Staling is a complicated process that begins shortly after baking and involves a number of physicochemical changes. These are mostly associated with an increase in crumb stiffness and moisture loss. And as a result, there is a loss of eating quality because of flavor, color, and texture deterioration. But it does not mean stale bread has already gone bad. Stale bread still safe to consume, although not as good as freshly baked bread—you would want it soft.

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Some people store bread in the refrigerator to extend its freshness. But the truth is that it only makes things worse, quality-wise. Sure, the temperature inside the refrigerator slows down the growth of microorganisms, but it also speeds up the rate of starch retrogradation, or simply staling (more on this below).

But how to properly make stale bread soft, anyway? To explain better how, a brief explanation of how bread staling occurs should help.

STALING AND RETROGADATION

Bakery products with a crust (mostly bread and cakes) tend to dry out quickly as water migrates from the crumb, resulting in a firmer and drier texture. The crust, on the other hand, tends to become rubbery or soggy. The rate at which these changes occur is determined by storage conditions, crust thickness, and the product’s crust-to-crumb ratio. For most consumers, the condition of the storage area (such as the refrigerator) is the culprit. The maximum staling rate for bread is thought to occur at refrigerated temperatures.

In baking science, these changes occur during starch retrogradation. Starch retrogradation is when starch in bread cools and reverts to a more crystalline structure. Starch granules contain polysaccharides amylose and amylopectin. Both of these may be involved in a textural shift that causes them to become more “gritty” over time. This is evident when warm starch molecules in bread cool, shrink and then firm up in the process of staling.

Starch in freshly baked good, however, is still in existence in gel form. A bread is said to be “fresh” when the starch remains as a gel. When the starch regains its crystalline structure, the product gets firmer and becomes “stale”. In science, this is referred to as starch retrogradation.

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Starch retrogradation is more likely to occur in high amylose starch. This is the same reason why long grain rice, as left over, becomes hard over time. Amylose retrogradation is nearly finished by the time the product has reached room temperature. Amylopectin retrogradation takes longer than amylose retrogradation, and is thus the principal cause of staling.

MAKING STALE BREAD SOFT

Commercial breads are able to prolong their freshness because of the additives they contain. Such ingredients bakers use include emulsifiers or bread softeners such as sodium stearoyl lactylate, monoglycerides, and calcium stearoyl lactylate. They are permitted at a QS level in all baked products, and retard retrogradation during cooling and subsequent storage by binding to the amylose fraction of the wheat starch at raised temperatures.

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Sure, commercial breads stay fresh for longer because of the ingredients they contain, but they become stale eventually. Some people would throw bread that has become stale. That is a wrong habit, though. Luckily, there are a few proven ways to revive stale bread. Here they are:

Reheating in the oven

To do this, turn on the oven and set it at 300ºF (150ºC). Reheat the bread for up to 15 minutes. This will depend on the degree of dryness and the size of the bread. The idea here is to replace the moisture that was lost. So you would want to wrap the bread first in damp towel or brush the crust with water before wrapping it in foil. The steam is retained by the wrapping as the water tries to evaporate. The bread then absorbs the steam to become noticeably softer. The big question is, is reheated bread the same as it was fresh out of the oven?

Definitely no. A freshly baked bread has a soft crumb and a crispy crust. But with a reheated bread, do not expect a crispy crumb.

And remember that the effect of this method works only for an hour or two before starch retrogadation sets in again so immediately consume your revived bread.

Steaming

The process of steaming stale bread is similar reheating in the oven. To do this, bring a pot of water to a boil in a steamer to generate steam. And then place the bread in the steamer for up to 15 minutes, but 5 minutes should usually suffice.

This method works best if the bread is very hard as this produces more moisture and less heat.

