Survey of Nitrate Ion Concentrations in Vegetables Cultivated in Plant Factories: Comparison with Open-Culture Vegetables.

A survey of nitrate-ion concentrations in plant-factory-cultured leafy vegetables was conducted. 344 samples of twenty-one varieties of raw leafy vegetables were examined using HPLC. The nitrate -ion concentrations in plant-factory-cultured leafy vegetables were found to be LOD-6,800 mg/kg. Furthermore, the average concentration values varied among different leafy vegetables. The average values for plant-factory-cultured leafy vegetables were higher than those of open-cultured leafy vegetables reported in previous studies, such as the values listed in the Standard Tables of Food Composition in Japan-2015-(Seventh revised edition). For some plant-factory-cultured leafy vegetables, such as salad spinach, the average values were above the maximum permissible levels of nitrate concentration in EC No 1258/2011; however, even when these plant-factory-cultured vegetables were routinely eaten, the intake of nitrate ions in humans did not exceed the ADI.