Effects of Multiple Freeze-Thaw Cycles on Protein and Lipid Oxidation, Microstructure and Quality Characteristics of Rainbow Trout (<i>Oncorhynchus mykiss</i>)

Abstract

Multiple freeze-thaw cycles due to temperature fluctuations irreversibly damage the muscle tissue of fish, thereby reducing their edibility. The aim of this study was to determine the effects of the number of freeze-thaw (F–T) cycles on protein and lipid oxidation, microstructure, physical index, and nutritional quality of rainbow trout muscle. The results showed that F–T cycles accelerated protein carbonyl formation and thiobarbituric acid reactive substances (TBARS) generation (p p L* and yellowness b* increasing, while redness a* declined (p p < 0.05) due to the decrease of WHC as well as protein and lipid oxidation. The results indicated that the quality of rainbow trout muscle changed after the third cycle, deteriorated seriously after the fifth cycle, and was unacceptable after the seventh cycle. Therefore, it is necessary to reduce the temperature fluctuation to less than three times during freezing. The results provided a reference for the identification and classification of frozen aquatic products.

Keywords

• rainbow trout
• freeze-thaw cycles
• protein and lipid oxidation
• microstructure
• quality characteristic