Effects of Rigor, Salt, Freezing, Lyophilization and Storage Time on pH, Water-Holding Capacity and Soluble Protein Nitrogen in Beef Muscle

Abstract

The water-holding capacity (WHC) of frozen and reconstituted lyophilized (freeze-dried) beef (both pre- and post-rigor) increased (P<0.05) with the increase in salt levels (0, 2 and 4%). Freeze-dried and reconstituted beef had lower (P<0.05) WHC than the frozen control at all salt levels tested. The freeze-drying process may damage some of the beef muscle proteins. The WHC of the freeze-dried beef (both pre- and post-rigor) decreased (P<0.05) with the increase of storage time (10 weeks). Salt (2 and 4%) retarded the glycolysis process in the pre-rigor frozen and freeze-dried beef as indicated by higher (P<0.05) pH values than the post-rigor frozen and freeze-dried beef. The addition of salt (0, 2 and 4%) increased (P<0.05) the extractable soluble protein nitrogen content in the prerigor frozen beef and decreased (P<0.05) the soluble protein nitrogen content in the post-rigor frozen beef. The pre-rigor freeze-dried beef with 2% salt contained (P<0.05) more extractable soluble protein nitrogen than the other two pre-rigor freeze-dried groups (0 and 4% salt). The pre-rigor beef contained more (P<0.05) extractable soluble protein nitrogen than the post-rigor beef at the three different salt levels (0, 2 and 4%) during the 15 weeks of storage.