Investigating on the effect of freezing in different time periods on the chemical and qualitative changes of fish (Giant trevally)

Abstract

Changes in proximate composition of the Giant trevally were carried out for 0 days, 7 days, 14 days, 21 days, 28 days and 35 days at a freezing temperature. The moisture, ash, protein and fat contents were measured using standard methods. Based on obtained results, moisture content was decreased during different periods of freezing and its amount in fresh fish before freezing was (74.72%) that were decreased to 73.5%, 71.74%, 70.4%, 69.06% and 67.72%, respectively  for 7, 14, 21, 28 and 35 days of freezing. The fat content in the fresh fish before freezing was (8.13%) that were decreased to 7.02% and 5.93%, and 5.33%, and 4.73%, and 4.13%, respectively, at 7, 14, 21, 28, and 35 days of freezing, respectively. The amount of protein in the fresh fish before freezing was (20.02%) that were decreased to 18.23% and 16.99%, and 15.75%, 14.51% and 13.27%, at 7, 14, 21, 28 and 35 days of freezing, respectively. Ash content in fresh fish before freezing was (1.21%) that decreased to 1%, 0.82% and 0.70%, and 0.58% and 0.46%, during 7, 14, 21, 28 and 35 days of freezing, respectively. it can be concluded that the best quality of frozen fish  was obtained  between 14 to 7 days of freezing.