Document Type : Original Articles
Authors
1 Department of Nutrition, School of Nutrition and Food Sciences, Shiraz University of Medical Sciences, Shiraz, Iran;
2 Department of Food Hygiene and Quality Control, School of Nutrition and Food Sciences, Nutrition and Food Sciences Research Center, Shiraz University of Medical Sciences, Shiraz, Iran
Abstract
Background: Spinach is one of the vegetables with a high concentration of nitrate which is affected by various processes such as cooking and refrigeration before consumption. The present study aimed to investigate the effect of home cooking method, which has not been studied before, on the level of nitrate and nitrite in spinach. The effect of refrigeration was studied, as well. Methods: After removing non-edible parts of spinach, it was cut into 4-7 cm pieces. Then, it was washed with deionized water thrice and drained. A part of raw spinach was set aside to measure the nitrate and nitrite and the other part was heated in a closed container without adding water, until almost all the water of the spinach was evaporated and then refrigerated. HPLC method was used to measure the nitrite and nitrate levels. The collected data were analyzed using Wilcoxon test by SPSS. Results: The mean concentrations of nitrate and nitrite in the raw spinach were 336.54±182.2 and 26.49±10.07 mg/kg, respectively. Cooking process caused a significant increase in the level of nitrate, while refrigeration process led to a significant decrease in this regard. Besides, a slight reduction was observed in the nitrite level after cooking, but the change was not statistically significant. Refrigeration also had no significant effects on the nitrite level of spinach. Conclusion: Considering the non-significant changes in nitrite levels, it seems that home cooking without adding water, unlike refrigeration, is not a proper method to reduce the intake of nitrates and nitrites from spinach.
Keywords
- World Health Organization. Chemical fact sheets
- [internet]. In Guidelines for drinking-water quality,
- Volume 1: Recommendations. Third edition; 2008.
- p. 398-400. Available from: http://www.who.int/
- water_sanitation_health/dwq/gdwq3rev/en
- Machha A, Schechter AN. Dietary nitrite and nitrate:
- a review of potential mechanisms of cardiovascular
- benefits. Eur J Nutr 2011; 50(5): 293-303.
- Katan MB. Nitrate in foods: harmful or healthy?. The
- American Journal of Clinical Nutrition 2009; 90(1):
- -12.
- Yan PM, Xue WT, Tan SS, Zhang H, Chang XH. Effect
- of inoculating lactic acid bacteria starter cultures on
- the nitrite concentration of fermenting Chinese paocai.
- Food Control 2008; 19(1): 50-5.
- Sobhan Ardakani S, Shayesteh K, Afyouni M, Mahbobi
- Soufiani N. Nitrate Concentration in Some Plants in
- Isfahan. Journal of Environmental Studies 2005; 31(37): 69-76.
- Najafi N, Parsazadeh M. Effect of Nitrogen Form and
- pH of Nutrient Solution on the Shoot Concentration
- of Phosphorus, Nitrate, and Nitrogen of Spinach in
- Hydroponic Culture. ejgcst 2010; 1(1): 41-56.
- Sobko T, Marcus C, Govoni M, Kamiya S: Dietary
- nitrate in Japanese traditional foods lowers diastolic
- blood pressure in healthy volunteers. Nitric Oxide
- ; 22(2): 136-40.
- World Health Organization. Nitrate and nitrite in
- drinking-water, Background document for development
- of WHO Guidelines for Drinking-water Quality
- [internet]. Geneva; 2011. Available from: http://www.
- who.int/water_sanitation_health/dwq/chemicals/
- nitratenitrite2ndadd.pdf
- Wolff IA, Wasserman AE. Nitrates, nitrites and
- nitrosamines. Extensive research is needed to establish
- how great a food hazard these nitrogenous substances
- present. Science 1972; 177: 15-19.
- Hord NG, Tang Y, Bryan NS. Food sources of nitrates
- and nitrites: the physiologic context for potential health
- benefits. Am J Clin Nutr 2009; 90(1): 1-10.
- Food Standards Agency. 2004 UK Monitoring
- Programme for Nitrate in Lettuce and Spinach. Food
- Survey Information Sheet 74/05 [internet]. London;
- Available from: http://www.food.gov.uk/science/
- surveillance
- Tamme T, Reinik M, Roasto M, Juhkam K, Tenno
- T, Kiis A. Nitrates and nitrites in vegetables and
- vegetable-based products and their intakes by Estonian
- population. Food Additives and Contaminants 2006;
- (4): 355-61.
- Shahbazzadegan S, Hashemimajd K, Shahbazi B.
- Determination of Nitrate Concentration of Consumed
- Vegetables and Fruits in Ardabil. Journal of Ardabil
- University of Medical Sciences 1398; 10(1): 38-47.
