Tissue preservation of 16-18th Century mummies of Roccapelago (Modena, Italy): a SEM and FTIR study

Between 2009 and 2011, during restorative works at the Church of Roccapelago (province of Modena, Italy) a remote mountain village, hundreds of bodies, some of them mummified because of natural processes, were discovered in a forgotten crypt in use from the mid-16th to the 18th centuries. Mummification processes occurred unevenly, with bodies partially skeletonized and bodies only partly articulated [1]. 12 of these mummies, the most complete and representative, were studied with non-invasive methods and replaced in the crypt, set up as a museum (Fig. 1). The objects of this study are fragments of a variety of tissues taken from the mummies of the US 23 of the crypt of Roccapelago: skin pieces taken from different parts of the body, muscle, tendon, lung, bone, hair… The tissues were analyzed by means of FTIR spectroscopy applied in the transmission geometry, on samples obtained by mixing small quantities of the samples with pulverized KBr. In the IR spectrum of the investigated tissues the main absorption bands of the biological components such as proteins, lipids, nucleic acids, and carbohydrates were detected and characterized. The biochemical modifications recorded reveal a partial alteration of the ancient tissues which have been stabilized by the chemical-physical environmental conditions and preserved for hundreds of years. The whole IR spectrum of the tissues reveals traces of these “age-inhibitor” processes: 1) the water OH-stretching band (~3400 cm-1) features are indicative of the twofold role of the dehydration process, as a result of low temperatures and dry air, at the same time responsible for the protein structure modifications and determining the preservation; 2) conformational features of the proteins can be extracted by monitoring Amide I and Amide II bands (1500-1700 cm-1); 3) in the glucid specific spectral range (950-1150 cm-1), an increase was measured in the glucid/protein ratio, a spectroscopic marker for the AGE compounds formation as a consequence of the collagen binding to sugars in tissues [2]; 4) the amount of adipocere formation (2916-2849 cm-1, 1700 cm-1) was correlated with the position of the remains in the pile of the corpses. The bone diagenesis was monitored by means of the mineralization parameters. SEM measurements were carried out with the purpose of a morphological characterization of the tissues, in comparison with the modern ones. SEM images were acquired with Zeiss Supra40-high resolution apparatus using low beams energies. Mummified collagen fibers and collagen network are shown in the skin and compact bones reveal a lot of well preserved ultrastructural features such as Harvesian canals [3]. Septate hyphae and spores, characteristic of a fungal colonization were identified, as well as a lot of burrowing insects, such as Dermestidae, commonly referred to as skin beetles, which feed on dry animal and their predators, staphilinides [4]. [1] G. Gruppioni, D. Labate, L. Mercuri, V. Milani, M. Traversari, B. Vernia, 2010, Gli scavi della Chiesa di San Paolo di Roccapelago nell’Appennino modenese. La cripta con i corpi mummificati naturalmente, Pagani e Cristiani. Forme e attestazioni di religiosità del mondo antico in Emilia, X 2011: 219-245. [2] M. G. Bridelli, A. Dell’Anna, C. Stani, A. Baraldi, R. Boano and S. De Iasio, 2014, FT-IR spectroscopy and microspectroscopy of ancient Egyptian embalmed heads from the Museum of Anthropology and Ethnography of the University of Turin. Yearbook of mummy studies (Verlag Dr. Friedrich Pfeil, Munchen, Germany), Vol. 2, pp. 167-174 – ISBN 978-3-89937-163-5. [3] C. Stani, V. Erokhin, M. Traversari, R. Boano, E. Rabino Massa, M.G. Bridelli. 2014, SEM microscopy of mummified skin. Journal of Biological Research, 87:s1, 14 [4] V. Bugelli, D. Forni, L. Bassi, M. Di Paolo, D. Marra, S. Lenzi, C. Toni, M. Giusiani, R. Domenici, M. Gherardi, and S. Vanin, 2015, Forensic Entomology and the Estimation of the Minimum Time Since Death in Indoor Cases. Journal of Forensic Sciences , 60 (2): 525-531. ISSN 0022-1198