Characterizing parameters of Chocolate.

The protein nitrogen and the metallic components were evaluated to characterize chocolate. Ten marks with a percentage of cocoa generally in the range 70 – 100% were analyzed. Only one was 50%. In one case the declared origin of cocoa was Venezuela. The protein nitrogen was determined by applying the Kjeldhal procedure. The percentage of the product (i.e. % of cocoa) per protein nitrogen was in the range 0.7 – 1.2, except, as expected, for the sample with 50%. In this case the percentage was 0.33. As some cations are toxic and others can have nutritional or toxic effect depending on their concentration, total arsenic, cadmium(II), lead(II), copper(II), zinc(II) and total selenium were determined. To eliminate the organic components, weighed samples of chocolate of different firms were ignited at 900°C to obtain ashes at constant weight. The range of the percentages of ashes was within 1.4 and 3.7%. Ashes were dissolved in HCl and the content of the above cations was determined by means of Atomic Adsorption (AA) spectrometry. Cadmium(II), copper(II) and lead(II) were determined in flame acetylene – air (or in furnace on the basis of the concentration), whereas total arsenic, total selenium and mercur (II) were determined by using the hydride kit and treating the samples with sodium bore hydride and 10% HCl. Concerning the cation concentration, it was observed that cadmium(II) and lead(II) are present at level less than 1 ppm (mg/kg) and then their analysis had to be carried out by using the graphite furnace. The concentration of zinc(II) and copper(II) was more than 5 ppm, often it reached 30 ppm. Zinc(II) was often double than copper(II). Copper was in the range 6 – 18 ppm, whereas zinc (II) was in the range 15 – 30 ppm. Cations analyzed by the hydride kit were present in very different amounts, but in the range of ppb (μg/kg) quantities. Mercury is present generally at about 1 ppb, except for one sample where was about 4 ppb. Higher values can be observed for arsenic present in the range within 7 – 31 ppb. The selenium concentration showed a large variability, because it was present within 3 and 50 ppb. Only one sample contains 100 ppb of selenium. It means that a range of about 100 ppb is covered. By taking in account that the cocoa percentage are different for the analyzed samples, the found quantities of arsenic can be considered near. However, such quantities are higher than the generally accepted value, about 0,2 ppb. The values relative to selenium are acceptable, even advantageous for the alimentary diet. Only one sample containing 100 ppb of selenium can be dangerous. It seems interesting to observe that the same chocolate sample with 100 ppb of selenium, contains high quantities also of the other cations, so that it can be considered the worst sample