Effect of air blast freezing and frozen storage on Escherichia coli survival, n-3 polyunsaturated fatty acid concentration and microstructure of Greenshell™ mussels. (September 2020)

• Record Type: Journal Article
• Authors: Angane, Manasweeta; Gupta, Sravani; Fletcher, Graham C.; Summers, Graeme; Hedderley, Duncan I.; Quek, Siew Young
• Is Part Of: Food control. Volume 115(2020)
• Publication Date: 2020-09
• Subjects: Escherichia coli -- Greenshell™ mussels -- Air blast freezing -- Frozen storage -- n-3 polyunstaturated fatty acids (PUFA) -- Microstructure; Food -- Quality -- Periodicals; Food -- Analysis -- Periodicals; Food handling -- Periodicals; Food industry and trade -- Quality control -- Periodicals; Aliments -- Industrie et commerce -- Qualité -- Contrôle -- Périodiques; Aliments -- Qualité -- Périodiques; Aliments -- Analyse -- Périodiques; Hygiène alimentaire -- Périodiques; Food -- Analysis; Food handling; Food -- Quality; Periodicals; Electronic journals; 664.07
• DOI: 10.1016/j.foodcont.2020.107284
• Languages: English
• ISSNs: 0956-7135

Abstract

Abstract: 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 (10 4 colony forming units/g (CFU/g) and high (10 7 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 r 2 = 0.81 and r 2 = 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. Highlights: Average E. coli numbers reduced by 1.48 log10 units over 84 days frozen storage. F rozen 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.