References:

W. Zhou, Y. H. Hui, I. DeLyn, M. A. Pagani, C. M. Rosell, J. Selman, N. Therdthai (2014). Bakery Products Science and Technology (2nd edition). John Wiley & Sons, Ltd

V. Vaclavik, E. Christian (2014). Essentials of Food Science (4th edition). Springer.

S. Cauvin, L. Young (1999). Technology of Breadmaking. Aspen Publication, Inc.

M. Gibson (2018). Food Science and the Culinary Arts. Academic Press

The post How To Make Stale Bread Soft? appeared first on The Food Untold.

How do you store sourdough bread? To better answer this question, a little basic bread chemistry should help.

Sourdough breads or doughs are different than typical homemade white bread. They are more tangy and flavorful because they contain an acidic component such as buttermilk, watered-down yogurt, or cultured bacterial “starters.”

Starters are a small bit of dough that was preserved from the last time you made bread. The baker adds a bit more water and flour to the starter and then lets it ferment for a longer amount of time (2-24 hours) before adding the other bread components. This replaces any added “baker’s” yeast and provides the finished product its distinct flavor. There are several sourdoughs around the world, each with its distinct “starter” and flavor.

This depends on several factors such as the combination of bacteria and yeast culture and country of origin. One common bacteria and yeast combination is Lactobacillus sanfrancisco bacteria and Saccharomyces exiguus, a non-bakers yeast. These microorganisms are important during fermentation. The bacteria consume and break down maltose sugar to produce carbon dioxide and acetic and lactic acids. The acids are responsible for the distinct sour taste of sourdough bread. The yeasts also produce bread-leavening carbon dioxide and break down the byproducts of lactic acid fermentation.

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Another characteristic of sourdough bread is the lack of the brown color for a baked product. This is because of increased acidity due to lactic acid production by bacteria and yeast. Browning reactions are slowed down by acidity.

Now that we’ve covered some of the basic things to know about sourdough bread, let’s discuss how it becomes stale and how to store it properly.

HOW SOURDOUGH BREAD STALES

It is worth noting that sourdough bread is different than regular yeast-leavened bread. It has higher hydration. Hence, it contains more moisture in the interior and a more tender and open crumb. Generally, the higher the hydration, the better. It helps delay crust forming, making the crust thinner as it forms.

The higher hydration also helps make the sourdough bread fresh for longer.

Staling starts as soon as the bread cools down after baking. It starts as the crumb begins to degrade as a result of the movement and evaporation of water. During baking, all of the water surrounding the starch travels inward. As the sourdough bread ages, the moisture evaporates, leaving a bread that is still tasty but not as fresh as the day it was baked.

Sourdough bread can be light and fluffy. However, as it ages, it becomes hard and dense. Water migration will continue until there are no more water molecules left for the reaction to occur. Bread that has gone stale will have a hard, dry surface.

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The good thing about sourdough bread is that it does not get moldy as fast as regular yeast-leavened bread. While molds love to live in damp or moist conditions, they do not prefer acidic environments, which sourdough breads are, all thanks to the good bacteria present.

But it is just one factor that preserves the freshness. Remember that sourdough breads are organic—no preservatives at all. Generally, (homemade) sourdough breads are at their peak of freshness within the first 24 hours. But it can last up to 5 days at room temperature.

To preserve sourdough breads and extends their shelf life, they should be properly stored.

METHODS OF STORING SOURDOUGH BREAD

Knowing how to store sourdough bread requires knowledge of its composition and chemistry, which we briefly discussed earlier.

There are several ways to store sourdough bread. But most of these methods have a disadvantage so these should be done properly. For example, wrapping the bread in a foil will prevent or reduce airflow, helping the bread to retain moisture for longer. But the moisture in the bread and the foil makes a great combination for molds to thrive.

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Some prefer to store bread in a paper bag. Paper bags are environmentally friendly, inexpensive, and visually appealing. They allow your bread to “breathe,” enabling moisture to escape gradually. This prevents mold to grow, and the beautiful crust to remain crisp. However, the permeability of a paper bag allows humidity to move. Thus, it will be hard for sourdough bread to maintain a soft inside.

