Farmed grass carp (Ctenopharyngodon idella) at commercial size were transported to a natural lake for long-term depuration while being food deprived. The effect of depuration time on the quality of fish fillets was investigated based on proximate compositions, textural parameters and flavour characteristics. The results showed that protein and lipids, but not carbohydrates, were the major source of energy for grass carp during depuration and starvation. Textural parameters that included hardness, springiness, gumminess and cohesiveness increased significantly after depuration, as well as water-holding capacity of fish muscle. Taste and odour characteristics of grass carp muscle were obviously changed by depuration based on tests by an electronic tongue and nose. Off-flavour volatile compounds, such as nonanal and hexanal, were reduced after depuration. In conclusion, the quality of grass carp fillets was improved effectively by long-term depuration and food deprivation. More than 20 days of depuration was appropriate for the enhancement of grass carp quality before marketing.
K E Y W O R D Sdepuration, fillet quality, flavour, food deprivation, grass carp
The micro-flowing water system can improve the flesh quality of freshwater fish using the traditional pond farming method. However, the mechanism of this phenomenon has not yet been explored. This study intends to examine the changes of metabolites in freshwater fish after treatment with the micro-flowing purification system (MFPS). The UPLC-QTOF/MS based metabolomics method was utilized to screen the metabolites and predict the major possible metabolic pathways after MFPS treatment. There were 377 types of metabolites identified in the fish muscle, of which 54-71 represented significant different metabolites identified during different stages of MFPS treatments. The main mechanism of MFPS treatment in improving the quality of grass carp fish muscle was investigated, and the MFPS treatment was shown to improve the flesh quality and the flavor of grass carp fish muscle.This study could provide the theoretical basis for improving the quality of aquatic products.
Near infrared reflectance spectroscopy was used to discriminate different species of freshwater fish samples. Samples from seven freshwater fish species of the family Cyprinidae (black carp (Mylopharyngodon piceus), grass carp (Ctenopharyngodon idellus), silver carp (Hypophthalmichthys molitrix), bighead carp (Aristichthys nobilis), common carp (Cyprinus carpio), crucian (Carassius auratus), and bream (Parabramis pekinensis)) were scanned by near infrared reflectance spectroscopy from 1000 nm to 1799 nm. Linear discriminant analysis models were built for the classification of species. We inspected the effect of partial least square, principal component analysis, competitive adaptive reweighted sampling, and fast Fourier transform on linear discriminant analysis. The results showed that the dimension reduction methods worked very well for this example. Linear discriminant analysis models which were combined with principal component analysis and fast Fourier transform could classify accurately all the samples under multiplicative scatter correction pre-processing. According to the loadings in principal component analysis,
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