Why does my home-made bread go mouldy?

Well, I don't think you're doing anything wrong -- I think it's because you aren't using any preservatives in your bread (and that's a good thing, right?). I find my homemade bread has to be eaten in about a week, but I live in a dry climate. A more humid climate might result in it lasting 3-4 days.

The rate at which your bread will develop mold is mostly dependent on two factors — humidity and the acidity of the bread. A well baked sour dough loaf ( a boule ) will scoff at your garden variety bread mold for at least a week, usually longer. A softer sandwich loaf made from an enriched dough ( e.g. with added sugar ), is much more fragile.

Try cooking your bread a bit longer, and then let it cool completely on a rack before it goes into your bread box. Also, I'd suggest opening the lid to the breadbox while you let the bread cool to let it dry out completely. This should add a few days to your shelf life.

Changing the acidity may be harder to do. I make bread every other day, but I've never used a bread machine, so I can't give you exact instructions. However, to raise the acidity of your dough, you need a longer bulk ferment at a lower temperature. This will increase the amount of lactic and acetic acid your commercial yeast produces. If you can let the mixed dough sit in the fridge for 24 hours, your bread will taste better and last longer. If that simply doesn't work for you, try a "dough enhancer" as these often contain acetic acid and can help keep your bread fresher for longer. You may want to try experimenting with adding a small amount of cider vinegar. But for taste reasons, using the fridge as a "fermentation retarder" is the way to go.

I usually don't use it myself, but adding some salt (3-6 grams would be typical) can somewhat reduce the propensity to mold. Citric acid or a sourdough starter might also help, but will obviously change the flavor quite a bit (salt will also change it somewhat.)

It's also possible that your bread is starting particularly wet, and either should be cooked longer, or needs to be stored (at least initially) in a more-ventilated manner. I generally leave a loaf out overnight the first night, transfer to a paper bag for a few days depending on humidity, and only move to (unsealed) plastic after a few days in paper.

And finally, once there are mold spores around, they are hard to get rid of. A moldy bread box seemed like a good bet, but evidently was not the core of the problem. General and repeated kitchen cleaning may be called for to make a dent in the spores.

I agree with @franko that a lack of preservatives combined with humidity causes mold spores to grow. Just a thought, but because bread boxes are meant to "regulate" the enviroment by restricting airflow, could it be that the bread is too warm when you put it in the breadbox? My thinking is the humidity would be effectively trapped in there resulting in the perfect conditions for mold. Maybe try leaving it on the cooling rack a bit longer?

• White bread (without preservatives) goes mouldy faster than some types of wholegrain breads. (White flour makes a better breeding ground—the simpler the structure, the easier to "digest" for a simple organism such as moulds. More sugar, less salt, less minerals, more humidity, less acidity, etc. all work in favour of the mould.)

• Mould is present everywhere. I have found that it's easier to make good bread or other types of fermented products in the countryside. In a big city such as London, the air quality will have an impact on the shelf life of your bread. In particular, in a constantly changing environment it might not be anything you did differently.

• One way of slowing down the moulding process is to keep the bread in the fridge (or even freezer) and "toast" it before eating. (Toasting will usually revive even stale bread, driving the last bits of humidity into the middle of the bread, the way it was when it came fresh out of the oven.)

I reckon I've solved the problem and, as stated in my original question, it is something I've been doing: my solution is to reduce the amount of water and also oil. I was putting in more water than the recipe suggested, in order to make a 'lighter' loaf - the stone-ground flour I'm using is pretty 'heavy'. I'd also got in the habit of using 2 to 3 tbsp of light Olive oil. All of this worked for several years and my bread was wonderful (according to guests etc) but went mouldy very quickly.The first loaf I've made with less water and much less fat has NOT gone mouldy after five days (my wife has stopped eating any, yes any bread!) but has made a smaller loaf with much denser texture. Tastes good 'tho. So a HUGE thank-you to all of you who posted replies to my plea, while I have placed myself upon the naughty step. BTW the information about mold spores and wooden bins has been very helpful, so I'm still going to try different containers. For me, putting bread in the fridge or freezing it, absolutely ruins it. I like my bread FRESH!

Is there something else that would prevent the loaf moulding so quickly?

You could either install or replace your bread-bin with one that has a UV light. This will kill mold and allow your bread to keep longer.

http://inventgeek.com/uv-mold-free-bread-box/

This probably isn't the type of answer you were looking for but I felt it appropriate for anyone who might not be aware of the benefits of a UV-lit bread box.

Homemade bread will mold fast because of lack of dough conditioners and other unhealthy additives. You can always slice and freeze, unused portion of first day and toast slices as you need them.

Try wrap your bread in clingfilm or store your bread in a new location. I suspect it might also be the temperature in the room, so it might be worth while moving this to a cupboard.

A recipe with less sugar and some salt might help. I follow the Panasonic recipe, and use a bare teaspoon of sugar and the same of salt, and a tablespoon of oil. The bread lasts 3 to 4 days in a bread crock.