If the bread has been sliced already, leave it on a breadboard cut-side down. This keeps the bread from drying out while preventing any moisture from accumulating on the crust.

If the bread is already on its 5th day, wrap the bread (whole or sliced) with plastic freezer wrap, sealable plastic bag or aluminum foil and store it in the freezer. If properly stored, frozen sourdough bread should maintain its quality up to 3 months. But the shorter the freezing duration, the better because the flavor diminishes over time. Once the bread is ready for use, simply take it out, thaw, and place it in a pre-heated oven.

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One common misconception about storing sourdough bread is that it is fine to store it in the refrigerator. Well, never store leftover sourdough bread in the refrigerator. When bread is refrigerated, the starch molecules in the bread recrystallize considerably more quickly than they would at room temperature. Furthermore, the inside of the refrigerator will dry the bread out.

The post How To Store Sourdough Bread? appeared first on The Food Untold.

Our ancestors enjoyed breads without leavening them. They were basically made of cooked mixture of flour and water, and often added with salt. Today, unleavened breads still do exist. However, there is no denying that people consumed more leavened baked products. The process of leavening occurs when the gluten structure or air spaces is filled with a leavening agent, making the dough or batter to rise and expand during baking. Although carbon dioxide is the primary cause of leavening, other gases, such as ammonia gas, water in the form of steam, and integrated air (added during mixing), also contribute to the expansion of baked goods.

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Leavening can be considered the key step in bread making. Without leavening agents, doughs and batters would be dense and low in volume, resulting in dense baked items. Hence, the aeration in the crumb structure greatly contributes to the sensory assessment and consumer acceptability of bread.

Leavening agents or leaveners are categorized in three forms:

1. Biological
2. Chemical
3. Physical (mechanical)

Let’s discuss each of them.

BIOLOGICAL LEAVENING AGENTS

The biological process of fermentation may produce leavening, in which the bacteria or yeast works to metabolize organic materials that are fermentable.

Bacteria

Lactobacillus sanfrancisco bacteria is an example of this. L. sanfrancisco is a lactic acid bacteria
(LABs), which are a class of gram-positive bacteria that can transform organic acids from carbohydrate sources into a wide variety of metabolites. Organic acids, such as propionic, formic, acetic, and lactic acids, make it difficult for pathogenic and spoilage microorganisms to develop.

Lactic and acetic acids are particularly important during fermentation because they are responsible for producing sourness in sourdough bread.

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Making sourdough bread require the presence of yeast and bacteria in a ratio of about 1:100. When L. sanfrancisco is used, it if often along with Saccharomyces exiguus, a non-baker’s yeast. Depending on the type of flour and the country, different lactic acid bacteria predominate in sourdoughs. Other LABs that may be used in sourdough include Lactobacillus sakei, Leuconostoc mesenteroides, Lactobacillus paracasei, Leuconostoc citreum, and Weissella cibaria.

During fermentation, the bacteria break down maltose, releasing carbon dioxide and acetic and lactic acids in the process which adds taste in the form of sourness, while the yeast produces carbon dioxide that leavens the dough. The yeast breaks down the by-products of lactic acid fermentation, but the lactic acid bacteria can break down carbohydrates that the yeast cannot.

It is usual practice to save starters or sponges of dough from one baking and utilize them in another. These starters or sponges contain both yeast and bacteria.

Yeast

Yeasts are eukaryotic, unicellular microorganisms that belong to the fungi kingdom. Yeasts can be distinguished from bacteria by having larger cells and having cell morphologies like oval, elongate, elliptical, or spherical. Typical yeast cells have a diameter of 5 to 8 μm, while some are significantly larger. Smaller cells are more common in older yeast cultures. The majority of yeasts used in food production split through budding or fission.

Saccharomyces cerevisiae is the most common strain of yeast in making bread. Since ancient times, fermented cereal-based goods have been made using S. cerevisiae. The evolution of the modern baking industry was significantly influenced by its domestication and widespread proliferation.

