Influence of cooling and freezing of minced pre-rigor muscle on the breakdown of ATP and glycogen.

The high water-holding capacity of pre-rigor beef can be preserved for months by rapid freezing of the minced salted or unsalted bovine muscle before onset of the breakdown of ATP. If beef frozen in this way is processed without preceding thawing, sausages of excellent quality are obtained. The same result can be obtained using beef salted and freeze-dried in the pre-rigor state. It is important in both procedures to ensure that the depletion of ATP during freezing is kept to a minimum. The optimum conditions for cooling and freezing were therefore studied. If NaCl is not added, the rate of ATP breakdown decreases with falling temperature to about +6°C but then increases with further cooling, reaching a maximum rate at about -1°C, at which temperature the meat remains for a relatively long period during freezing. If the beef is salted, the rate of ATP hydrolysis decreases with falling temperature until the meat is frozen. Above + 3°C the concentration of ATP is lower in salted than unsalted meat in the first hours post mortem, but below this temperature the position is reversed. The influence of temperature on lactate formation, i.e. on the rate of glycolysis in the presence and absence of salt, follows similar patterns. Therefore, it is better to salt the beef before freezing rather than during the preparation of the sausage emulsion. These influences of temperature on the ATP depletion in unsalted and salted beef can be explained in terms of the release of Ca(2+) ions from the sarcoplasmic reticulum.