I just came back from holidays, and the first thing I did after dropping my bags was reaching for a couple of slices of bread from the freezer. I was starving! This simple act has prompted a number of questions in relation to freezing/thawing practices and bacteria!

When I got the bread out of the bag I realised the bread wasn't fully frozen - it was cold  but definitely soft to the touch. My first though as I was putting the slices in the toaster of was: "Urgh, I'll need to check the freezer, probably de-frost it". As I was eating the bread, I thought: "It tastes OK. And the Best Before was only last week, anyway - so it's probably been slowly going off in the freezer. And probably the heat in the toaster killed the bacteria". A while after I had finished eating, and with some (psycho-somatic?) belly-aches starting to worry me, I started wondering whether I shouldn't have eaten that bread at all, and whether bread was actually more innoucuos than, say, chicken or eggs with regards to bacteria!

So my question for you is: what are the chances that this bread has allowed for harmful bacteria to develop? How much does the type of food matter? Is a state between freezing and refrigerating better or worse for bacteria growth? Can toasting kill bacteria?


Very low. Bread is a poor substrate for pathogenic bacteria. The kind which make you sick are almost always found growing on meat or other animal products. You are, after all, made of meat! The most harmful thing you might find is some fungus, some of which can be a little toxic, but they probably won't cause an infection.

Basically, the colder it gets, the slower things grow, so the colder the better. Typically, fridges tun between 2-7 degrees C, freezers at around -15 degrees C. A good rule of thumb is that once it gets cold enough for the water to be frozen, you can be confident that there is little to zero growth going on.

Toasting can certainly kill bacteria. Heating is a highly effective sterilisation method.