The Latin name, Saccharomyces cerevisiae, means brewer’s yeast. In the fermentation process that creates bread dough, yeast consumes the starch and sugar found in flour. And it transforms them into carbon dioxide and alcohol. In an anaerobic process, it releases zymase, which breaks down fermentable carbohydrates into ethanol and carbon dioxide (the amount of carbon dioxide produced increases as the number of yeast cells increases). The majority of the alcohol is then volatized in baking, and the carbon dioxide provides the leavening action.

Baker’s yeast comes in three forms: active dry, rapid-rise, and quick yeast. They are most frequently used at home. All of these forms are available in dried form, which is advantageous for home bakers as they have 1 to 2 years of shelf life in the refrigerator.

Commercial bakers frequently use fresh or wet yeast because it is more effective, but it only has a shelf life of two weeks, making it less suitable for home bakers. However, the addition of warm water or milk and the baking process provide the heat and moisture that the yeast requires to become active (for heat).

CHEMICAL LEAVENING AGENTS

Chemical leaveners are intriguing since they start working almost instantly when added to a recipe. In situations where a lengthy biological fermentation is either unfeasible, unneeded, or undesirable, chemical leaveners are substituted instead. Baking soda is a typical chemical leavening agent.

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Baking soda

It is sometimes referred to as sodium bicarbonate or bicarbonate of soda, is a “base” that easily combines with acids to produce carbon dioxide gas. The most common sources of acids added to a baking soda leavened quick bread or muffin are buttermilk or sour cream (lactic acid), molasses (acetic, propionic, and aconitic acid), lemon juice (citric acid), or cream of tartar.

Combining baking soda with an acid, and a liquid activates it. This kick starts a reaction that produces millions of tiny carbon dioxide in the batter or dough.

The acid not only aids in the production of carbon dioxide, but also works to neutralize the combination to prevent the unpleasant taste of alkalinity from lingering in the finished product (basicity). Therefore, it is important that only the exact amount of baking soda is added as specified in a recipe.

Another thing to remember when working with baking soda is that it reacts quickly with heat and carbon dioxide when incorporated alone. It may escape even before it is able to leaven the batter. Therefore, in order for baking soda to be beneficial, it must be mixed with another ingredient. To delay the carbon dioxide production and prevent it from escaping, either a liquid acid (lemon juice) or a dry acid (cream of tartar) plus liquid should be added.

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Baking powder

Baking powder is another chemical leavening agent. But unlike baking soda, baking powder is a complete leavening agent—it already contains a base and acid to do its job. To put it simply, an acid is no longer necessary because the acid is already built into the mixture. Baking powder begins to function upon contact with a liquid.

Baking powder consists of three components: sodium bicarbonate (baking soda), one or more a dry acid (such as cream of tartar), and inert cornstarch filler. Cornstarch is there as a filler to keep the dry acid and base physically separate from one another. The filler also absorbs excess moisture in the air to prevent caking and/or reduction of its potency.

There are two types of baking powder: fast or single acting powder, and slow or double-acting baking powder

Fast/single acting baking powder produces carbon dioxide as soon as water is added. Hence, a flour mixture made with it should be handled fast and correctly and placed in the oven as soon as possible. Any delay gives the carbon dioxide time to escape, reducing the mixture’s capacity to rise. For each cup of flour, about 1 1/2 to 2 tablespoons of single-acting baking powder is required.

Double-acting baking powder, on the other hand, is slow-acting. This is what most commercial bakers use in their products. Most common are sodium aluminum sulfate and phosphate powder. It releases carbon dioxide twice: first when moistened (in a mixing bowl) and second when heated (in the oven). For each cup of flour, approximately 1 to 1 1/2 teaspoon of double-acting baking powder is necessary.

Cell walls may be stretched and break if too much baking powder is added to a formulation because of an overstretched, collapsed structure and the release of carbon dioxide bubbles.

