What is Crumb Softness?
Crumb softness is how the inside of bread feels when you bite it or press it. The crumb is the inside of the bread beyond the crust. The softness of the crumb is a result of the order of all the steps of mixing, fermenting, proofing, and baking. A crumb with softness has a fine and flexible texture that feels moist and not hard, dry or tough. Bread that has good crumb softness is easy to chew and keeps people enjoying it even hours after baking.
Crumb softness is a result of the interaction of many factors. These include the type of flour, the sugar and fat content, hydration level and the conditions of baking. A higher level of hydration results in a crumb which is softer and moister. Sugar and fat can also result in a soft crumb as they limit the formation of gluten. Perfect fermentation is also important in the formation of an optimal crumb structure. The final texture of the bread is a result of protein setting and gelatinization of the starch in baking. Bread that is over baked results in a dry, hard crumb. In the baking industry, the use of enzymes and dough conditioners also helps in achieving optimal softness and reduces the speed at which bread stales.
Many customers expect a certain softness in products like sandwich bread and sweet pastries. Evaluating crumb softness in a factory setting can include texture analysis, compression studies, measuring moisture content, and sensory assessment. There are several aspects that can be controlled within a flour mill or bakery to achieve consistent softness, such as flour quality, dough formulation, hydration, fermentation, and the optimal temperatures for baking. Softness in bread crumb should be maintained by proper packaging, as it is also affected by the loss of moisture. Stale crumb detracts from the overall texture, freshness, eating quality, and can be perceived negatively by customers. Crumb softness is a primary attribute that defines bread quality.
Relationship Between Crumb Softness and Shelf Life
Shelf life refers to the time a bakery product retains texture, flavor, appearance, and safety in the given storage environment. For many baked products, microbiological spoilage is not the only factor limiting shelf life. In fact, loss of crumb softness and freshness can occur before a baked product becomes microbiologically unsafe.
After baking, bread starts undergoing physical and chemical changes. During cooling, moisture migrates from the bread crumb, and moisture is lost to the surrounding environment. During baking, starch molecules are disrupted and start to reorganize during the storage of bread. This is what is generally understood as starch retrogradation. Firming of crumb softness is therefore a continuous process even in the absence of moisture loss.
The objective of a good shelf-life strategy is to control and slow down the changes of bread and maintain the crumb softness. Achieving extremely soft bread post-baking is not the goal. Rather, maintaining softness for days or weeks is the goal, depending on the packaging system and the product.
Selection of Quality Flour
Crumb softness is a function of the quality of flour used. Different flours of different origins have different proteins, glutens, starches, moisture content, damaged starch, etc. The right flour for the right bread type is a function of the other factors that we have listed.
If not modified, very strong flour can result in over-hardness and a loss of tenderness. Weak flour creates poor gas retention and makes dough weak and results in a lost volume, compact crumb, and low-quality product. Balanced flours aid in maintaining tenderness while still contributing the necessary structure.
The size of the flour particles affects the hydration and the development of the dough. Damaged starch affects water absorption and impacts crumb softness. Flour that is of inconsistent quality results in variations in the handling of the dough and the texture and size of the crumb and the volume of the loaf from one batch to the next.
For commercial purposes, flour should be subjected to the quality-control tests that are appropriate. Moisture level, protein level, ash, falling number, water absorption, gluten, level and characteristics, and baking performance should all be determined. With flour of consistent quality, we can reliably control tenderness and crumb softness and prolong the shelf life.
Optimizing Dough Hydration
Water is integral in achieving a soft and moist crumb softness. The mixing process allows proteins and starch to absorb water and develop a structure that is necessary in the dough. During baking, water aids in achieving the desired crumb texture by participating in the starch gelatinization process.
Within an adequate range of hydration, an increase in hydration can improve the crumb softness and moisture of the crumb. However, the correct amount of hydration is context-dependent and is a function of the specific flour, the type of product, the mixing technology, and the processing conditions. There are a variety of negative consequences that arise from adding too much water. These include high moisture bread, sticky dough, and an unstable, open, and irregular crumb. Insufficient water yields a dry and dense bread.
Water Absorption
The absolute optimal amount of hydration should be determined rather than the most. Along with the absorption of flour, the bakery should consider water contribution of all the ingredients. It is also imperative to note that the mixing conditions and the temperature of the dough should remain constant as they affect the distribution of water within the dough.
