Does freezing food kill bugs? And are open mussels at the supermarket safe?

Does freezing food kill bugs? P. Moon

No. Some microbiologists actually use the freezer to store bacteria. In fact one of the two last remaining samples of the smallpox virus is kept in test tubes in a freezer at the United States Centre for Disease Control and Prevention in Atlanta, Georgia.

My partner contacted a hideous virus from frozen raspberries grown in Chile while she was pregnant with our first daughter. The group most affected by a recent outbreak of E. coli in the US, attributed to frozen chicken quesadillas, were older teenage boys.

Although the instructions on the packet instructed consumers to cook well before serving the quesadillas, it is thought that hungry 17-year-old boys were simply warming the junk food up but not enough to kill the bugs. Microwaves ovens are notorious for heating food unevenly hence you'll often read instructions to move food around the microwave and allow the food to sit to let the heat distribute evenly. So freezing doesn't kill bugs but heat does. Next.

I was looking at the 'fresh' seafood at our local supermarket and noticed that most of the green-lipped mussels were open. Surely they should be closed. P. Watson

The mussels are dead. Green-lipped mussels, or Perna canaliculus, come all the way from New Zealand. Our quarantine laws mean that they are cooked in the Land of the Long White Cloud before being frozen then exported. Once dead, the adductor muscle no longer holds the mussel closed which is why the defrosted green-lipped mussels were gaping open. Nothing to see here, move on.

Our dinky di, true blue Aussie mussels are called Mytilus galloprovincialis or blue mussels. Right now they are heading into spawning season over winter. This means there could be some variability in quality so you might find some really plump ones or some flagging from post-coital fatigue.

Despite their condition they are still alive when you buy them. Sort them by discarding ones with broken shells. Blue mussels with an open shell should close when tapped. And you'll have heard it a dozen times before, if a mussel doesn't open when cooked, don't chuck it out, pry the stubborn little mongrel open with a knife. And try this one time. Take mussels, clean and scrub them then lay them on the BBQ whole. After a minute or so remove and serve with aioli.

Letters, Corrections and Apologies

Last week we were discussing Devonshire teas, or cream teas as they are known in England. R. Boswell wrote "I do believe that the correct way to open a Devon scone is to break it open with the hands, never cut it, and cover with a thin slab of cold salted butter, a layer of jam then clotted cream. You then get all the primary tastes (even bitter if the jam is good) along with the different textures and temperatures." Thank you. I'll just go and put the kettle on.

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