PHYSICAL (MECHANICAL) LEAVENING AGENTS

The simplest technique of leavening is physical leavening, which includes adding air to a batter or dough mechanically or physically.

Air or steam

Almost all batters and doughs contain some amount of air, which when heated expands and adds to the product’s volume. In “unleavened” baked goods, such as some breads, crackers, or pie crusts, it could be the only leavening agent.

There are several ways to incorporate air as a leavening agent during baking. Creaming sugar and fat, together can add air to a cake. Creaming incorporates air by beating sugar crystals and solid fat (usually butter) in a mixer. This occurs because sugar crystals are capable of physically dissolving through the structure of the fat. As air becomes trapped by the web of sugar and fats, air pockets are created, adding volume to the final baked product. Often, creamed mixtures are further leavened using a chemical leavener, usually baking soda.

Another way to physically leaven using air is by beating egg whites or whole eggs. This is often done when making angel food or sponge cake. Due to their ability to foam when forcefully beaten or whisked, egg whites can leaven baked goods. This is due to the egg white’s capacity to hold air, which is what gives it its function as a leavening agent. The volume of whipped egg whites can grow by up to eight times. This leavening is made possible by albumin and ovalbumin, two proteins found in egg whites. This post further explains this.

Steam

The conversion of water to steam is a physical change, thus, steam is a physical leavening agent in baking. Nearly everything is leavened to some extent by steam. Steam vapor is produced in 1,600 parts for every part of water. Water, juices, milk, or eggs are examples of liquid components that can be used to create steam. Foods such as cream puffs, choux pastry, and popovers rely on steam for leavening. The dough protein expands as a result of the creation of steam, and the egg protein denatures and coagulates to give them their distinctive high volume and hollow interior.

Sometimes steam is injected into the oven at the start of baking. This is to make sure the bread rise higher and the crust is thinner.

References:

M. Wallert, K. Colabroy, B. Kelly, J. Provost (2016). The Science of Cooking: Understanding The Biology And Chemistry Behind Food And Cooking. John Wiley & Sons, Inc..

V. Vaclavik, E. Christian (2014). Essentials of Food Science (4th edition). Springer.

M. Gibson (2018). Food Science and the Culinary Arts. Academic Press.

J. Jay, M. Loessner, D. Golden (2005). Modern Food Microbiology (7th edition). Springer.

W. Zhou, Y. H. Hui, I. DeLyn, M. A. Pagani, C. M. Rosell, J. Selman, N. Therdthai (2014). Bakery Products Science and Technology (2nd edition). John Wiley & Sons, Ltd

The post What Is A Leavening Agent In Baking? appeared first on The Food Untold.

The majority of food items have their expiration date, and bread is no exception. Like most baked products, bread is an example of semi-perishable food. It does not require refrigeration for a short while. It may last 3 to 5 days at room temperature or longer. There are several signs to tell if bread has already gone bad. Bad mold growth is usually the obvious sign that it is time to discard a loaf of bread. But how long until bread begins to mold?

Bread takes 5 days or so until it begins to mold. This depends on several factors such as the storage conditions. Is it humid and warm? Bread can last up to 5 days more in the refrigerator. But this is not ideal (unless you are making breadcrumbs) because the temperature is harsh for the starch molecules. Starch molecules are made up of long chains that shorten and firm up when they cool, a process known as staling. This is visible when stale products become softer when heated and firm up again after cooling.

Another factor is the ingredients of the bread. Usually, homemade bread grows mold much quicker than store-bought. This is because store-bought bread typically contains many preservatives that extends shelf life. Examples of these include potassium sorbate, sorbic acid, and sodium benzoate.

WHY MOLDS GROW ON BREAD?

Mold growth is the most common cause of microbiological spoilage in bread. They are fungi that grow in the form of multicellular filamentous structures known as hyphae, which helps absorb and break down nutrients. Molds present on bread are usually off-white, and sometimes with fuzzy black, green, or pink spots.

