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Facts and fiction about food and cooking, by Peter Aitken
Bread becomes stale by drying out
November 19, 2011Posted by on
Stale bread – yuck. The crumb (the part inside) gets hard and stiff and the crust loses any crispness it might have had. Most people attribute this to drying out, but the opposite is in fact true. The bread is actually absorbing moisture, as shown by an increase in weight as the loaf goes from fresh to stale. The moisture absorbed by the crumb causes the starch granules to crystallize, hardening the bread. This is why the fridge is a bad place to store bread, even when it is well-wrapped, because low temperatures speed up the starch crystallization process (although freezing bread is fine because starch crystals don’t form at freezer temperatures). It’s also why a brief visit to the oven can improve stale bread, because the heat drives out some moisture and helps melt the starch crystals.
Bread can dry out, of course, but that’s another matter.
Aha! Just in time for Thanksgiving. Does this explain why croutons dried in the oven taste and hold their shape better than air-“dried” croutons when used for stuffing?
I don’t know – you may be right.
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Where is your proof of this?
I, too, would like to hear the science behind this explanation.
I know that the Myhrvold books are hard to get at. I summarized the material in the original post, there’s not much more I can add. I was surprised by this, too.
Please see “Modernist Cuisine” by Nathan Myhrvold.
Rather difficult for most of us to refer to a 5 volume, $600 text. Can you sum up the crux of the related passages here?
Can you cite any actual science to back this up? Whether or not you’re right, it sounds a bit like alchemy with no sources.
Why is it our responsibility to look up YOUR sources? This article has absolutely zero backing.
I gave my source in a response to another comment. Pay attention, please!
How do you keep the green stuff from growing on bread if you don’t refrigerate it? I refrigerate my bread so it lasts long enough for me to eat it, instead of throwing partial loaves away.
If the bread is sliced, I suggest freezing it – I do this all the time. Then take out 1 or 2 slices and thaw as needed, or you can toast it directly.
Most of what he writes is in agreement with AIB (american institute of baking) texts. But there are also a number of other factors he has left out, such as the changes the gluten goes through during the life of the loaf.
Thanks – would you be willing to post some of this information? I’d be interested and other readers as well, I think.
This is why a breadbox was invented. Keeps the bread at room temperature, with some air circulation to prevent mold, but sealed enough to keep pests out. Bread will keep longer at even warmer temperatures, but warmer temperatures encourage mold growth.
Thank you for your tips.
Thank you! I have refused to put bread in the fridge (unless it’s a sandwich that needs to keep cold) for my entire life. I just always thought something wasn’t right about it. My parents still flip out on me for leaving bread on the counter… Totally going to show them this!
As a chemist (retired) I would like to comment on the staling of bread and why freezing is preferred over refrigeration when dealing with starch-based items such as bread or even cooked rice.
It has to do with a process called retrogradation, in which gelatinized amylopectin starch molecules are cooled below the gelatinization temperature. In gelatinization, both amylose and amylopectin forms of starch absorb water and lose some of their native crystallinity.
In retrogradation, the polymer chains of the starch regain some of this crystallinity and in doing so force absorbed water from the gel in a process called synerisis.
To be sure gelatinization of starch is mostly irreversible, so bread once cooked stays cooked. But there is a small amount of retrogradation that can and does occur that results in the process which we call staling. In retrogradation of bread, this results in a noticeable increase in the hardness of the crumb texture.
This retrogradation or staling begins to happen the very moment that bread (any bread or cooked starch) is removed from cooking. (Now you know the reason that the Chinese food take-out rice, which was so nice in the restaurant becomes hardened bits the next day! It is the same retrogradation process.)
Refrigeration of fresh bread goods does not prevent retrogradation as most people know from experience. But, if staling has not gone too far, it is often possible to reheat in the presence of a bit of moisture and restore some of the fresh quality. But with refrigerated bread, even this restoration is fleeting.
Here is where a little knowledge of food chemistry, particularly starch chemistry, can come in handy.
If you are making your own bread at home, take the item and freeze it as rapidly as possible after it has finished cooking and it has cooled to room temperature. Freezing virtually halts retrogradation and hence staling.**
An even better method is to first freeze and then to vacuum seal (using a FoodSaver sealing and baging system) the bread or baked item. By freezing first, one does not crush the bread on vacuum sealing.
