Spectrophotometric Assessment of the Differences Between Total Nitrate/Nitrite Contents in Peel and Flesh of Cucumbers

Abstract

A spectrophotometric method based on the reduction of nitrates to nitrites was applied to the determination of the difference between total nitrate and nitrite contents in the extracts from the cucumber peel and flesh. The content of these ions was determined in glasshouse cucumbers and those grown in the open fields, both marketed in Poland. Nitrate and nitrite extraction was performed using the Griess diazotization reaction and carried out according to the ISO recommendation (ISO 6635, 1984). It was observed that the mean nitrate content in the peel was significantly higher (p < 0.0001) than the mean nitrate content in the flesh. It was also proved that cucumber peel accumulated nearly threefold higher amount of nitrates than the flesh. The nitrite concentrations in all tested samples were below the limit of quantification. Despite statistically significant differences in the nitrate contents between the peel and the flesh, no excessive levels were found. A comparison of the current results to those reported for Poland and other countries is also presented.