Because molds and mold spores are thermally inactivated during the baking process, bread straight out of the oven is mold-free. Molds reproduce through spore. Mold spores are tiny invisible to the naked eye. And you may not realize it, but mold spores are virtually everywhere— in your kitchen and even inside bakeries.

Sure, bakeries can be as hygienic as possible, but the environment is not sterile because of the ingredients used for baking. Dry ingredients, specifically flour, contain mold spores, and flour dust spreads easily through the atmosphere. Just a gram of flour can contain as many as 8000 mold spores. Mold spores present in the atmosphere during chilling, slicing, packaging, and storage contaminate bread after baking.

But mold spores are just one of the requirements in order for molds to grow. The appropriate temperature, moisture, and food (bread) must also be available, all of which can be easily sourced in a piece of bread at room temperature. This is why molds do not grow if the bread crust is rather dry and the relative humidity of the atmosphere is below 90%. Molds will grow quickly in a damp environment, especially on a loaf within a wrapper. This is especially true if the bread is wrapped while still hot from the oven, causing droplets of water to condense on the inside surface of the wrapper.

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When bread is cut, the interior, which is more vulnerable becomes infected with mold. The moist, cut surfaces of sliced, wrapped bread are a great substrate for molds to develop on. Furthermore, the packaging prevents moisture to escape.

CAN YOU EAT MOLDY BREAD?

Some people have tried removing the moldy portion of a bread, and got away with it. But this is totally not recommended.

There are more than 10,000 different types of molds. In bread spoilage, the 5 most common types responsible are Aspergillus, Fusarium, Mucor, Penicillium, and Rhizopus. Rhizopus (nigricans) Stolonifer is the most frequent type of black bread mold. It has a fluffy look due to the presence of white cottony mycelium and black sporangia.

As earlier mentioned, (storage) temperature has an effect on the growth of mold in bread. This also affects the type of mold that would grow. Neurospora sitophila, a reddish mold, grows in bread that has been stored at high humidity or wrapped while still warm. In tropical countries, such as India, Aspergillus spp is the dominant spoilage mold. Penicillium spp. is usually blue or green, flat and spreads slowly.

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Aside from spoilage, some molds pose a serious threat to public health because they can produce mycotoxins. Mycotoxins are secondary metabolites that are toxic that, when ingested may cause illness or death.They are extremely resistant and can withstand the heating method used to eliminate molds. While directly eating mold-contaminated bread may lead to exposure to mycotoxins, consuming the products of animals fed contaminated bread may also result indirectly in mycotoxin exposure.

The truth is that eating a moldy bread may be poisonous if sufficient amount of mycotoxins is present. And discomforts vary depending on the quantity of toxin ingested, the length of exposure and the age and health condition of the person. In some animals, bread molds are highly toxic. According to studies, 10% of Aspergillus spp. and Penicillium spp. are harmful to mice.

Today, consumers are more likely to reject the entire loaf than to cut away the clearly moldy section and eat the rest, as was once typical in the past. And since it requires a considerable quantity of mold growth to form mycotoxins, molds and mycotoxins pose little harm to public health in developed and developing countries

PREVENTING MOLD GROWTH

Proper storage is the key to prevent mold growth and extend the shelf life of bread. The idea is to keep the bread from being exposed to what molds require to grow: moisture, temperature (warmth), and light. This is especially true if your home is warm and humid. Ideally, you should have a cool, dark, and dry place to store bread. If not, there are several containers that work very well in keeping bread fresh for several days.

Brown paper bag

First is brown paper bag. This is the container most bakeries used for their products, and for a good reason. Paper bag prevents bread from going moldy because of its permeability—it allows moisture to escape. This is why it works great for breads with a hard crust. While closed allows air to circulate inside the bag, helping maintain the crusty crust and moisture in the crumb.

One problem with paper bag is that it makes bread to go stale much quicker. For this reason, bread in a paper bag should be consumed within 2 to 3 days before it becomes stale.

