The Research On Preservation Technology Of Trout Fillet And Development Of By-product

Freshwater trout is one of the most cold-water fish species in China at present.As high-grade fish,trout is gradually favourated by consumers in the way of fresh fish fillets.Therefore,the quality and safety issues of commercial trout slices are also deeply concerned by consumers in storage and preservation.At the same time,there were retained a large amount of processing by-products such as fish skin and minced meat when we selected high quality fish fillets.In view of the above problems,the main purpose of this thesis is to study the quality changes of trout fillets treated with defferent packages and biological preservatives under defferent storage temperatures,so as to obtain a preservatived method of combining various preservation technologies for the aquatic products feild.The improvement of the preservation method provides a theoretical reference for aquatic field.Meanwhile,the development of products by using by-products of trout not only improves the comprehensive utilization value of carp by-products,but also enriches the types of trout products.The main conclusions are as follows:(1)Effects of different storage temperatures on quality changes of troutTrout's indexes exceeded the prescribed standards when it was stored for 2 days at 25 °C,and the meat had deteriorated.At 10 °C,the comprehensive sensory was unacceptable when the trout was stored for 4 days.Meanwhile,the volatile base nitrogen value(TVB-N)and the total number of colonies had been exceeding the limiting of standard.At 4 °C,the quality changes of trout were slower.This indicated that the storage temperature was extremely important for the quality change of the trout.The higher the storage temperature was,the faster the rate of microbial growth and nutrients decomposition was.(2)Effects of different packaging methods on quality changes of troutThe physical and chemical indexes of the fish began to change significantly when the vacuum packaging and nitrogen-filled packaging fillets were stored for 6 days.On the 8th day,the TVB-N values of the two groups exceeded limiting standard,while the control group began to decomposition characteristics on the 4th day.Compared with the control group,vacuum packaging and nitrogen-filled packaging could effectively delay the spoilage of trout.At the same time,vacuum packaging was superior to nitrogen-filled packaging in terms of fat oxidation,TVB-N value and pH of trout,but it was poor in trout's texture.(3)Optimization of complex preservativeChitosan,tea polyphenols and lemon juice had inhibitory effects on the TBA value,TVB-N value and total number of colonies of trout during cold storage.By analyzing the experimental results,1.0%,1.5%,2.0% chitosan solution,0.15%,0.20%,0.25% tea polyphenol solution and 2.0%,4.0%,6.0% lemon juice were used to optimize the ratio of preservatives.The optimal combination of the three preservatives was determined by Box-Behnken response surface experimental design.The research indicated that the optimal ratio of the three preservatives was determined as follows: 1.75% chitosan,0.25% tea polyphenol,and 4.98% lemon juice.(4)Application of complex preservative in fresh-keeping of troutThe complex preservative could better maintain trout's sensory quality and texture characteristics,and could effectively delay the changes of TBA value,TVB-N value,total number of colonies and color difference.Compared with the control group.the complex preservative could extend the storage period of the trout by four days.The trout slices were quickly tested by low-field nuclear magnetic resonance(LF-NMR)and electronic nose techniques to analyze changes in moisture content and volatile components during storage.The results indicated that the changes of water distribution and volatile components were in accordance with the results of physical and chemical indicators.(5)Comprehensive utilization of by-products from trout processingUsing the sweet potato puree and processed by-products of trout as the main raw materials,the potato surimi crisp were made by microwave expansion technology.The sensory quality and texture characterstics of the crisps were used as evaluation indicators.The optimum condition of crisps was determined by single factor experiments and orthoganal test.The results showed that the optimum formula of crisps was as follows: with the total weight of surimi and sweet potato as the benchmark,to add 4 % vegetable oil,30 % glutinous rice flour,1.0 % sodium bicarbonate and ammonium bicarbonate with the ratio of 2:1,then the crisps were prepared by using microwave puffing at 500 W for 120 s.The production had complete appearance,uniform color and crispy taste.