Sie befinden Sich nicht im Netzwerk der Universität Paderborn. Der Zugriff auf elektronische Ressourcen ist gegebenenfalls nur via VPN oder Shibboleth (DFN-AAI) möglich. mehr Informationen...
Effect of air blast freezing and frozen storage on Escherichia coli survival, n-3 polyunsaturated fatty acid concentration and microstructure of Greenshell™ mussels
This study highlighted the effect of air blast freezing and frozen storage on non-pathogenic Escherichia coli in Greenshell™ mussels (Perna canaliculus). Greenshell™ mussels were inoculated with a cocktail of 10 different strains of E. coli and their survival was monitored over a period of 84 days. Two freezing temperatures (−10 °C and −20 °C) and two inoculum concentrations, i.e. moderate (104 colony forming units/g (CFU/g) and high (107 CFU/g) were used. Enumeration of E. coli was carried out at regular intervals using the conventional ‘most probable number’ (MPN) and by SimPlate® methods. Results show that air blast freezing did not significantly reduce the non-pathogenic E. coli counts in the Greenshell™ mussels. However, subsequent frozen storage at −10 °C and −20 °C for a period of 84 days resulted in >1 log10 reduction in E. coli counts. Although, the use of different temperatures (−10 °C and −20 °C) did not show statistically significant (p = 0.069) impact on E. coli counts, but based on the regression analysis, storage at −10 °C was slightly more effective at inactivating E. coli. Furthermore, compared to the conventional MPN method, the SimPlate® method was less sensitive and the correlation value between the two methods was found to be r2 = 0.81 and r2 = 0.75 for −10 °C and −20 °C, respectively. This research also investigated the effect of frozen storage on two components beneficial for health: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and on microstructure changes during frozen storage. The total n-3 polyunsaturated fatty acid (PUFA) concentrations reduced significantly (p < 0.05) after storing Greenshell™ mussels at −10 °C for a period of 84 days but the total n-3 PUFA levels did not reduce significantly (p > 0.05) in mussels stored at −20 °C. In addition, the microstructure analysis revealed that frozen storage caused serious deformity in tissue structure of Greenshell™ mussels.
•Average E. coli numbers reduced by 1.48 log10 units over 84 days frozen storage.•Frozen storage is an effective method for reducing E. coli counts in mussels.•Frozen storage caused serious deformity in microstructure of Greenshell™ mussels.•EPA concentration did not reduce significantly (p > 0.05) upon frozen storage.•SimPlate® method was less sensitive than the conventional MPN method.