EFFECTS OF VARIOUS THAWING METHODS ON PHYSICOCHEMICAL AND STRUCTURAL PROPERTIES OF BEEF

Abstract

The effect of four meat thawing techniques including chill temperature, room temperature, tap water and microwave on quality characteristics, lipid oxidation, proteins degradation, microbial spoilage and the microstructure of beef longissimus lumborum muscle were compared. A fresh portion of longissimus lumborum muscle was obtained from eight beef carcasses after 24 h postmortem. The findings indicated that all of the thawed samples, particularly the microwave beef samples, had a markedly worse quality than those of fresh meat. Among the thawing methods, changes in the beef quality of the chill temperature samples were significantly less. The increases in malondialdehyde value and decreases in free thiol content indicated that proteins and lipids in the beef samples subjected to room temperature, tap water, and microwave thawing methods were oxidized while thawed beef at a chill temperature did not significantly affect the lipid-protein oxidation compared to fresh beef. The greater myosin degradation was observed in room temperature, tap water and microwave thawing treatments, while actin degradation was not affected. Higher growth of total bacterial counts was presented by samples subjected to tap water and at room temperature thawing compared to microwave and chill temperature thawing. The sensory traits of the chiller thawing method were better than those of other methods. Images from scanning electron microscopy demonstrated that the myofibril configurations in the thawing samples were more loose than in the fresh beef samples, which had a compact and organized structure. This was demonstrated by the thawing samples' evidently higher myofibril gap value.

Keywords

• beef quality characteristics
• electrophoresis
• freezing-thawing
• oxidation stability
• microbial spoilage