The effect of freezing and thawing on the magnetic resonance imaging parameters of water in beef, lamb and pork meat

A new multisample magnetic resonance imaging (MRI) technique has been used to measure the values of T-1, T-2, magnetization transfer (MRI) rate and liquid proton density ratio (M-0%) for water in fresh and frozen-thawed beef, lamb and pork; four samples from the longissimus dorsi muscle of 25 different individuals per species were studied. The effect of two different chilling regimes, standard and tenderloin, were also studied. Standard chilled pork and lamb had a significantly higher M-0% than tenderloin chilled samples, but there was no correlation between M-0% and fresh weight; the differences in M-0% are thought to be due to differences in MR (magnetic resonance)-visible water. There was a significant decrease in water content, T-1 relaxation time, and a significant increase in MT rate in the frozen-thawed samples when all the data were pooled for each species. However, individual animals differed in the magnitude and direction of the change; this means that because of interanimal variation, measurements of MR parameters from a single sample of meat cannot be used at present to authenticate it.