Stability of added iodine in processed cereal foods

Abstract

The stability of iodine from iodized salt was measured in white bread, grain bread, sweet biscuits and the breakfast cereals, Weetbix® (a flaked, pressed, wheat product), Ricies® (a puffed rice product) and toasted muesli, as part of the New Zealand Government's initiatives to address the public health issue of low iodine intake by most New Zealanders. Triplicate runs of each product were manufactured by commercial food manufacturers between September 2006 and May 2007 with iodized and non-iodized salt. Triplicate samples were taken at various steps during processing of each food and analysed for moisture and iodine content. Iodine concentration was determined by inductively coupled plasma–mass spectrometry following an alkaline digestion. Iodine, at the equivalent of 25–65 mg of iodine per kg salt, was 100% retained in each of the selected foods from the time of mixing to the final product. These results imply that all iodine added via salt at the time of manufacture is available for consumption but not necessarily bioavailable. These data can be used for modelling the impact of strategies to increase iodine exposure. Salt as an ingredient is not a good predictor of iodine intake due to the inhomogeneity of iodine in iodized salt.

Keywords:

• iodine
• stability
• retention
• processed foods
• bread
• cereals
• iodized salt

Acknowledgements

This work was undertaken by the Institute of Environmental Science and Research Ltd. as part of their contractual agreement with the New Zealand Food Safety Authority. The key participation of management and technical staff at Coupland's Bakeries, Hornby, Christchurch (in particular Scott McKean) and Sanitarium, Auckland (in particular Richard Hark), is gratefully acknowledged. Thanks also to Shirley Jones, Christchurch Science Centre, for moisture analyses and sample dispatch.