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Linen bag/ cloth bread bag

If you do not have a brown paper bag, another great option is a linen bag or cloth bread bag. It helps prevent mold growth in a similar way. Just like a paper bag, a linen bag is made of a material that allows the content to be breathable. It allows moisture to circulate to keep the bread crusty and fresh for 2 to 3 days.

Bread box

A bread box is great because it keeps bread crust crunchy, while keeping the center soft and chewy. Its inside is dark and dry, and the small holes provide a good balance of moisture and enough ventilation. Bread boxes are mainly used to store bread and keep them fresh for a few days. To prevent mold growth, ensure there is ample room for good ventilation. To make sure of this, do not overload the bread box. Doing so will lead to an increase in humidity. Or better yet, use a bigger bread box.

If you do not have a bread box, a kitchen cabinet will do. A kitchen cabinet should provide proper air circulation to prevent mold growth. Just make sure to place the bread first in a linen bag or an open plastic bag.

The post How Long Until Bread Begins To Mold? appeared first on The Food Untold.

A long time ago, unleavened bread was more common. Unleavened bread is bread prepared without the using of any rising agents, such as yeast or soda. During the ancient times, bread making involved mixing crushed grains and water, and then baking the mixture under the sun. And then the Egyptians changed the baking world for the better when they incorporated yeast in the dough. Our ancestors have used yeast, long before writing was invented. But it was only around the 1000 B.C. when the first yeast-leavened bread was baked in Egypt. Egyptians allowed a batch of dough to stand. The semi-domesticated yeast cells grew, allowing carbon dioxide (CO₂) to form and make the dough rise. The bread leaved by yeast was soft and taste better. Since then, leavened bread became a staple. Although unleavened breads in many forms are still popular today.

But how exactly bread rise? And why your bread is not rising?

THE SCIENCE OF RISING BREAD

As we already know, the difference of leavened bread and unleavened is the addition of a rising or leavening agent—commonly yeast. Flour comes from wheat or other forms of grains that contain the proteins glutenin and gliadin. When the flour is mixed with water, the two proteins react to form a loose network of gluten. To better picture how gluten looks like, think of it as a net that holds the entire structure of bread.

Without water, gluten does not form, and more of it is formed when more dough is mixed. Furthermore, kneading the dough makes the gluten network stronger. In addition to this, tiny bubbles are incorporated that get trapped in the gluten. After kneading, the dough is allowed to stand and ferment.

During fermentation, the yeast produces enzymes that convert maltose into glucose, a simple sugar. This glucose is what the yeasts use for energy. In return, they produce carbon dioxide, the gas that enlarges air bubbles, making the dough to rise.

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During baking, the gluten proteins denature because of the high temperature. This forms intermolecular and disulfide bond interaction. From here, the starch and protein network tightens and strengthens, and the gas bubbles run out of room to expand. As the gas bubbles try to expand until they burst, pressure increases, transforming the loaf’s structure from a network of separate gas bubbles to an open, porous network.

The starch continues to solidify and gel like shape during the last stages of baking. The starch granules, on the other hand, continue to firm up after baking and chilling, making the bread easier to slice when cool.

MAKING SURE BREAD IS RISING

Wondering why your bread is not rising at all? There are several reasons why.

Gluten

Gluten formation is one of the first reasons why baked products rise properly. We said earlier that gluten acts as a net that holds the bread together. During dough rising, gluten traps the gas bubbles as fermentation progresses. But if the gluten network is weak or not sufficiently developed, the CO₂ may just easily escaped, making it unavailable for leavening. But how do you tell the gluten network has developed? A properly kneaded dough should be elastic, holding its shape well, and springs back when poked.

In batters and dough, carbon dioxide is a primary leavening agent. The amount of flour needed in a recipe is related to the amount of flour used. For example, a high-flour (dough) formulation requires more CO₂ production for leavening than a high-liquid (batter) one. As a result, the recipe must contain more of the CO₂-forming ingredient.

