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Food Mythbusters: How Bread Goes Stale

Food Mythbusters: How Bread Goes Stale

We tend to think that bread loses its freshness because of dehydration, but the exact opposite is true: bread goes stale because it absorbs too much moisture.

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Few foods are as satisfying and versatile as bread. Think of a fresh roll filled with a slice of raw ham or hazelnut chocolate spread. Without forgetting stale bread, which is the basic ingredient of many soups (such as Tuscan Ribollita) and lots of other delicious recipes. This does not alter the fact that stale bread is a “leftover” which goes hard and loses its fragrant taste after a few days. Some people even buy more bread than they need and allow it to go stale so that it can be used in a number of tasty dishes. But if you make yourself a sandwich and pull a face at the first bite, the inevitable comment will be: “This bread has gone stale!”

We tend to think that bread loses its freshness because of dehydration. This is what the symptoms seem to indicate: dryness and lack of taste. In actual fact, the exact opposite is true: bread goes stale because it absorbs too much moisture. Hard to believe, isn’t it? For an explanation of this phenomenon, it is necessary to consider what bread is made of: flour and water basically. Which means, starch. A great deal of starch. You may already know that starch is a carbohydrate mainly made up of amylopectin and, to a lesser extent, of amylose. When starch comes into contact with water and, consequently, when bread absorbs moisture, the phenomenon of “starch retrogradation” takes place. It is mainly the amylopectin which manifests this reaction, causing the starch to return to its original crystalline structure.

So, if it is true that we reduce moisture by baking bread, when we add water and increase the amount of moisture, we trigger the opposite process. This is not sufficient to recover the former condition of the starch contained in the flour, but an intermediate phase ensues: the amylose chains become closer to each other and amylopectin crystals become larger. As the retrogradation process continues, water passes from the bread to the outer crust: this is why bread goes stale. Initially it tends to go hard in the centre while the crust loses its crispness. Then, of course, if the bread is VERY old, it loses all of its moisture and becomes dry, but that’s quite another story.

Now that we have exploded the myth, let’s address the practical side of the question: what is the best way to store bread? Alternatively, how can we make bread go stale more rapidly when we want to add it to our soups? The retrogradation of starch takes place most effectively at a temperature between 0 and 10°C, with a peak at 4°C. Consequently, the fridge is the WORST place in which to store bread. Even if you put it in special storage boxes, temperature is the biggest obstacle. Against that, retrogradation is slowed down and almost curbed at temperatures below -18°C. Therefore, the best solution is to put your bread into a paper bag and pop it into the freezer. When you need it can be thawed out, from frozen, in an oven set at a low temperature or a microwave: it may not taste as it does when freshly baked, but almost. On the contrary, if you need stale bread in a hurry, put it in the fridge, on condition that there is not too much humidity, which would cause the formation of mould. Then, if you make your own bread (well done!), and you want it to stay fresh for as long as possible, the secret is to use protein-rich flours such as manitoba: the more protein, the less starch there will be, with a consequent slowing down of the ageing process. Isn’t it amazing how much science there is an old piece of stale bread?

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