Justifying the need to prescribe limits for toxic metal contaminants in food-grade silver foils

Abstract

The use of silver foils in various food preparations is a common practice in Middle Eastern and South East Asian countries. The FAO/WHO Joint Expert Committee on Food Additives (JECFA) has included silver in the list of food additives, but specifications were not prepared. Indian food legislation has included food-grade silver foil and laid down a purity requirement of 99.9%. This leaves an unspecified margin of 0.1% or 1000 µg g⁻¹ for contaminants. Therefore, a study to investigate the levels of metallic contaminants in food-grade silver foil was undertaken. Of 178 foils analysed, 161 (90%) contained silver, whilst 10% were fraudulently made up of aluminium. In the case of silver foils, 46% of the samples adhered to the desired purity requirement of 99.9%, while 54% had a lower silver content. Copper was present in 86.3% of the silver foils, while chromium, nickel and lead contamination was found in over 54% of samples. Cadmium levels were detected in 28% of the silver foils and manganese was present in 6.8% of samples. In silver foils showing metal contaminants, average levels were found for nickel (487 µg g⁻¹), lead (301 µg g⁻¹), copper (324 µg g⁻¹), chromium (83 µg g⁻¹), cadmium (97 µg g⁻¹) and manganese (43 µg g⁻¹), which being appreciable justify the need to prescribe limits for some metals in food-grade silver foil as well as for silver powder used in confectioneries and medicinal preparations. The work reported here should encourage manufacturers to use high-purity raw materials and take suitable precautions to reduce unwarranted exposure of consumers to toxic metal contaminants.

Keywords:

• Silver foils/leafs
• food grade
• metal contaminants
• aluminium foils/leafs

Acknowledgements

The authors are grateful to the Director, ITRC, for his keen interest in the study. Thanks are due to Dr R. C. Murthy, Shri G. S. Tandon and Ms Poonam Saxena for technical discussions and assistance. S. K. K. is thankful to the Indian Council of Medical Research, New Delhi, for the award of Emeritus Medical Scientist. The manuscript is ITRC communication # 2389.