Gluten and Gas Retention
Gluten formation and gas retention should be considered along the crumb softness and structure. During proofing, hydrated proteins form a matrix that enables the dough to resist the expansion of the trapped gases.
Irregular cell pattern and poor gas retention results in a firm textured bread with a smaller volume. Excessive mixing causes firm textured bread with poor gas retention.
The aim should be moderation in mixing with a goal of high gluten formation and gas retention. The strength and nature of the flour employed should be the main indicators of mixing time. Other indicators of good quality control may be employed.
Gluten formation should be adequate to allow optimal cell formation during proofing to facilitate a soft texture.
Fat and Oil
Vegetable oils, shortening, butter, and bakery fats are examples of fats and oils that enhance the tenderness and mouthfeel of bread. These ingredients improve tenderness when incorporated in the formulation of soft bread.
Fat can reduce the friction of gluten strands and create a lubricating effect in the crumb. Fat, at moderate levels, can also improve the perceived softness of baked goods during chewing. In some formulations, fat can provide moisture to the baked good and improve texture over time.
The level and type of fat used should be determined by the product. Using too much fat can negatively affect the structure of the product by affecting dough development. With a proper balance, other aspects of the product, like softness, can be improved without a negative effect on volume, ease of production, or flavor.
Control of Sugar Levels
Sugar, by interacting with water, helps to create crumb softness. As sugar is a hygroscopic substance, it can help retain moisture within the crumb which can help bread stay soft during storage.
Of greater importance is the fact that sugar, like water, is needed for protein and starch hydration and therefore, a negative impact on gluten development. Sugar, therefore, gives sweet breads and buns a soft texture.
With this in mind, using sugar in large quantities should not be considered a primary approach to increasing the shelf life of bread. Negative effects like slower yeast activity, increased browning, poor dough development, altered conditions of the product, and unsatisfactory results are some of the undesirable consequences of increasing sugar. Sugar levels must be set within practical boundaries.
Using Emulsifiers
Emulsifiers are essential in many commercial bread formulations. They improve the stability of dough, gas retention, and crumb softness as well as structure. Some emulsifiers interact and cross link with starch and gluten, forming a more even and fine crumb texture.
A well formulated emulsifier can improve the storage freshness by slowing up the rate at which the crumb becomes firm and improves the texture of the bread.
The selection of the emulsifier and the dosage used have to be calculated according to the product regulations. Excessive use of an emulsifier may result in the formation of an undesired texture and other undesired product characteristics, thus careful formulation is very important.
Using Enzymes to Delay Staling
Staling is one of the major limitations of bread shelf life. It can be delayed by the appropriate selection and use of amylase. Amylase has the ability to control starch crystallization.
During baking, starch gets gelatinized, and during storage, starch gets retrograded and contributes to firming of bread. Starch components also undergo undesired textural changes during firming, and appropriate enzyme systems can delay these firming changes.
The enzymes used have to be selected very carefully, as different enzymes may have different effects. Excessive enzyme activity may lead to a sticky or gummy crumb. Therefore, the effects should be evaluated over the intended shelf-life through controlled baking trials.
Optimizing Fermentation
Fermentation of dough plays a large role in the texture and crumb softness. Fermentable sugars are converted into carbon dioxide gas and other fermentation products by the yeast.
Doughs that are under-fermented may result in bread with low volume and a dense crumb, and doughs that are over-fermented may result in bread with poor volume and a weak structure that cannot hold the gas. Both effects may result in a poor quality crumb.
For consistency, it is important to control fermentation time and temperature. The dough and yeast need to be at a specific temperature during the right mixing and proofing times to produce predictable crumb softness.
Controlled Proofing
Proofing is a final stage of dough development before baking. This stage allows gas cells to expand within the dough and helps the dough develop its final internal structure.
Dough that is under-proofed will result in a dense, uneven crumb. On the other hand, dough that is over-proofed will result in a bread with low volume and a dense, uneven crust.
The temperature and humidity of the environment during proofing also plays a role in the final structure of proofed bread. If the dough surface becomes too dry, the proof will not be able to expand the dough to its maximum potential.
Baking
Baking is the final process which sets the internal structure of the proofed bread. As dough is heated, the yeast is indirectly stimulated and the moisture begins to evaporate. The dough is baked until it is set enough to prevent the crumb from sticking to the fingers.
Over-baked bread tends to become dry because the moisture it contained during baking evaporates. On the other hand, under-baked bread does not set the crumb softness, leaving the bread a they moist which causes the bread to become sticky.
