Boiled or not boiled? - D-aspartic acid in bone proteins as proof of a burial "more teutonico"?

Around the 12th/thirteenth century, a burial method called "more teutonico" was used for the remains of high-ranking individuals who had died far from their homeland and had to be brought back for burial. Before transportation, the bodies or body parts were boiled (macerated) to remove all soft tissue. The question of whether a body was boiled postmortem, is of particular interest for historians (burial "more teutonico"?) and this question may also be relevant in a forensic context, even if only in rare cases. In 1989, Bada, Herrmann, Payan and Man ("Amino acid razemization in bone and the boiling of Emperor Lothar I." in Applied Geochemistry) suggested using the D-aspartic acid content of bone as an objective indicator of a postmortem exposure to heat. This approach was never substantiated by further studies, and more recent findings call the concept into question.Therefore, we tested the "Bada approach" by analysing the D-aspartic acid content in boiled bone samples (pig, human) using different "boiling recipes" of procedures "more teutonico" (using water, wine, or vinegar as boiling media), and discussed it under consideration of the recent literature. Using the boiled human bone samples, we also investigated whether the question of "boiled or not boiled?" could be answered by another parameter, namely by analysing the pentosidine content of a sample.An accumulation of D-aspartic acid was observed during boiling in both pig and human bone samples. It was considerably lower in the human samples and significantly influenced by the medium used. By contrast, boiling did not result in pentosidine accumulation.These experimental results call into question the reliability of the "Bada approach" - not least because the type of boiling medium may not be recreated in each individual case. Moreover, this approach does not take the current knowledge on the intravital accumulation of D-aspartic acid in bone samples of different origins into account, nor the influence of postmortem conditions on the D-aspartic acid content in non-heated samples (used as controls by Bada et al.). Overall, the approach of Bada et al. should not be accepted uncritically, as proving a treatment "more teutonico" based solely on the D-aspartic acid content seems hardly possible - and if so, only under very strict conditions. The analysis of pentosidine is not suitable for demonstrating a burial "more teutonico".