NITRATE, NITRITE, CALCIUM, POTASSIUM AND SODIUM IN ORGANIC, HYDROPONIC AND CONVENTIONAL VEGETABLES

Abstract

Lettuce and arugula are vegetables that provide several health benefits and represent  the  most  produced  and  consumed  leaf  vegetables  in  Brazil.  The present study aimed to assess the levels of nitrate, nitrite, potassium, sodium and calcium in lettuce and arugula grown using organic, hydroponic and conventional systems. Nine samples of each vegetable grown using the three systems were used. The vegetables were harvested from properties in the municipalities of Vale do Taquari, Rio Grande do Sul, Brazil. The data were analyzed using the Kruskal-Wallis  non-parametric  test  with  a  significance  threshold  set  at  5%  (p≤0.05). Vegetables obtained from the hydroponic system showed higher mean levels of nitrate (p≤0.05) compared with organic and conventional vegetables; organic arugula was the only one that presented nitrite in its composition (3.52±4.92 mg/kg). Arugula and lettuce showed the highest mean levels of potassium when grown using the organic system (270.86±61.92 mg/100 g and 207.45±46.53 mg/100 g, respectively). Organic and hydroponic arugula exhibited the highest mean levels of calcium, whereas samples of conventional lettuce presented the highest mean level of calcium (28.53±7.20 mg/100 g). Organic lettuce and arugula were the ones with the highest concentrations of sodium (4.67±2.65 mg/100 g and 3.02±1.26  mg/100 g,  respectively).  It is concluded that the hydroponic  vegetables  exhibited  significantly  higher  mean  levels  of  nitrate. Except for calcium in lettuce samples and sodium in arugula samples, we found greater amount of minerals in organic vegetables.