Preventing Starch Retrogradation
One of the main reasons for crumb firming during the storage of bread is starch retrogradation. The process of ordering starts after the process of baking and cooling of bread. Gelatinized starch starts coming together to form ordered structures.
The speed of retrogradation can be influenced by formulation as well as processing. Certain emulsifiers, fats, enzymes, and other functional ingredients can help modify retrogradation. Starch retrogradation can be controlled by proper moisture management and storage.
Studying the behavior of starches is vital for many long-shelf-life bread products because these products may remain safe for consumption due to their low levels of microorganisms, despite becoming increasingly firm as a result of physical changes.
Managing Storage Temperature
The staling of bread is reversible in the presence of moisture, but irreversible when stored at a temperature higher than its glass transition temperature. In too rapid of a rate, bread can lose its texture.
Although the refrigeration of bread delays staling and helps maintain crumb softness, most bread, when refrigerated, will rapidly lose softness due to starch retrogradation. Storage temperature requirements vary for each product and should be evaluated for food safety.
For most packaged bread, a room temperature storage environment is preferred for controlling the texture.
Controlling Water Activity
Water activity describes the amount of moisture available for chemical reactions and microbial growth, and is different from total moisture content. Since physical quality and microbiological stability determine shelf life, managing water activity is necessary.
A bread product needs an appropriate amount of moisture to retain softness, but must avoid unnecessarily providing conditions for microbial growth. This can be accomplished by formulation and baking, and can be complemented by cooling, the application of preservatives where appropriate, and packaging.
Water activity measurement can be useful in quality control of long-shelf life bread products.
Preventing Mold Growth
Although crumb softness firming is a prominent cause of bread quality loss, mold growth is the primary limitation to shelf life. A product that remains soft but has mold growth is unacceptable.
Mold prevention requires good manufacturing practices, hygienic handling, suitable baking, appropriate cooling, effective packaging, and controlled storage. Where applicable, certain preservatives or preservation systems may be used.
It is important to appreciate that increasing crumb softness does not provide extended microbiological shelf life. Achieving both textural quality and microbiological stability requires an effective formulation.
Achieving Softness in Breads through Recipe Balancing
The various components of a successful soft-bread formulation (flour, water, yeast, salt, sugar, fat, functions) balance one another. Adding any component in increasing quantity may lead to formulation problems.
Increasing the quantity of water in the formulation may lead to loss of dough structure due to low flour strength. Increasing fat may increase dough tenderness, but may decrease gluten formation in the dough. Increasing sugar in the formulation may result in moisture retention by the dough, but may negatively affect the fermentation process. Increasing the quantity of enzymes may slow down the firming process of the dough, but if the quantity is too much, it may result in dough gumminess. Therefore, while developing a recipe, the entire system must be taken into consideration rather than focusing on a single ingredient.
Monitoring Crumb Softness During Shelf-Life Testing
A bakery can’t assess softness after just one bake. Thought must be given to crumbs being tested at various stages of the trial.
Considering this example, samples are tested on the day of production and after a period of time being stored. Factors such as firmness, moisture, activity, volume, sensory softness, elasticity, and visual crumb structure can be measured.
Crumb softness can be assessed by instrumental texture analysis. Sensory testing can be employed to gain a better understanding of the firmness of the crumb. Sensory assessment is conducted by a researcher or members of the public.
Considering the actual conditions of packaging and storage will yield more realistic results.
Common Causes of Hard or Firm Crumb
There are multiple production issues that can cause crumb softness. These issues include poor gluten development, inadequate proofing, insufficient fermentation, excessive moisture loss during baking, underbaking, unsuitable flour, overbaking, poor gluten development, unsuitable formulation, excessive starch retrogradation, inadequate fat and emulsifier systems, poor dough hydration and later firming due to prolonged storage.
Firming could be caused by multiple variables in production, and it is essential to evaluate quality control records to determine the cause.
Incidences of firm crumb should be investigated by ensuring an analysis of all variables including flour, formulation, processing, and storage, as well as gluten, proofing, cooling, and baking.
Developing a systematic approach to quality control and shelf life testing is the best way for commercial bakeries and mills to ensure quality products for their clients. A systematic approach to the study of crumb firmness, moisture, w/a ratio, loaf volume, and general acceptance deterioration during storage used with quality control testing can be used to improve the process. By controlling texture and microbiological stability manufacturers are also able to control the consumer perception of product freshness.