Effect of Cultivar and Harvest Date of Kale (Brassica Oleracea L. Var. Acephala) on Content of Nitrogen Compounds
A. Korus, Z. Lisiewska
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Department of Raw Materials and Processing of Fruit and Vegetables, Faculty of Food Technology, Agricultural University of Kraków, Balicka 122, 30-149 Kraków, Poland
Pol. J. Environ. Stud. 2009;18(2):235–241
The level of total nitrogen, protein nitrogen, nitrates (NO3-) and nitrites (NO2-) was measured in the leaves of kale of the cultivars Winterbor F1, Redbor F1 and Średnio Wysoki Zielony Kędzierzawy. The investigation was carried out in two successive years, the raw material being harvested three times each year, i.e. 10, 14 and 18 weeks after planting seedlings in the field. Depending on the year of the investigation, the cultivar and the date of harvest, the content found in 100 g fresh matter of kale was: 0.54-0.74 g total nitrogen and 0.46-0.50 g protein nitrogen; in 1000 g the content of nitrates (NO3-) was 248-2810 mg and of nitrites (NO2-) 0.14-0.95 mg. In both years the highest content of total nitrogen was found in leaves of Średnio Wysoki Zielony Kędzierzawy and of protein nitrogen in Winterbor F1. The cultivar Redbor F1 was characterized by the highest content of nitrates and nitrites. Comparing material from the three harvest dates, average values for the year and cultivar showed that the second harvest contained 9% more total nitrogen and 4% more protein nitrogen than the first, while the third harvest contained, respectively, 17% and 8% more than the first. Nitrate content fell by 67% and 83%, respectively, and nitrite increased by 5% (but later was reduced by 46%). Nitrate and nitrite are regulated in spinach and lettuce and for this reason understanding the accumulation of these compounds is critical if regulations are developed for kale.