The Microbiological Analysis And Preservation Study Of Fresh Water Surimi Products

Surimi based products is currently a kind of customers' preferable fish meat product in China,also have a very large space for development and market potential.In this research,we studied the storage properties and shelf life of fried surimi products and non-fried surimi products under different storage temperature(5 ??10 ??15 ??20 ??25 ?).And the odor analyze of electronic nose was applied to quickly and accurately determine the quality of the surimi products.Conventional plating method and PCR-DGGE of the DNA directly extracted from surimi products(culture-independent method)and from bulk cells from culture media(culture-dependent method)were applied to characterise as many bacteria species as possible.Bio-preservatives such as lysozyme,chitosan and tea polyphenols were selected to determine the optimum concentration range.The orthogonal design was applied to optimize the optimal formula of bio-preservatives.Application and effects of the compound bio-preservatives on surimi based products were evaluated from total viable counts.The main results were presented as follows:1.Study the storage properties and shelf life of fried surimi products and non-fried surimi products under different storage temperature.At different storage temperature(5 ??10 ??15 ??20 ??25 ?),TVB-N value,the total number of bacteria,TBA value were measured to contrast the changes in each index of fried and unfried surimi products.The kinetics models of TVB-N value,bacterial counts and TBA value with respect to storage time and temperature were developed,so as to predict and control the quality of fried surimi product during storage.But non fried surimi product preservation time was too short,do not meet the conditions of kinetic analysis,so it did not establish its dynamic model.The results showed that at 5 ?,10 ?,15 ?,20 ?,25 ? under the conditions fried surimi products shelf life were 8,4,3,2 d and 1 d,rather than fried surimi period were 3,1,1,1,1 d and 1d,and the bacterial count TBA value and TVB-N value increased with storage time and storage temperature.The changes of bacterial count TBA value and TVB-N value with time and temperature showed precision of the first order chemical reaction model and Arrhenius equation.2.The microbial quantity of fried surimi products and non-fried surimi products during 4? storage was investigated.Conventional plating method and PCR-DGGE of the DNA directly extracted from surimi products(culture-independent method)and from bulk cells from culture media(culture-dependent method)were applied to characterise as many bacteria species as possible.No significant difference in spoilage bacteria between fried surimi products and non-fried surimi products could be found during storage period.Plating results showed the major bacterial group was Lactic acid bacteria.In culture-dependent method,Flavobacteriaceae bacterium and Pseudomonas poae were found in all storage period.Psychrobacter sp.were only found in culture-independent method.Traditional plating and culture-dependent methods showed the appearance of cultivable bacteria which were not found in the other two methods.Whereas the culture-independent method could exhibit and identify microorganisms could not grow on media.Thus this study highlighted the benefit of using the traditional plating,culture-independent and culture-dependent approaches to enhance understanding in the spoilage bacteria populations.3.The aim of this study was to investigate the application of an electronic nose(EN)in the prediction of microbial quantities in freshwater-based surimi fried fish cakes stored at different temperatures(5 ?,10 ?,15 ? and 20 ?).EN data were collected from the headspace of the samples in parallel with the data from the microbiological analysis of total viable counts(TVC).Samples from different storage temperatures could be divided into three microbial quantity classes(fresh,semi-fresh and spoiled).Principle component analysis(PCA)confirmed the difference in the volatile profiles of samples from different spoilage classes.Probabilistic neural network(PNN)prediction model was used to quickly determine the microbial quantity class of the fish cakes.Back propagation artificial neural network(BPNN)prediction model was used to establish a correlation between the EN and the TVC.The results showed that PNN did not need training and could quickly determine the spoilage class with 94% accuracy,BPNN demonstrated a correlation of 82% between the predicted and observed microbial population.4.Utilizing orthogonal optimization design that the best inhibition zone by adding 1.5% tea polyphenol,0.75% chitosan and 1.25% lysozyme respectively,which mean that the inhibitory effect was the best under this condition.The verification experiment showed that the compound bio-preservatives significantly inhibited the growth of microorganisms,effectively maintained the quality of surimi based products.