- Hsu J, Arcot J, Lee NA. Nitrate and nitrite quantification
- from cured meat and vegetables and their estimated
- dietary intake in Australians. Food Chemistry 2009;
- : 334-9.
- Jaworska G. Nitrates, nitrites, and oxalates in products
- of spinach and New Zealand spinach Effect of
- technological measures and storage time on the level
- of nitrates, nitrites, and oxalates in frozen and canned
- products of spinach and New Zealand spinach. Food
- Chemistry 2005; 93: 395-401.
- Prasad S, Chetty AA. Nitrate-N determination in leafy
- vegetables: Study of the effects of cooking and freezing.
- Food Chemistry 2008; 106(2):772-80.
- Huarte-Mendicoa JC, Astiasaran I, Bello J. Nitrate
- and nitrite levels in fresh and frozen broccoli. Effect
- of freezing and cooking. Food Chemistry 1997;
- (1-2):39â42.
- Nabrzyski M, Gajewska R. The content of nitrates and
- nitrites in fruits, vegetables and other foodstuffs. Rocz
- Panstw Zakl Hig 1994; 45(3): 167-80.
- Abo Bakr TM, El-Iraqui SM, Huissen MH. Nitrate and Nitrite Contents of Some Fresh and Processed Egyptian
- Vegetables. Food Chemistry 1986; 19: 265-75.
- Chung JC, Chou SS and Hwang DF. Changes in nitrate
- and nitrite content of four vegetables during storage at
- refrigerated and ambient temperatures. Food Additives
- and Contaminants 2004; 21(4): 317-22.
- Chew SC, Yang Bao KNP, Ismail A. Changes in nitrate
- and nitrite levels of blanched amaranthus during
- refrigeration storage. Journal Sains Kesihatan Malaysia
- ; 9(1): 29-34.
- Pirsaheb M, Rahimian S, Pasdar Y. Nitrite and Nitrate
- content of fruits and vegetables in Kermanshah (2010).
- Journal of Kermansha University of Medical Sciences
- ; 16(1): 76-83.
- Joint FAO/WHO Expert Committee on Food Additives
- [Internet]. Available from: http://apps.who.int/ipsc/
- database/evaluations/chemical.aspx?chemID=711
- Chou SS, Chung JC and Hwang DF. A High Performance
- Liquid Chromatography Method for Determining
- Nitrate and Nitrite Levels in Vegetables. Journal of
- Food and Drug Analysis 2003; 11(3): 233-8.
- Bednar CM, Kies C, Carlson M. Nitrate-Nitrite levels in
- commercially processed and home processed beets and
- spinach. Plant Foods for Human Nutrition 1991; 41: 261-8.
- Gajda J, KarÅowski K. The content of nitrates in
- vegetables and potatoes in 1987â1991. Roczniki Pan´
- stwowego ZakÅadu Higieny 1993; 44(4): 301-7.
- Petersen A, Stoltze S. Nitrate and nitrite in vegetables
- on the Danish market: content and intake. Food
- Additives and Contaminants 1999; 16(7): 291-9.
- Dennis M, Wilson LA. Nitrates and Nitrites. In
- Encyclopedia of Food Sciences and Nutrition. Second
- Edition; 2003. p. 4136-42.
- Tamme T, Reinik M, Püssa T, Roasto M, Meremäe K,
- Kiis A. Dynamics of nitrate and nitrite content during
- storage of home-made and small-scale industrially
- produced raw vegetable juices and their dietary intake.
- Food Addit Contam Part A Chem Anal Control Expo
- Risk Assess 2010; 27(4): 487-95.
- Iammarino M, Taranto AD, Cristino M. Endogenous
- levels of nitrites and nitrates in wide consumption
- foodstuffs: Results of five years of official controls
- and monitoring. Food Chemistry 2013; 140:763-71.
- Hunt J, Turner MK. A survey of nitrite concentrations in
- retail fresh vegetables. Food Additives & Contaminants
- ; 11(3): 327-32.
- Leszczynska T, Filipiak-Florkiewicz A, Cieslik
- E, Sikora E, Pisulewski PM. Effects of some
- processing methods on nitrate and nitrite changes in
- cruciferousvege tables. Journal of Food Composition
- and Analysis 2009; 22: 315-21.
- Bosch NB, Mata MG, Pefiuela MJ, Ruiz Galfin T, Lopez
- Ruiz B. Determination of nitrite levels in refrigerated
- and frozenspinach by ion chromatograph. Journal of
- Chromatography A 1995; 706: 221-8.
- Ferreira LC, Cataneo AC. Nitric oxide in plants: a brief
- discussion on this multifunctional molecule. Scientia
- Agricola 2010; 67(2): 236-43.
- Spoelstra SF. Nitrate in silage. Grass and Forage
- Science 1985; 40: l-11.