Changes in nitrate and nitrite concentrations over 24 h for sweet basil and scallions

Nitrate and nitrite concentrations were determined for sweet basil and scallions over 24 h to determine if time of sampling or harvest impacts concentrations in raw vegetables. Also, nitrate and nitrite concentrations were determined separately for various edible parts of these plants. Basil had significant changes in nitrate and nitrite concentrations over a 24 h period. Nitrate was correlated to changes in light intensity with a 3 h lag time. The highest nitrate concentrations in basil (2777 ppm) occurred around 3 h after the light intensity peaked and had low values (165–574 ppm) during the dark period. The scallion nitrate and nitrite concentrations were always low but nitrate showed a peak a few hours before sunrise. Nitrate and nitrite concentrations in some raw vegetables may be reduced by harvesting at the best time of day for each type of plant. Nitrate concentrations were different in the edible plant parts tested.