The effects of slow and quick freezing methods on microstructure, drip loss, proximate compositions and sensory properties of Nil Tilapia (nilticus Oreochromis) fillets

The aim of this study was to investigate the effects of slow and quick freezing on the changes in sensory properties, drip loss, microstructure and proximate compositions of Nile Tilapia (Oreochromis niloticus) fillets. For this reason, skined off and deboned tilapia fillets were frozen by slow and quick freezing methods. The samples were packed and stored at -18 °C for six months. Proximate composition, drip loss, and sensory evaluation of the samples were determined on a montly basis. Microstructure of the samples was studied using Scanning Electron Microscopy (SEM) every second month. Results indicated that fresh tilapia fillets had 1/30, 18/70, 1/85, 79/12 percentage of fat, protein, ash and moisture contents, respectively. The amounts of proximate compositions were changed during the storageperiod. Quick frozen samples had significantly lower changes than slow frozen samples. The percentage of the drip in the slow frozen samples was significantly higher than quick frozen samples. SEM micrographs were also showed that the changes in the microstructure of the samples were different in the slow and frozen samples. Slow freezing method resulted in the higher damage in the microstructure of the samples than quick freezing method. Sensory evaluation of the samples indicated a better acceptability for the quick frozen samples than that for slow frozen sample.