Physicochemical Characteristics and Nitrate Content in Fresh and Canned Pears Products

In recent years, an increasing interest concerning determination of nitrate levels in food products has been observed, essentially due to the potential reduction of nitrate to nitrite, which is known to cause adverse effects on human and animal health. The main goal of this study was measuring nitrate content of pear and apple derived canned products samples commercially available in Iran market in comparison on fresh fruits. Series analyses were performed with 80 canned pear samples produced at a large-scale local enterprise and purchased at recognized market and simultaneously fresh and 150 untreated samples was collected by going to the chosen areas of recognized farms in region of Fouman in Giulan province, Iran. In order to conduct a comparison between the content of nitrate in the studied samples, dry matter content was determined according to the association of office analytical chemists (AOAC). A ten gram sample of the prepared pear and apple was blended with 50ml distilled water in a home blender. The mixture was filtered and was passed through a glass 39 column fitted with a tape and filled with Activated alumina, in order to separate the color of Chlorophyll and get a transparent solution. The eluted solution by water filtered using 0.45um filter paper in order to eliminate the turbidity and get a clear solution. Nitrite concentration in pear samples was determined by spectrophotometric methods at a wavelength of 538 nm, after reducing nitrate to nitrite by using cadmium column. Nitrate content in analyzed fresh pears ranges between 63.22 – 143.76 mg/kg FW with an average of 101.743 mg/kg. The highest nitrate content was found in ‘Abkhoj’ (143.76 mg/kg) and the lowest content was in Amrud’ genotypes (63.22 mg/kg FW). For canned pear the nitrate level ranges between 166.11 – 374.02 mg/kg with an average of 266.08 mg/kg. All the nitrate values in canned food samples are higher than those for corresponding fresh fruits. The nitrate levels in pear compotes are much higher than those for corresponding fruit due to the concentration process that takes place during pear processing . It is clear that the result of our study shows a variation in the nitrate and nitrite levels in the different genotypes samples and processing products.