Increasing Micronutrient Bioavailability from Wheat
Nutritional deficiency in essential dietary metals such as iron and zinc is a public health concern in the UK, particularly for girls and young women. Approximately 30 - 50% of the iron and zinc in the UK diet is provided by cereals and cereal products (e.g. bread, breakfast cereals and baked goods). However, in wholegrain wheat, most of the iron and zinc is physically contained within a single layer of cells called the aleurone layer. Our recent work shows that aleurone cells are resistant to physical disruption and digestion as they pass along the gastrointestinal tract and are excreted intact in faeces. The aleurone layer is removed during processing of wheat into white flour and hence much of the iron and zinc is lost. While iron is added back into white flour at the milling stage, there is currently no addition of zinc. The aim of this study is to use novel food processing techniques to increase the bioavailability of the naturally-occurring iron and zinc in wheat. This process, called micro-milling, ruptures the aleurone cell walls and potentially makes the iron and zinc more available for absorption. In addition, we will use purified aleurone which has been micro-milled to enrich white flour with iron and zinc. Our recently published work shows that micro-milling increases the solubility of iron and enhances iron absorption by intestinal epithelial cells, and we expect the same to be true for zinc.
The main purpose of our proposal is to build on recently published data and further characterise iron and zinc availability from micro-milled wheat flour. We hypothesize that micro-milling will increase iron and zinc availability from wholegrain flour and from aleurone-enriched white flour. Next, we will carry out human intervention studies to assess iron and zinc bioavailability from bread rolls manufactured from micro-milled wholegrain flour or from white flour enriched with micro-milled aleurone flour. Here we hypothesize that bioavailability of both iron and zinc will be enhanced in foods containing micro-milled flour compared with standard-milled flour. Finally, we will analyse the structure of breads produced using micro-milled wheat flour and assess consumer acceptability of these products in a range of sensory tests. Our hypothesis is that micro-milling will not adversely affect food structure or consumer acceptability. We believe that our research strategy will increase the nutritional quality of food products manufactured from wholegrain wheat, and potentially have health benefits for those at risk of iron and zinc deficiency. Furthermore, our studies might identify micro-milled aleurone as a potential functional food ingredient for use in fortifying or enriching cereal-based products to increase iron and zinc content and bioavailability.