Determination of freshness of pork by the contents of nucleic acid-related substances

"In the present study, the contents of nucleic acid-related (NAR) substances such as ATP, ADP, and Hx in pork were measured to investigate whether the freshness of pork could be estimated from these contents. Firstly, experimental pork samples were obtained from 12 crossbred (WLD) and 8 Duroc pigs after 24 hrs of slaughter. These samples were stored at 4 deg C for up to 18 days, and the changes of NARs contents were recorded during storage. The contents of ATP, ADP and AMP were approximately 0.2 micro moles/g meat throughout the preservation period. The content of IMP was highest on the first day of preservation, and then decreased gradually during subsequent preservation period, whereas those of HxR and Hx increased. To evaluate the freshness of fish, following formula has been used. K=(HxR+Hx)/(ATP+ADP+AMP+IMP+HxR+Hx)*100 In pork, however, little changes in the contents of ATP, ADP and AMP were observed. For the estimation of freshness of pork, therefore, following modified formula was established. MK=(HxR+Hx)/(IMP+HxR+Hx)*100 Highly significant positive correlation was observed between mK values and the postmortem days in the experimental pork samples. Provided pork is stored at 4 deg C, postmortem days can be estimated by formula shown below, y(day)=-0.811+0.033mk(%) +0.003mk(%) sup2 (R sup2=0.881) Secondly, imported and domestic pork samples were obtained from a supermarket, and the contents of NARs were measured. IMP contents in domestic and imported pork samples were 4.20 and 1.55 micro moles/g, respectively. HxR and Hx contents and mK values of imported pork samples were higher than domestic ones. Provided these pork samples were stored at 4 deg C during marketing process, the preservation periods of the domestic and imported samples are estimated to be 3-14 and 18-25 days, respectively."