Effects of multiple freezing (-18 +/- 2 degrees C) and microwave thawing cycles on the quality changes of sea bass (Dicentrarchus labrax)

Abstract

Sensory, chemical [ pH, total volatile basic nitrogen (TVB-N), trimethylamine (TMA-N), thiobarbituric acid (TBA)] and composition (crude protein and crude lipid) analyses were carried out on whole, gutted and fillets of seabass that were frozen (-18+/-2 degrees C) and thawed more than once in microwave. It was detected that the sensorial acceptability values decreased certainly for all fish samples (whole, gutted and fillets of sea bass) when compared with control group. While chemical (pH, TVB-N, TMA-N, TBA) values increased, crude protein and crude lipid values decreased after the multiple freezing and thawing cycles under microwave. The obtained results offered that thawing by microwave is not appropriate sea bass because of the undesirable cooking effect of microwave to the some parts of fish such as tail, eye and fins. Also skin dryness, moisture losses in eye fluids and textural deteriorations were observed. Significant differences (P< 0.05) were found in general acceptability values and pH, TVB-N, TBA and crude protein results among the sea bass groups thawed in microwave conditions.