Nitrite levels in vegetables may increase during post-harvest
storage by the action of indigenous bacteria and/or the presence
of nitrate reductase (Hunt, 1994), especially when they are left at
room temperature or higher. This may explain the small amount
of nitrite (20 mg/kg) present in Gai choy during the preparation
at room temperature (Table 1). Likewise, it was demonstrated that
there was no detectable nitrite in 94% of edible fresh retail vegetables
(Hunt & Turner, 1994).