Content of nitrates, nitrites, and oxalates in New Zealand spinach

The levels of nitrates, nitrites, and oxalates were evaluated in usable parts of New Zealand spinach destined for consumption and technological processing. In a two-year investigation, plants with stems up to 15 cm in length, grown from sowing, were obtained in seven harvests and from seedlings in eight harvests. The New Zealand spinach contained in fresh matter, 449-2804 mg NO3-/kg, 0.09-0.77 mg NO2-/kg, and 506-981 mg/100 g of total oxalates; of this amount 69-98% constituted the water-soluble oxalates. In dry matter, the respective values were 9.4-47.4 g/kg, 0.9-12.1 mg/kg, and 8.8-15.4 g/100 g, respectively. The content of the discussed compounds depended on the usable parts of the plant, the year of investigation, and the time of harvest, while the method of growing did not affect the above amounts. More nitrates and nitrites were found in the stems with leaves than in leaves alone. Plants harvested in July showed the smallest content of nitrites and the greatest of nitrates, and in September the smallest contents of nitrates and oxalates, but the greatest of nitrites. (C) 2004 Elsevier Ltd. All rights reserved.