The influence of storage condition on nitrite, nitrate and vitamin C levels in vegetables

Abstract

Vegetables are the main sources of nitrate and nitrite in food. The presence of nitrate and nitrite at a high level may cause a negative impact on health, because nitrite and nitrate when reduced to nitrite, may react with alkylamine to form carcinogenic nitrosamine. The influence of temperature and time of storage on nitrite, nitrate, and vitamin C contents in vegetables were investigated in this study. The vegetables were sweet mustard, bokchoy, spinach and lettuce obtained from a local market. Samples were stored at ±25 C and ±5 C. Analysis of nitrite, nitrate, and vitamin C was conducted in fresh samples, after storage for 24 and 48 hours. Nitrite was analyzed by spectrophotometry at 540 nm. Nitrate reduced into nitrite with Zn in acidic conditions and then analyzed as nitrite. Vitamin C was analyzed by titration with 2.6-dichlorophenolindophenol. During storage, nitrite and nitrate increased, while vitamin C decreased. Nitrite and nitrate content in fresh samples were 15.22 and 22.46 mg/kg (sweet mustard), 12.57 and 6.55 mg/kg (bokchoy), 20.26 and 90.60 mg/kg (spinach), 18.77 and 32.68 mg/kg (lettuce), respectively. Vitamin C content in fresh samples was 101.15 mg/100g (mustard), 92.17 mg/100g (bokchoy), 88.95 mg/100g (spinach), 40.03 mg/100g (lettuce). After storage for 48 hours at ±25 C, nitrite and nitrate increased 44.97% and 53.19% (mustard), 46.18% and 62.59% (bokchoy), 43.86% and 16.48% (spinach), and 41.05% and 47.09% (lettuce), respectively. Vitamin C decreased 67.57% (mustard), 24.68% (bokchoy), 81.25% (spinach), and 79.74% (lettuce). Storage at ±5 C, showed that nitrite and nitrate increased 27.54% and 35.08% (mustard), 13.75% and 43.51% (bokchoy), 19.59% and 10.60% (spinach), 19.85% and 25.16% (lettuce), respectively. Vitamin C decreased 30.88% (mustard), 6.05% (bokchoy), 60.92% (spinach), and 74.94% (lettuce). During storage, nitrite and nitrate increased more significantly at ±25 C than ±5 C while vitamin levels C decreased and were more effective at 25 C than 5 C.

Analysis of Nitrosamines in Processed Meat Products in Medan City by Liquid Chromatography-Mass Spectrometry

“…The regression line equation obtained is y = 258 x + 85.82 with a correlation coefficient (r) of 0.9995. This shows a linear correlation between the area of the chromatogram and the concentration of NTCA [5], [6].…”

“…The use of nitrite in processed meat products may react with alkyl amines to form carcinogen nitrosamines. The maximum level in processed meat set by WHO WHO is 10 µg/kg [3], [4], [5], [6]. There are several factors affecting the formation of nitrosamines, namely the concentration of nitrite, acidity, temperature, storage condition, the alkalinity of amines, and the presence of catalysts or inhibitors.…”

The Effect of Boiling Time and the Type of Utensil Used on the Nitrite and Nitrate Contents in Carrots (Daucus carota L.)

“…NED solution was made by dissolving 0.350 g N-(1naphthyl) ethylenediamine dihydrochloride in 250 ml acetic acid solution 15%, filtered and stored in brown bottle. Sulfanilic acid solution was prepared by dissolving 0.850 g sulfanilic acid in 250 ml acetic solution of 15%, filtered and stored in brown bottle [11,14].…”

“…The presence of nitrite was identified with sulfanilic acid and NED solution and allowed for a little while. The presence of nitrate was tested by adding several drops ferrous sulfate solution and then few drops of concentrated sulfuric acid added slowly through the inner wall of the test tube, then the color produced was observed [14,15].…”

“…The determination of nitrate was done after reducing nitrate into nitrite and determined as nitrite [14,15]. Ten (10) ml of filtrate prepared above was transferred into a volumetric flask of 50 ml added Zinc powder (1 g) and 1 ml hydrochloride acid 0.1N, shaken and allowed to stand for 10 minutes, then 2.5 ml sulfanilic acid reagent was added and stirred to homogenous.…”