Sugar and salt

In some recipes, a small amount of sugar is helpful. Sugar in significantly large amount (greater than 10% by weight) dehydrates yeast cells by osmotic effect and reduce dough volume. But this is not always the case since only yeast cells are affected by dehydration of sugar. High levels of sugar are more tolerated for baked goods, including cakes, that are leavened chemically (baking soda and baking powder.)

Further reading: Food Science: The Roles of Sugar In Food

Another ingredient that must not be overlooked is salt. In baking, it has several functions aside from enhancing flavor. Another is that it controls fermentation. Like sugar, it has a dehydrating effect to yeast cells. It also competes with other ingredients for water absorption. The presence of salt will result in less water for gluten formation and starch gelatinization. However, without salt, there will be rapid yeast movement and rapid rising. The overproduction of yeast produces a collapsible and porous structure. And overstretching results in gluten strands that break.

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Yeast

Saccharomyces cerevisiae is the most common strain of yeast used as leavening agent. This strain does its job by releasing zymase enzyme, which metabolizes sugars to produce ethanol and CO₂.

Like other living microorganisms, yeasts require certain living conditions to be active. If you have dry yeasts that have been kept for years, check if it is active. Dry yeasts (active and instant) have a shelf life of 1 to 2 years. Check the label for the shelf life. Over time, yeasts lose their potency, and their ability to create bubbles in the dough is affected.

It is better to check if the yeast is active to make sure the dough rises. To do this, prepare a glass of lukewarm water and add the yeast. Then wait 10 to 15 minutes for the water bubbles to start and form on the surface. Try adding a teaspoon of sugar. Yeasts love sugar!

If there is no activity, the yeast is likely dead.

Because yeasts are living microorganisms, it is sometimes a task making bread rise. With the advent of chemical leavening agents, including baking soda and baking powder, it has become easier to bake at home. One advantage of these over yeasts is that they do not require additional time for rising. However, they are sometimes confusing to use, especially for first time bakers.

If using baking soda alone as a leavening agent, it must be partnered with another ingredient, an acid, to make it work. This ingredient can be a dry acid like cream of tartar or a liquid acid like buttermilk, citrus juice., honey, molasses, and applesauce. Baking soda is an alkaline, and in order to work, it must rely on acid included in the recipe.

The reaction between baking soda and the acid creates CO₂, forming bubbles within the dough or batter. To use baking soda, 1/4 teaspoon per 1 cup flour should do the work. Too little baking soda will not make the dough rise appropriately. However, too much baking soda will make the bubbles bigger. These bubbles will only end up joining together. And when they rise to the top, the dough will burst, resulting in a flat product. Furthermore, the excess baking soda will no longer be neutralized by the acid. The result is metallic-tasting and coarse-crumb bread.

Baking powder is no different to baking soda. It contains sodium bicarbonate (baking soda), cornstarch and a dry acid (cream of tartar). The cornstarch is there to prevent premature production of CO₂ during storage. Commercial baking powder must include at least 12 percent CO₂ gas by weight (per 100 g of baking powder must contain 12 g of CO2), while home-use powders must have 14 percent CO₂.

Baking powder starts its work when it becomes wet. This activates the dry acid to come into contact with baking soda, creating CO₂. Bakers use baking powder rather than baking soda when the batter lacks natural acidity.

References:

V. Vaclavik, E. Christian (2014). Essentials of Food Science (4th edition). Springer.

M. Wallert, K. Colabroy, B. Kelly, J. Provost (2016). The Science of Cooking: Understanding The Biology And Chemistry Behind Food And Cooking. John Wiley & Sons, Inc..

M. Gibson (2018). Food Science And The Culinary Arts. Academic Press.

G. Crosby, America’s Test Kitchen. (2012). The Science of Good Cooking: Master 50 Simple Concepts to Enjoy a Lifetime of Success in the Kitchen. America’s Test Kitchen

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