Proteomic analysis of experimental foodcrusts reveals discrepancies between food input and recovered protein signal

In order to investigate how representative the recoverable proteins from charred organic residues (foodcrust) are of the food mixture cooked to produce them, a protein-rich (salmon), lipid-rich (beef fat) and carbohydrate-rich (beetroot) food were mixed, cooked and analysed. The three ingredients were mixed in 20% increments, resulting in 21 different mixtures covering all combinations of the three foodstuffs. The mixtures were placed in ceramic vessels and heated nine times with samples taken after the first, fifth and ninth heating event. Then the vessels with foodcrust were buried for 52 days and sampled again after excavation. The extracted proteins indicate substantial disparities in the relative abundance of an ingredient in the food mixture and the percentage of identified proteins it contributed. In particular salmon proteins seem overrepresented in the recovered proteome, followed by beef fat and lastly beetroot. Additionally, we found that only a limited number of proteins could be identified after the burial and that only salmon and beetroot contributed to the after burial proteomes.