Contents lists available at ScienceDirect Food Control journal homepage: www.elsevier.com/locate/foodcont Efect of air blast freezing and frozen storage on Escherichia coli survival, n-3 polyunsaturated fatty acid concentration and microstructure of Greenshell™ mussels Manasweeta Angane a,b , Sravani Gupta b , Graham C. Fletcher b,c , Graeme Summers b , Duncan I. Hedderley d , Siew Young Quek a,e,∗ a Food Science, School of Chemical Sciences, The University of Auckland, Auckland, 1010, New Zealand b The New Zealand Institute for Plant & Food Research Limited, Auckland, 1142, New Zealand c The New Zealand Food Safety Science & Research Centre, New Zealand 1 d The New Zealand Institute for Plant & Food Research Limited, Palmerston North, 4442, New Zealand e Riddet Institute, New Zealand Centre of Research Excellence for Food Research, Palmerston North, 4474, New Zealand ARTICLEINFO Keywords: Escherichia coli Greenshell™ mussels Air blast freezing Frozen storage n-3 polyunstaturated fatty acids (PUFA) Microstructure ABSTRACT This study highlighted the efect 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 diferent 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 signifcantly reduce the non-pathogenic E. coli counts in the Greenshell™ mussels. However, subsequent frozen storage at −10°Cand−20°Cforaperiodof84daysresultedin>1log 10 reduction in E. coli counts. Although, the use of diferent temperatures (−10°C and −20°C) did not show statistically signifcant (p =0.069) impact on E. coli counts, but based on the regression analysis, storage at −10°C was slightly more efective 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 efect offrozenstorageontwocomponentsbenefcial 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 signifcantly (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 signifcantly (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. 1. Introduction There has been demand for green-lipped mussels (Perna canaliculus) in New Zealand since the late 1920s (Greenway, 1969). However, no- teworthy production and marketing of the species as Greenshell™ mussels started in New Zealand in the late 1970s when they were re- cognized as a supreme quality eating mussel (Jefs, Holland, Hooker, & Hayden, 1999). Molluscan shellfsh such as oysters, mussels, clams and scallops flter feed on the organic material found in their surrounding marine environments. Filter-feeding shellfsh can accumulate microbial contaminants including enteropathogens such as Salmonella in their tissues (Baker, 2016; Dixon Donnison, Harfoot, & McDonald, 2007). Escherichia coli is a major constituent of the microfora of the mam- malian intestinal tract and faeces. Although a few strains are highly pathogenic to humans (Nataro & Kaper, 1998), most are non-patho- genic. Non-pathogenic E. coli are usually harmless; but they can https://doi.org/10.1016/j.foodcont.2020.107284 Received 29 December 2019; Received in revised form 26 March 2020; Accepted 28 March 2020 ∗ Corresponding author. Food Science, School of Chemical Sciences, The University of Auckland, Auckland, 1010, New Zealand. E-mail addresses: mang207@aucklanduni.ac.nz (M. Angane), Sravani.Gupta@plantandfood.co.nz (S. Gupta), Graham.Fletcher@plantandfood.co.nz (G.C. Fletcher), Graeme.Summers@plantandfood.co.nz (G. Summers), duncan.hedderley@plantandfood.co.nz (D.I. Hedderley), sy.quek@auckland.ac.nz (S.Y. Quek). 1 https://www.nzfssrc.org.nz/. Food Control 115 (2020) 107284 Available online 02 April 2020 0956-7135/ © 2020 Elsevier Ltd. All rights reserved. T