Nitrate content in fruits and vegetables from commercial chains in Bulgaria

The aim of this monitoring is to evaluate the nitrate content in vegetables and fruits from the commercial chain in Bulgaria. The vegetables were purchased from the food chains in June and July. The measurements of NO3- ions were carried out with a Greentest appliance, Model ECO 5. Four samples from the conducted monitoring were with higher NO3- amount that is allowed for trade and accepted as healthy (potato, radish, and strawberries). The content of NO3- in fresh potato were 645 mg/kg at the accepted safety level 250 mg/kg. The level of nitrates also was higher in the both samples of radish 3700 mg/kg and 2934 mg/kg at accepted level as safety for consumption 1500 mg/kg. This small survey suggests that on the market in the country are still in the trade food products with not enough good quality.


INTRODUCTION
Nitrates as most of the other inorganic substances are relatively toxic and the health effect depended mostly of the amount that is digested. The content of NO 3 is an important quality characteristic of vegetables, because they constitute the major source that formed daily dietary intake from 300 to 940 mg/g [1], more than 80% of dietary nitrates consumption [2], [3], and [4]. Nonetheless, of restrictions and regulations accepted to control and minimize nitrate intake from human food, there are still vegetables on the EU market with exceeded levels. The assessment of human population nitrate exposure in Italy confirm that the acceptable daily intake was higher than the settled limits of 3.7 mg/ kg bw per day and that the ingestion of nitrates from vegetables mainly generate the highest exposure to people of all ages [5]. The current study aims to evaluate the nitrate content in the vegetables and fruits from the commercial chain in BG during summer season.

METHODS
The vegetables were purchased from the food chains in June and July. The measurements of NO 3 ions were carried out with a Greentest appliance, Model ECO 5, for measuring the level of nitrates in fresh fruits and vegetables, as well as harmful substances contained in meat and fish. The appliance is certified and calibrated based on more than 1,000 studies of leading labs using spectrometric equipment. It has certificates: SGS, CCIC-SET, EMC, LVD, and SQC. Min/max amount of measured nitrate concentration: 0-9999 mg/ kg, with permissible error: <10%.

EXPERIMENTAL
All samples were vegetables and fruits bought from the food chain supermarkets in BG, but not all of them were with clarified origin, nevertheless all of them had permission to be sell in EU market. The strawberries (2) sample was from Bulgaria, Plovdiv. The radish (1) sample was from Italy. All measurements were repeated ten times per sample, processed with Excel using ANOVA one tail, and standard descriptive analysis. The averaged values with variables, minimum and maximum in a single sample are represented in the results.

RESULTS AND DISCUSSION
The investigation is part of the research project with the goal to evaluate and screen the quality of the food from BG market. In order to assess the nitrate content of vegetables in the BG market, the random monitoring was conducted several times in different seasons. The results from the assay conducted June and July are represented in the Table 1. Vegetables with high contend of nitrates belong to families that accumulate nitrates as Brassicaceae (rocket, radish, mustard), Chenopodiaceae (beetroot, Swiss chard, spinach) and Amarantaceae; and also Asteraceae (lettuce) and Apiaceae (celery, parsley) known as species with high nitrate contents [1]. For the assessment were chosen vegetables from different classes according to the nitrate content and groups that are listed above. Four samples from the conducted monitoring were with higher NO 3 amount that is recommended (Table 1, Figures 1 and 2).   (Table 2). In some countries are set limits to maximum levels of nitrate for trade of some vegetables (beetroot, cabbage, carrot, celery, endive, Lamb's lettuce, potato, radish and rocket) which form the main source of total dietary exposure of nitrate [1]. For example, for potato in Germany the content should be less than 200 mg/kg fresh matter (fm), while in Poland there is a maximum limit of 183 mg/kg fm. In that study the content of NO 3 in fresh potato were 645 mg/kg at the accepted safety level 250 mg/kg (Figure1). The level of nitrate in radish was higher in the both samples (Table 1), 3700 mg/kg and 2934 mg/kg at accepted as safety level for consumption 1500 mg/kg (Figure 2). The reduction of nitrates in the radish sample was insignificant about 153 mg/kg, after holding in water and splashed few times for 24 hours. The reduction of dietary nitrate consumption is a desirable preventive measure of potential long-term human health risks, and that will rise the benefit of fruit and vegetable digestion [1]. Hence, with applying good practices for agriculture cultivation and with the increasing of the control and monitoring programmes that can be handle and done in the future.

CONCLUSIONS
The obtained results undoubtedly confirm that on the food chain market in BG are still in the trade food products with not enough good quality, besides of the monitoring inspections and the tidy control that exist. The Greentest appliance, Model ECO 5 give possibility to check the nitrate content in very easy and quickly manner that allow to screen and obtain reliable big data for short time.
The programmes for monitoring and control should be inevitable part of that contest for better and healthy food, as well as spreading the results from effective good agriculture practices.