Using accumulated degree-days to estimate postmortem interval from the DNA yield of porcine skeletal muscle.

Determining the age of meat may require DNA extraction from tissue that may be frozen, chilled or sold over the counter of butchers. Until now, there has no systematic study on the ageing of meat. In the human application, the parallel is the determination of the time of death or postmortem interval (PMI). The purpose of this study was to investigate the effect of accumulated degree-days on the DNA yield of skeletal muscle and its possible application to estimate PMI. This study focused on the exposure of skeletal muscle tissue to a coastal environment. Two specimens of Sus domesticus, each weighing approximately 45 kg, were placed above ground to decompose over time. One pig was sampled over the summer season (December to February) and the other specimen during the winter season (June to August). Both the summer and winter pig studies were conducted in Drummond Cove, on the Mid West coast of Western Australia. Samples of muscle were collected at 2 day intervals for the summer and winter pigs. The daily maximum and minimum environmental temperature and humidity was recorded. Although time is an important factor in the degradation of DNA it is not critical. This study confirms that DNA degradation is best modelled as dependent on accumulated temperature rather than just time. The sequential nature and an initial decrease in the DNA yield in skeletal muscle has the potential to apply to estimation of PMI but further tests need to be conducted to confirm our findings.