| Coregonus peled is a kind of high quality aquaculture fish which is worth popularizing with high economical value and nutritional value.However,due to the high content of nutrients,and spines easily detached body after water,Coregonus peled is highly susceptible to microbial contamination and enzyme activities in the process of fishing and selling,it causes oxidation and degradation of unsaturated fatty acids,and proteins partially decomposed into peptides and amino acids,resulting in peculiar smell,discoloration and texture changes,which seriously affects its freshness and reduces its edible value.Therefore,it is of great significance to take reasonable and effective preservation technology to control the decline of freshness quality of Coregonus peled and prolong the shelf life during storage.Systematic and comprehensive evaluation and analysis of the nutritional quality of Coregonus peled were investigated,and the method of quality evaluation was perfected.Based on the quality analysis,the technology of fresh-keeping logistics was improved,and a comprehensive preservation technology of Coregonus peled was established,so it has important guiding significance for its fresh-keeping processing and high value and high quality utilization.The main research results are as follows:1.Quality Evaluation and analysis of Coregonus peled were studied.The results showed that:(1)The content of crude fat was much higher than that of other fishes,up to 13.87%.The content of the moisture and ash was lower than other fish species,respectively 69.55% and 1.14%.The content of crude protein was only inferior to the Atlantic salmon,which was 18.93%.(2)The content and composition of amino acids were completely conforms to the FAO/WHO standard,according to the evaluation results of AAS,CS and EAAI showed that the essential amino acids were complete and well balanced,so it could provide a good source of protein.(3)The content of unsaturated fatty acids was higher than that of saturated fatty acids,which the content of n-3 PUFAs was 38.17%,especially the content of EPA and DHA accounted for 13.28%and 23.12% of total fatty acids.(4)28 volatile flavor compounds were detected from the experiment,of which aldehydes accounted for a significant ratio of 48.13%,and contributed to the characteristic odor of fishes.(5)Coregonus peled was considered as a kind of delicious taste fish.The content of flavor amino acids accounted for 6.1% oftotal free amino acids,which was one of the important reasons for its delicious meat.The content of IMP in three nucleotides of IMP、GMP、AMP was the highest,which made the greatest contributions to the delicious taste of Coregonus peled.2.The change of freshness quality of Coregonus peled though the whole fish,fish section and fish fillets after 6 days under 4 ℃ storage were studied,through analyzing the change rule of physicochemical and microbial indexes.The results showed that:(1)Sensory quality,color values and texture characteristics were significantly decreased(p<0.05),the descent rate of the whole fish groups was the fastest.(2)K value,TBA value and aerobic plate count showed an upward trend,the change degree of fish fillets groups was remarkably lower than that of the whole fish groups and fish section groups(p<0.05).(3)Comprehensive analysis of key indexes showed that: the sensory quality of Coregonus peled was better after the treatment of fish fillets,it could effectively inhibit the growth and reproduction of microbes,slow down the degradation of ATP and lipid oxidation and deterioration,and maintain good freshness,so as to achieve the purpose of long-term preservation.3.In this paper,using Coregonus peled fillets as the research object,effects of different storage conditions on quality change of Coregonus peled were studied,through analyzing the change of freshness indexes under storage 6 days.The results showed that:(1)Sensory quality,color values and texture characteristics were significantly decreased(p<0.05),the rate of descent of the experimental group at 4 ℃ was the fastest.(2)K value,TBA value and aerobic plate count showed an upward trend,the trend of partial frozen group was remarkably lower than that of the other two groups(p<0.05).(3)From the comparison of key indexes such as K value,TBA value and aerobic plate count,-3 ℃ storage could effectively inhibit microbial infection,reduce lipid oxidation and deterioration,and the first grade freshness could be extended to 3 days,so it could achieve a good effect to prolong high quality fresh-keeping period.(4)According to the analysis of different indexes,the quality changes of Coregonus peled fillets could be accurately reflected by K value,TBA value and the number of microorganisms.4.Effects of tea polyphenol,chitosan and lysozyme for the preservation of Coregonus peled were investigated by orthogonal experiment after 6 days under-3 ℃storage.The results showed that:(1)The best compound preservative was obtained on the basis of the concentration of tea polyphenols was 0.1 g/kg,chitosan was 4.0 g/kg and lysozyme was 0.5 g/kg.(2)Sensory quality,color values and texture characteristics were significantly decreased(p<0.05),and K value,TBA value and aerobic plate count were remarkably lower than the control group(p<0.05)after treatment with the best compound preservative.(3)With the first grade freshness(the K value less than 20%)as the evaluation standard,the control group was stored for 3 days to reach the endpoint ofraw food,and treated by complex preservatives could be extended to 4 days,indicating that the compound preservative could increase preservation time,and achieve a good fresh-keeping effect.To sum up,the comprehensive preservation technology based on the partial frozen storage and the compound preservative could maintain good freshness quality of Coregonus peled,effectively inhibit the microbial growth and endogenous enzymes activity,postpone the corruption and deteriorate,prolonging fresh-keeping time and expand the scope of sales,and make more areas of the country could taste the original ecology fresh fish meat of Coregonus peled.Therefore,the results provide theoretical guidance and reference basis for the fresh-keeping processing and logistics transportation of Coregonus peled. |
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