Mixing dough for bread dates back thousands of years, but the research community still strives to perfect the process in order to improve efficiencies, increase output, decrease energy usage and save money.

“When bakers mix dough for breads and rolls, there are three overall objectives,” says Kirk O’Donnell, vice president of education, AIB International, Manhattan, Kan. “There must be uniform incorporation of ingredients, proper hydration of dry components (fl ours and grains hydrate more slowly than sugar) and the development of gluten.

“If all of the ingredients are placed in the mixer at one time, the uniform incorporation of ingredients is never a problem for bread and roll dough. However, at times certain ingredients are delayed, and when this occurs, incorporation of ingredients may pose some challenges.”

CALLING THE TIME AND TEMP.

Bakers may elect to delay a portion of the water, salt, yeast and all or part of the shortening or other inclusions.

Water temperature is important to the mixture, as it controls the ultimate temperature of the dough. Most commercial bakers use jacketed mixers that circulate some refrigerant, such as glycol, as near to the dough as possible to regulate the temperature of the dough. At times, ice is used. In any case, the desired dough temperature at the end of mixing, the temperature of the added water, the amount of water in the formula (based on bakers’ percentage), the temperature of the mixing room and the temperature of the fl our all must be factored in when creating dough. The friction factor, or the amount of heat created by the mixing process, needs to be determined. The friction factor varies from mixer to mixer and with differing mixing times. The friction factor must be re-established when any parameters of the process are changed. Water acts as a lubricant in the dough and can reduce the friction required to develop gluten. It may be necessary to add water in increments to ensure gluten is formed before all the water is added.

This is why there is sometimes a delay in adding shortening to the mix. Formulas that require shortening totaling more than five percent of the fl our weight should specify that any shortening exceeding that threshold be delayed.

By incorporating salt into the dough later in the mix, bakers can reduce the energy output needed to make the dough. Salt will toughen the gluten, O’Donnell says, “and more mechanical (mixing) time will be needed to develop the gluten. If salt is added later, mixing time can be reduced by 10 to 15 percent, and the frictional heat can be reduced. Salt must also never come in direct contact with yeast, as osmotic pressure will dehydrate the yeast cells and kill them. Bakers sometimes delay the yeast, especially if they are using instant yeast. THe only reason for this is that the instant yeast should not come in direct contact with ice, very cold water or refrigerated surfaces of mixers.”

Proper hydration is essential for good-quality finished products. Sugar hydrates faster than fl our and whole wheat, while whole grain ingredients hydrate slower than white fl our. Bakers must adjust formulas to incorporate these varying parameters. Slower mixing speeds promote hydration, while faster mixing speeds promote gluten development.

GLUTEN DEVELOPMENT

“The last mixing objective for bread and roll doughs is the need to develop the gluten. Wheat as a grain has a unique ability to form a gluten network, which occurs when fl our is combined with water and energy,” O’Donnell says. The USDA’s Agriculture Research Service (ARS) has isolated wheat proteins other than gluten that also affect the mixing process. Gliaden, glutenin and the water-soluble protein albumin have been found to be as essential in forming a good loaf of bread as gluten. The time needed to develop gluten is determined not only by the amount of protein in the fl our (strength of the fl our), but also by the speed of the mixer. The faster the mixer, the less time it takes.

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“The gluten network gives the dough extensibility or plasticity, as well as elasticity. The elasticity gives the dough the necessary gas retention to achieve desired product volume and texture. If the dough is not properly developed, it may tear when sheeted. If it is over-developed, the dough will be sticky and lack gas retention,” O’Donnell says. “Bakers normally judge gluten development by checking for a gluten film or window, which is an ability to stretch the dough between your hands to form a transparent film. Some products need more gluten development (such as white bread and buns), while others need less (such as pizza).” AIB says gluten development ultimately is judged by the quality of the finished product. If the product is too fl at and low in volume, then it most likely has excess of gluten development. If it lacks symmetry, it likely lacks gluten development.

EMULSIFIERS AT WORK

The addition of emulsifiers in bread doughs does not affect mixing times, but emulsifiers can increase shelf life as well as volume. It is common to use a combination of emulsifiers and vegetable oil to replace solid shortening. Bakers often use ascorbic acid to strengthen the dough. However, because ascorbic acid will cause the dough to be more elastic, bakers should slightly increase mixing times to properly develop the gluten. Reducing agents such as L-cysteine have the opposite effect, and so bakers should reduce mixing times when these additives are used.

“Bakers most always delay the addition of fruits, such as raisins, craisins, and blueberries. This is done in order to preserve the integrity of the fruit. It is somewhat challenging to properly incorporate fruit in a dough without damaging any of the fruit,” O’Donnell says. “If the fruit is damaged, not only is the dough and resulting bread unsightly, but the sugar within the fruit that is now liberated to the dough will slow the yeast due to excessive osmotic pressure. This will cause the dough to rise too slowly or not rise at all.”

EQUIPMENT TECHNOLOGY

Horizontal mixers are most common in volume bakeries. These doughs are usually mixed in batches. Continuous mixing, where the mixers are designed to be fed by the ingredients or ferments at a pre-determined rate, while the dough is discharged at a pre-determined rate, was very common 40 to 50 years ago. But most bakers abandoned this in the 1970s because the bread lacked sufficient structure (or crumb strength). Today there are newer technologies of continuous mixers as well as batch mixers with “smart” technology that can measure gluten development in real time and compare the profile with a standard profile. AIB has worked with NIR (near-infrared) technology to measure the impact of various ingredients on mixing profiles. It is now possible to determine within two minutes if a specific ingredient has been forgotten in the batch.

Research continues to improve the baking process through automation and ingredient development. Bakers will continue to develop their craft, and technology will enable them to do it with efficiency and economy.