If the bread is whole, slicing it prior to freezing will facilitate its later use from the frozen state so that a few slices can be removed without thawing or struggling to cut a frozen loaf.
To use, set out as many slices as you will need and cover with a moist towel and let the slices slowly thaw and come to room temperature. You will be surprised at how short a time it takes for individual slices to thaw at room temperature. Usually in about 5-10 minutes as individual flat slices..
Or with a small potential loss in quality, one could moisten a paper towel, wrap the frozen slices individually in a moistened towel and microwave for only a few seconds, being careful not to over heat. Doing the slices individually and a few at a time avoids overheating the edges of a pack of slices in an attempt to heat the still frozen centers.
If you bring fresh bread home from the bakery, pop it into the freezer ASAP to keep it fresh. This works well with small sandwich rolls such as Italian ciabatta rolls, Mexican bolillo, telera or birote or Cuban rolls where the quality of the bread is a major part of any sandwich, hero, sub, grinder, or hoagie made from them. (And yes, you can freeze that take-home rice as well.)
However, if you wait until your bread is staling and then decide to freeze it, freezing is not going to improve the bread.
Learn more at http://www.thekitchn.com/food-science-how-bread-stales-83062
and to learn more about starch chemistry in pictorial form (PowerPoint) visit http://www.cwu.edu/~geed/440/Starches%20Megan%20Erickson.ppt
We have practiced freezing bread in our home for years for any bread that is not going to be consumed within a day or so. The downside of this is that you need enough freezer space to accommodate bread, you need to manage that which you have frozen, and you need to be proactive in freezing the bread when it is freshest.
**Freezing halts retrogradation, but if an item is held too long or under the wrong conditions, “freezer burn” can occur. Freezer burn is a freeze drying loss of moisture by sublimation from ice crystals in the food item to water vapor. This is part of the reason that rime ice forms on the inside of a package as well as on the inside of a freezer chamber as some of the rime ice moisture comes from the items as well as from repeated opening and closing of the door.
To prevent or retard freezer burn, use a vacuum sealed bag method such as the FoodSaver or other such system designed for home use. This will also prevent frozen items from picking up freezer odors and other undesirable organoleptic qualities. Just remember to freeze the bread first, then vacuum bag. Note: freezing first and then bagging works well with other crushable or soft items such as pastries, blueberries, strawberries, etc.
I have a question then. Why does placing a slice of bread in a bag of “stale” cookies make the cookies become soft again while the bread becomes stale. I always figured this was a transfer of moisture. But if bread stales from an increase in moisture this probably isn’t the case. Can you provide an explanation for this?
I should have been more clear. Bread certainly can get stale by drying out, but that’s not what happens when you put well-wrapped bread in the fridge.
Cookies? You have stale cookies? Uh-oh, someone is not paying attention, when there are cookies in the house!
The issue of staling has to do with retrogradation of cooked starch. A cookie and most cakes, while a form of bread, are usually very high in fat and oil in addition to sugar and or molasses and other ingredients. In fact the one thing that distinguishes cookies from other types of bread and cakes is the high oil and fat content of most cookies — so much so that the oil present is a major source of the cohesiveness of the cookie.
Chewy cookies are probably a bit more resistant to hardening since they depend variously on higher protein flour (e.g. bread flour), more fat, and more molasses in the basic mix. Soft cookies start with a lower protein flour (e.g. cake flour). Good old Alton Brown has a good explanation of various cookie styles: http://www.youtube.com/watch?feature=player_embedded&v=FWoN0PtsIIQ
Most likely, if you soften cookies with a piece of bread you are simply using the bread to raise the relative humidity in the closed container as you have suggested. If this be the case, then anything that acts as a source of additional moisture should also soften those hard cookies.
You might try a small clean, slightly moistened sponge, a damp tea bag, or even a damp paper towel in the closed cookie container. Take care not to let the moisture source touch the cookies. See if that works as well. If so then, the action of the bread slice is as you suggest just a source of moisture to raise the humidity.
Careful though, as moisture will hasten mold growth, You might try this in the refrigerator.
Then again if your cookies are Oreos or even my favorite, oatmeal, there is always the trusty glass of milk as a ready source of moisture.
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Really people, “where’s the science?” Look it up, do your own research. Your responding on the Internet. The info you need is at your finger-tips. Your questioning some one without doing your own due diligence. Have we become this lazy as a society? Jeeze!