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Schwermetalle in Lebensmitteln. Ueber den Zinkgehalt in Rohkakao, Kakao-Halb- und Fertigprodukten

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Altogether 52 samples of cocoa beans from 20 different origins and 40 samples of commercial chocolate tablets, chocolates, cocoa powders and instant powders were examined for their zinc content. The determinations were carried out with the aid of a flame-ASS after wet ashing in an autoclave with teflon liner. The zinc content of full cream milk chocolate with and without nuts was found to be 11,6 and 13,4 mg/kg respectively. Semi-bitter andbitter chocolates contain 17,2 and 23,2 mg/kg (mean values). The instant powders examined contained 10,7 mg/kg, the samples of cocoa powder 42,8 and 58,7 mgZn/kg. Chocolate and chocolate tablets with additions and fillings contained 10,0 and 9,8 mg/kg. For the purpose of evaluating the total amounts of copper and zinc it is important to establish also the amounts of Cu present since the total loading can be evaluated only on the basis of both elements. It appears from previous investigations (2,4) on copper contents of raw cocoa that the mean Cu-content amounts to 28,5 mg/kg. The mean content found in full cream milk chocolate was 5,8 mg/kg and that found in bitter chocolate 20,1 mg/kg. The copper content of cocoa powder is between 43,9 and 67,5 mg/kg. From this it can be seen that the limit values can be adhered to in finished products whose proportion of cocoa mass is very small such as in full cream milk chocolate with and without nuts, chocolates, chocolate tablets with additions and with fillings. In the case of semi-bitter and bitter chocolate and cocoa powder it will hardly be possible to keep to the limit value because of the high proportions of cocoa mass. Since, however, cocoa powder is usually employed in the manufacture of cocoa-containing beverages, fat-based coatings, cake masses and pudding mixes, cocoa is present in a diluted form. The limit value can therefore be adhered to, provided that other ingredients do not contribute to the existing zinc level. This can be clearly established when considering the zinc content of instant powders.

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