Abstract
The aim of the study was to investigate the effects of fresh fish oil (FFO) and oxidized fish oil (OFO) diets on the muscle quality of hybrid grouper (♀ Epinephelus fuscoguttatus × ♂ E. lanceolatu). Hybrid grouper were fed with diets containing 9% FFO or OFO for 60 days. Muscle sample were collected at 0, 30, and 60 days and the selected indexes of muscle were measured. Malondialdehyde (MDA), reactive oxygen species (ROS), total cholesterol (TC) and triglycerides (TG) in grouper muscle accumulated gradually with prolonged ingestion time, especially OFO group. Total saturated fatty acids (ΣSAFA) was significantly reduced and total polyunsaturated fatty acids (ΣPUFA) was significantly increased of muscle in FFO group; meanwhile, the muscle ΣSAFA and monounsaturated fatty acids (ΣMUFA) contents in the OFO group were significantly higher than those in the FFO group and the ΣPUFA (especially C22:5n3, C22:6n3) contents was significantly lower than that in the FFO group at 60 days. Consumption of OFO diet for 60 days reduced the diversity of volatile compounds, significantly reduced the content of total esters and increased the content of total aldehydes and total aromatics in grouper muscle. Furthermore, ingestion of OFO diet significantly reduced the mRNA expression of fraction growth factors and antioxidant genes in the muscle of grouper. In conclusion, the increasing MDA content in FO and the oxidative rancidity of PUFA can cause the deterioration of grouper quality and flavor due to oxidative muscle damage.
Highlights
Lipid is an essential nutrient for aquaculture animals and is an important component of tissue cells, it has the function of providing essential fatty acids, storing and supplying energy and saving protein
MDA, total cholesterol (TC), and TG contents of grouper muscle increased with the extend of feeding time of oxidized fish oil (OFO) feed, and the MDA and TG contents were significantly higher than the initial values at 30 d, and the TC contents were significantly higher at 60 days (P < 0.05)
Significant decrease of muscle methionine, phenylalanine, total indispensable amino acid, aspartic acid, serine, glutamic acid, total dispensable amino acid, and total amino acids content in fresh fish oil (FFO) group at 30 days compared to initial values (P < 0.05), and at 60 days they reverted to no significant difference from the initial value
Summary
Lipid is an essential nutrient for aquaculture animals and is an important component of tissue cells, it has the function of providing essential fatty acids, storing and supplying energy and saving protein. HUFAs are susceptible to oxygen, moisture, light and the metal in the feed additives and other factors, very easy to oxidation and decomposition into alcohols, ketones, aldehydes, and other harmful substances in the production, use and storage process (1). It has a serious impact on the health and quality of the animal. The lipid content in the feed of mariculture fish is generally 12– 15% (2), and the farming objects are generally concentrated in subtropical or tropical areas such as high temperature and high humidity, which provides suitable environmental conditions for the oxidation of FO in feed. The problem of FO oxidation in marine fish feed has seriously affected the sustainable development of the mariculture industry
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