Effect of harvesting time at morning, afternoon, and evening on nitrate and nitrite level in spinach (Amaranthus tricolor L.) and mustard (Brassica rapa L.)

Abstract

Objective: The objective of this study is to determine the effect of harvesting time at morning, afternoon, and evening on nitrate and nitrite level in spinach and mustard. Methods: Nitrite identification was done using sulfanilic acid reagent and N-(1-naphthyl) ethylenediamine dihydrochloride. Identification of nitrate was done using reagent ferrous sulfate. Determination of nitrites level was performed visible spectrophotometry using N-(1-naphthyl) ethylenediamine dihydrochloride at maximum wavelength of 540 nm. Nitrate determination is taken with the same method but started with reduction process from nitrate into nitrite using Zn powder in acid condition and then measured as nitrite. Results: Research result shows that there is a change of nitrate and nitrite level from the spinach harvested at morning, afternoon, and evening. Conclusion: Spinach and mustard are better harvested in the morning because it contains nitrite less than in spinach picked afternoon and evening. Level of nitrite increases from morning to afternoon and decreases from afternoon to evening. However, the level of nitrate decreases from morning to afternoon and increases from afternoon to evening.