Stale bread can have a second life, both in home and industrial kitchens. However, there is a use that cannot be given to this food: recycle it to make more bread from it. During the baking process, temperatures above 100 ⁰C are reached, so the proteins are denatured. Gluten, the protein that allows wheat flour to become an extensible dough and retain gas from fermentation, loses its functionality.
That is why we cannot use a flour made from bread to re-make bread. At most we could incorporate it in small proportions, to the detriment of the quality of the final product. In addition, when the starch is heated in the presence of water, it gelatinizes to increase the consistency of the dough. This is irreversible, so a flour obtained by grinding bread cannot thicken in the same way than a wheat flour when heated with water.
Finally, it must be taken into account that the crust reaches temperatures much higher than those inside the pieces. These reach 200 ⁰C and produce the Maillard reactions that give bread its toasted color. The compounds that are generated in these reactions also give a certain bitter taste: bread with more crust, or more toasted, when ground, they generate darker and slightly more bitter flours.
Once we know what it is no we can do with stale bread let’s see what we can do.
Quick and easy: toast it
The easiest way to reuse bread is to toast it. With this simple operation, the bread goes from being a hard and rubbery product to a very pleasant product. The bark finishes drying and goes from leathery to dry. In the crumb, the reactions that have caused its hardening are partially reversed, so it softens.
If we want to make a toast, it is convenient that the bread is not completely hard, since, in that case, it is difficult to break it without breaking, the crumb is not able to reverse its hardening, and the result is less pleasant. If we add some ingredient to the top we can get a panini.
French toast, soups and puddings
Stale bread captures water to recover the liquid it has lost when it dries. Once rehydrated it can be fried or used as a thickener in recipes. One of the most common formulas to reuse bread is torrijas or french toast. In this case, the bread is rehydrated with milk, and later coated with egg and fried. This formula has many variants with different types of bread and ingredients such as syrup, sugar, honey, wine and cinnamon, among others.
Another way to rehydrate bread is to add it to sauces as a thickener. For example, in soups – cold or hot – such as salmorejo, Castilian soup, garlic and onion. We can take advantage of it for many sauces and purees, although it must be borne in mind that it would not thicken as much as a flour after heating it.
We can also use bread —as well as remains of bakery products, such as cakes— to thicken and give a special texture to certain dairy desserts, like puddings and Calatrava bread. They are recipes that are reminiscent of flan, but with the addition of bread. Lastly, it can be used as a thickener in certain meat products, such as meatballs.
Crumbs and breadcrumbs
If we cut the bread we can also rehydrate it to make crumbs. In this typical Castilian dish, the sliced bread is rehydrated and fried together with some flavoring, such as garlic, and some meat product, such as chorizo or bacon. So the breadcrumbs are juicy and they acquire the flavor of the products together with those that are cooked.
Another possibility is to prepare croutons. To do this, we only have to fry (or toast) the pieces of bread. Thus, crisp even when incorporated into sauces, purees and consommés. These pieces can also be used in salads, such as panzanella, typical of Italian Tuscany, although there are people who prefer to add moistened bread, without toasting.
If we chop the bread to obtain a finer product we have breadcrumbs, which can be used to bread fish, meats and even vegetables. This bread is easy to get with any domestic chopper or food processor. The final particle size is important, since the breads, depending on their thickness, give rise to different textures that absorb oil differently, which affects the result.
The best thing is to try different granulometries and see which one convinces us the most. If we have a strainer we can try to separate the part of the breadcrumbs that passes through the strainer from the one that is retained in it and test both separately. We will see that the final texture changes.
If we manage to grind the bread to the fineness of a flour we can use it as a thickener, but also to make cookies, sweets or savory. It is enough to substitute the flour of any cookie formulation for this one. The results are not identical, but very interesting cookies can be obtained. However, it is not possible to use them to make breads or cakes due to the loss of properties that we have discussed. In these cases we can incorporate this flour in small quantities.
What does the industry do?
The flour is composed, for the most part, of starch granules. These break down during the baking of the bread and are accessible to enzymes, capable of breaking it down into simple sugars, such as maltose and glucose. In fact, the remains of bread could be used to make a sweet syrup.
The most interesting thing about these sugars is that they constitute a perfect nutrient for certain microorganisms, so can be used to make fermented products. In the bakery industry, stale bread – ground or rehydrated – is used to make sourdoughs.
This bread provides interesting nutrients for the lactic acid bacteria responsible for the process. Already exist bakeries that boast of this reuse of bread. In the same way The use of these flours in the production of products similar to yogurt could be studied, since the responsible bacteria can feed on the glucose present after enzymatic hydrolysis.
Stale bread can also be used to make beer. Most beers incorporate some source of fermentable sugars in addition to barley malt. These can be obtained from the breakdown of starches in bread by malt enzymes to generate maltose and glucose.
Using discarded bread for brewing beer started in England, where the first beer of this type was marketed, but It has spread throughout the world, mainly through craft breweries. It could also be used to make other alcoholic beverages, after distillation.
There are other alternatives for the use of stale bread, such as its use in feed, and the Dutch project that collects the bread that is discarded to make compost. However, the least environmental impact occurs when the by-products of the food industry are reincorporated into human food. It is a low-cost ingredient with which to make new dishes and explore new textures.
* This article was originally published on The Conversation.
** Manuel Gómez Pallarés is a professor in Food Technology at the University of Valladolid.