Changes Of The ATP-related Compounds And Biochemical Properties Of Silver Carp During Early Stage Post-mortem And Chilled Storage

Silver carp is the most abundant freshwater fish in China. It is highly spoilage because it is rich in water content, protein and fat. Deterioration of fish normally follows four stages:rigor mortis, resolution of rigor, autolysis (loss of freshness) and bacterial spoilage. However, there are little reports about the biochemical properties change of silver carp during early post-mortem and chilled storage. Therefore, this paper aimed to investigate the early post-mortem changes and IMP content of silver carp. The changes of sensory evaluation, microbiological and biochemical characteristics of silver carp during chilled storage were also studied. The quality predicted models between-3and15℃and the artificial neural networks model of IMP change ratio during thermal treatment were established. In addition, this study explored the effectiveness of grape seed and clove bud extracts in terms of lowering the oxidation rate of lipid and protein and extending the shelf life of silver carp fillet. This paper provided the theoretical knowledge of silver carp during early post-mortem and chilled storage.1. Changes of the physicochemical parameters and ATP-related compounds of silver carp stored at4℃,0℃and in ice during72h post-mortem process were studied. The increase of K value, electrical conductivity (EC) and the decomposition of ATP-related compounds were inhibited by lower temperature. Water holding capacity (WHC) and texture parameters reached the highest measured values at2h post-mortem regardless of the storage temperature, while the highest ATP concentration occurred at2,2and8h after slaughter at4℃,0℃and in ice respectively. This result suggests that it might be better to consume and process silver carp in2-4h postmortem after slaughter.2. The effect of lightly salt and sucrose on post-mortem changes of silver carp during72h at4℃was evaluated. Curing of silver carp with1.8%salt or1.8%salt+1.8%sucrose could enhance WHC and texture parameters and reduce the cooking loss during72h post-mortem process at4℃. Additionally, dry-cured silver carp had higher level of IMP compared with untreated samples. For silver carp with1.8%salt or1.8%salt+1.8%sucrose, the highest IMP concentration measured occurred at4h, texture results suggested that hardening last about4h. It is highly recommended that the better eating time of dry-cured silver carp was4h post-mortem after slaughter.3. The changes of IMP concentration and IMP change predictive model in control and silver carp with1.8%salt during heat treatment and post-mortem process were studied. The highest IMP amounts of control and T1occurred in both10min at85℃and storage after3days and1day at4℃respectively. The relative errors of IMP for the testing set in control and silver carp with1.8%salt less than16%and15%between measured values and predictive values. Therefore, the implementation of the artificial neural network with back-propagation algorithm (BP-ANN) in untreated and salted silver carp provide good prediction capability for cooking temperatures from50to85℃and storage times from day0to day3.4. Quality changes and predictive kinetic models of silver carp fillets stored under variable temperatures were studied. Lower temperatures were able to inhibit the increase of electrical conductivity (EC), total volatile basic nitrogen (TVB-N), total aerobic bacterial count (TAC), biogenic amine and the decrease of sensory acore. The relative errors of EC, TAC and sensory score of silver carp fillets were less than13%and the relative error of TVB-N was under13%in12days storage between measured values and predictive values. Therefore, the kinetic predictive equations provide convenient models for evaluating and predicting the freshness and quality for silver carp fillets within-3℃-15℃. As the predominating biogenic amines in silver carp fillets, putrescine was significantly correlated with TVB-N, TAC, sensory evaluation, tryptamine, phenethylamine, which makes the putrescine a potential quality marker of silver carp fillets.5. The aim of this study was to investigate the utilization of clove bud extract (CBE) and grape seed extract (GSE) as natural antioxidants for retarding lipid and protein oxidation in silver carp fillets stored at4±1℃. The addition of grape seed extract (GSE) and a20-times dilution of clove bud extract (CBE20) retarded the increase of hydroperoxide (PV) and thiobarbituric acid (TBA); protected against decreases of L*value, salt-soluble protein content and total sulfhydryl group. Therefore, GSE and CBE20can be employed as natural antioxidants to prevent lipid and protein oxidation and extend shelf life of silver carp fillets at4℃.