Seasonal variation of fatty acid profiles from textiles associated with decomposing pig remains in a temperate Australian environment

Abstract

A methodology to examine the human post-mortem decomposition process has been developed through the monitoring of chemical changes to decomposition fluids absorbed by clothing. Model surface deposition using clothed pigs were established during summer and winter seasons in a temperate region of Australia. Three clothing materials were investigated: cotton, polyester and cotton-polyester. Lipid decomposition products were extracted from the textiles and the fatty acid composition measured as a function of surface deposition time using gas chromatographymass spectrometry (GC-MS). Two derivatisation methods for the fatty acids were compared to establish the most effective approach and it was established that a trimethylsilylation derivatisation method is the optimal preparation technique. The summer trials revealed two rates of transformation of fatty acids from unsaturated to saturated forms, with a faster rate of change occurring earlier in the trials. A different pattern of behaviour was observed for the fatty acids detected during the winter trial, with a decrease in saturated fatty acids initially observed, followed by the conversion of unsaturated to saturated fatty acids until the end of trial. The initial change observed during the winter trial was attributed to a dehydrogenation process caused by microbiological enzymatic activity. The study has demonstrated the feasibility of examining lipid decomposition products collected in clothing from surface depositions to provide insight into the conditions and length of deposition.

Gravesoil derived postmortem interval using attenuated total reflectance-Fourier transform infrared spectroscopy and the influence of carrion-associated fabric.

“…This latter finding was consistent with the initial signs of cotton degradation reported to establish 149 to 269 days in situ deposition or burial (4) degradation when buried independently, in their highly amorphous, hydrophilic, and absorbent nature (22). On the other hand, preserved to a degree when in contact with cadaveric fluids as reported with porcine-associated cellulosic grave materials (5,6). Buried viscose spectra behaved similarly to buried cotton losing intensity at 3321 cm -1 , 2900 cm -1 , O-H and C-H stretching cellulose vibrations respectively (Figure 2).…”

“…Establishing the time elapsed for unattended death scenes is crucial for investigators to formulate a timeline of events that facilitates identification of the victim, possible suspects and corroboration of witness statements and alibis. Alongside tracking visual deterioration of the grave-associated textiles, anatomical accumulation and composition of decomposition fluids into cadaver clothing also assists in PMI estimation (5)(6)(7). During the active-bloat and purge stages, the carrion begins to release lipid-, protein-and carbohydrate-rich by-products of the degradation processes (8).…”

Comparative Decomposition of Humans and Pigs: Soil Biogeochemistry, Microbial Activity and Metabolomic Profiles

“…The large larval masses feeding on the donors in the summer may also have contributed to elevated protease activities, as these larvae are known to secrete proteases ( Pinilla et al, 2013 ). Other decomposition studies have reported seasonal differences in decomposition processes, for example, different microbial community compositions ( Breton et al, 2016 ), number and abundance of volatile organic compounds produced ( Forbes et al, 2014 ) and differential transformation of fatty acids in decomposition fluid ( Ueland et al, 2018 ).…”