances by researchers from the College of Food Science and Technology, Nanjing Agricultural University, Nanjing, People’s Republic of China and the College of Food Science and Engineering, Qingdao Agricultural University, Qingdao, People’s Republic of China, investigated whether freezing broccoli sprouts would have an effect on glucoraphanin and ascorbic acid content, myrosinase activity, sulforaphane and sulforaphane nitrile formation.  2

The researchers froze broccoli sprouts at −20 °C (DF-20), −40 °C (DF-40) and −80 °C (DF-80) or stored at −20 °C (LN-20), −40 °C (LN-40) and −80 °C (LN-80) after being frozen in liquid nitrogen for 5 min or always frozen in liquid nitrogen (LN).

The results showed the following:

  • glucoraphanin content was not significantly affected by freezing
  • myrosinase activity was enhanced
  • sulforaphane yield  was increased by 1.54–2.11 fold
  • sulforaphane nitrile formation decreased
  • ascorbic acid content was decreased

By freezing fresh broccoli sprouts, sulforaphane can be increased by on average 1.825 times its original value when fresh and not frozen. 

Eating frozen broccoli sprouts may not be very appetizing.  Instead it is recommended to use the frozen broccoli sprouts in a smoothie.  Make sure you use the broccoli sprouts straight from the freezer and do not allow them to thaw.