Food Proteomics: Mapping Modifications

Proteins are an essential element in the human diet. As food ingredients, they are primarily sourced from plants and animals; important sources include cereals, meat, poultry, fish and dairy. Proteomics offers a powerful new way to characterise the protein component of foods. Proteomics not only reveals which proteins are expressed in each tissue type, it also allows the investigation of differences in the protein composition of different tissues. In addition it has the power to track the proteome of tissues before and after harvest/slaughter, and to evaluate the effect of downstream treatments such as cooking or curing. The proteomic evaluation of food proteins presents a unique set of challenges and opportunities. Muscle, milk and cereal proteomes are dominated by very abundant proteins, creating a dynamic range problem. In addition to post-translational modifications produced in vivo, food proteins are subjected to a wide range of post-harvest/post-slaughter environmental and processing insults prior to consumption. These modifications include side-chain oxidation, cross-link formation and backbone cleavage, and critically influence key food properties such as shelf-life, nutritional value, digestibility and health effects. A profound understanding of proteomics, protein modifications and redox chemistry has allowed us to pioneer the application of redox proteomics to foods. This has led to the development of a unique proteomics damage scoring system, allowing a direct link between molecular-level understanding to intervention/mitigation at the processing level (Dyer et al., 2010). We anticipate that this ability will be pivotal in the development of nextgeneration food products. This chapter outlines current achievements in the field of food proteomics. It deals with the full spectrum of protein-containing foods, including dairy, meat, seafood and cereal proteins. We focus on ex vivo protein modifications and their effects on foods. We devote attention to redox proteomics approaches applied to food, and pay special attention to the recent development of advanced redox proteomic-based approaches to evaluate and track food protein modifications. These approaches are illustrated in a case study that compares the protein damage level in a number of commercially available dairy products.