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.

Approximately 70% of the iron and zinc in wheat is contained within the aleurone cell layer. This layer is highly resistant to food processing, chewing and intestinal digestion, meaning that the bioaccessibility of iron and zinc from these cells is limited. In this proposal we will use micro-milling techniques to rupture the aleurone cell walls with the aim of increasing iron and zinc availability from wheat breads. We have already shown that micro-milling increases the solubility and absorption of iron from wheat flour in vitro.

It is possible to extract and purify aleurone from wheat flour. Our proposal therefore has 2 aims: (i) to ascertain whether micro-milling wholegrain flour increases iron and zinc availability from wholegrain bread; (ii) to determine whether addition of micro-milled purified aleurone flour to white flour increases iron and zinc availability from white bread.

We will take both an in vitro and in vivo approach to address these aims. Our in vitro studies will use a well characterised in vitro digestion protocol, together with measurements of iron and zinc uptake by Caco-2 cells (using ICP-MS). These studies will assess the effect of: (a) different hydrothermal processing methods; (b) the breakdown of phytate; (c) the incorporation of other dietary factors; on iron and zinc availability from breads made from standard milled or micro-milled wheat flour. Next we will carry our human feeding studies to assess the bioavailability of iron (measured using serum iron curves) and zinc (measured using stable isotopes) from breads manufactured from wholegrain flour or from white flour enriched with aleurone flour. Finally, in collaboration with Campden BRI, we will assess the effects of micro-milling on the structure of bread, and measure consumer acceptability of these novel bread products, using a range of quantitative sensory techniques.

The proposed project will benefit relevant stakeholders beyond the academic community, including the DRINC consortium and the wider commercial sector. Our proposal will address directly the DRINC Research Challenge "Understanding the relationship between food processing and nutrition" and will have impact on the Research Challenge "Designing foods to maintain and improve health". Furthermore, our work is also relevant to the wider BBSRC strategic priorities "Food, nutrition and health" and "Healthy ageing across the life-course".

The proposal focuses on novel food processing techniques to improve iron and zinc bioaccessibility from wheat. Iron and zinc deficiency are recognised as global health problems by the World Health Organisation. In addition, there are public health concerns in the UK regarding the levels of these essential micronutrients in the diets of a number of population groups. Cereals and cereal products are the most important sources of iron and zinc for many individuals in the UK and our multidisciplinary approach will ultimately have impact for consumers through the provision of everyday food products with enhanced iron and zinc bioavailability. There are also clear potential benefits for the food industry, e.g. in the design of novel foods with enhanced nutritional benefit, and through the utilisation of functional food ingredients (e.g. micro-milled aleurone as a bioavailable source of iron and zinc). We anticipate that our research will also have impact for policy-makers when formulating dietary advice and guidelines on iron and zinc bioavailability from cereals and cereal products.

To ensure appropriate dissemination of results for maximum impact, the applicants will have regular meetings with their collaborators to discuss research findings. In addition, we will assemble a project management team that includes external expert advisors to help guide our basic research towards industrial application. A number of the applicants have relevant experience of achieving successful knowledge exchange and commercialisation activities, particularly with the food industry, through collaborative industrial grants, patents, exploitation activities and dissemination events. We will exploit this expertise to provide maximum impact for our work.