June 01, 1994
by Teresa Acklin
The art of bread making has been known since 4000 B.C. The judgment as to whether bread is “good” is subjective; it is a matter for the individual baker to satisfy the demand from his market. But one factor is clear: the need to produce bread of a consistent standard and quality so the customer continues to buy it.
This need dictates consistent raw materials flour, yeast, salt and water. The same goes for many other ingredients used in a variety of recipes including fat, emulsifiers, soy flour, milk, sugar and so on.
But because flour is the major ingredient, the miller, in liaison with the baker, must do his utmost to provide consistency, day in and day out. As a comfort to the miller and the baker, the authors of Modern Cereal Chemistry state that reasonably satisfactory bread can be made in most countries from almost any type of flour, provided that suitable systems and techniques employ a “given consistency.” Because many different bread processes and recipes are used worldwide, only four will be used to illustrate techniques. The discussion will focus on yeast-raised (leavened) bread. Three of the four processes are used on an industrial or large scale. These processes are the so-called traditional straight-dough, continuous mechanical dough and the batch mechanical dough, which is better-known as the Chorleywood Bread Process. The fourth process, activated dough development, normally is used by the smaller bakery.
The flour characteristics shown in the accompanying table normally are satisfactory for each of the four white bread-making processes, but they are indicative only. Protein levels often are dictated by local wheats, so many possibilities exist, with baker adjustments carried out as necessary.
Traditional straight-dough process.
This process involves mixing flour, yeast, salt and water, plus any other desired ingredients, in bulk for up to 20 minutes. The dough in the bowl, on wheels, is put to one side, covered and allowed to ferment for three hours at 27&C.
Thereafter, the dough is mechanically divided and moulded into ball-type shapes of the desired weight, which are allowed to stand for 15 to 20 minutes. This is known as the first proof.
The process continues with remoulding into the final shaped dough piece, which is placed on a baking sheet or in a baking tin. The final proof continues for 45 minutes to one hour in a proofer (or “prover”), which is humidity controlled at up to 48&C. The dough then is baked for up to 30 minutes at 225&C in a traveling oven. The total time of this process, from flour mixing to the oven outlet, is about five hours.
The bread is cooled and then sliced and wrapped if required. Cooling on a large scale is carried out industrially over times ranging from one hour to two hours, 30 minutes or more in a large ambient air cooler, sometimes air conditioned. The interior crumb temperature is reduced ideally to 27&C or less to optimize slicing performance.
Variants include the sponge-and-dough process, which extends the processing time by two hours or more. In this method, fermentation is split into two stages: sponge and dough.
The sponge stage mixes part of the flour and water and often all of the yeast; the dough stage contains the remaining ingredients. This process, which demands strong flour, was popular in the United States, Canada and Scotland. Although supplanted by the continuous mixing process in the U.S. during the 1950s and 1960s, the sponge-and-dough method made a comeback and now ranks as the principle method of pan-bread production in the U.S. Nearly every new commercial wholesale bread plant built in North America uses sponge-and-dough methods.
The major benefit of the traditional straight-dough process one which is even more apparent with the sponge-and-dough variant is the superb organoleptic nature of the bread produced. Its taste, aroma and appearance are a class above other bread.
Frozen dough a well established product in the U.S. now emerging in Europe typically uses the straight-dough process. Frozen dough processing follows conventional methods for mixing, dividing and rounding, but dough pieces are then immediately moulded and then frozen. No fermentation time is allowed. Activated yeast can be damaged by freezing, resulting in volume and performance problems when the dough is baked off in the in-store bakery of a supermarket or at home by the consumer. Minimal in-plant processing time is, thus, essential to hold down yeast activity before freezing.
Another variation of the straight-dough process is the no-time dough method. Like the frozen dough processing, it allows almost no floor time, usually 15 minutes or less. Make up follows immediately. To adjust dough performance, the formula contains L-cysteine or other functional ingredients that condition the dough. This method tends to be used by small wholesale bakeries.
Continuous mechanical dough process.
This efficient process was an ingenious American invention dating from the mid 1950s. It is used in the U.S., although it is declining in popularity.
Baker opinion about continuous mixing is divided in part because the texture of the finished loaf crumb has an angel cake, or very even, appearance. Some consumers do not necessarily want such an even texture, because “homemade bread is not so even.” Known as the Do-Maker process, it begins with a so-called pre-ferment or brew of about three hours. This mix consists of a sugar solution with yeast and a significant portion of the total flour required.
The next step is to combine the brew with the remaining ingredients. The dough then is fed to a continuous mixer. The mixer, similar in appearance to an extruder, has two rotating impellers. Dough is pumped at a constant rate and developed.
In this process, dough temperatures are higher than those experienced with straight-dough methods. Energy input is significant, some seven to eight times that of traditional processes. The high temperatures require the use of high-slip or high melting-point fat, and oxidants such as ascorbic acid must be present.
The efficiency pay-off is in the lower total process time and reduced capital costs compared with the traditional process. After the three-hour brew, the time from brew to oven exit is about 1 hour, excluding cooling. This process is very suitable for large-scale industrial baking plants with long continuous runs on one bread type.
North American bakers learned a lot about handling liquid brews from their experience with continuous mix. Liquid sponge and liquid brew systems popular for preparing the soft buns used by fast food operations are direct descendants of the continuous mix method. These processes mix slurries of yeast, nutrients and, in the case of liquid sponges, flour. Allowed to ferment for a set period of time, the liquid brew or sponge is sent through a heat exchanger to reduce its temperature, thus temporarily shutting down yeast activity. When the mixer is ready for its next batch, the brew or sponge transfers to the mixer as a liquid to be mixed with the rest of the formula ingredients. The result is a batch of dough that is ready for conventional dividing, rounding and other downstream steps.
Batch mechanical process.
This process, often called the Chorleywood Bread Process (CBP), is another clever invention of the late 1950s-early 1960s. Developed by the British Baking Industries Research Association, it is widely used in the United Kingdom, Australia and South Africa.
CBP uses compressed yeast (or cream or liquid yeast in more recent times) and does not require a brew, as does the continuous mechanical process. According to researchers, the critical time/energy window required for ideal bread production is two to five minutes at 11 watt hours per kilogram. High slip-point fat at about 0.75% of flour weight and ascorbic acid at around 75 parts per million (ppm) also are required.
The total time from flour mixing to the final loaf, excluding cooling, is around one hour, forty-five minutes, so the system is very quick. Furthermore, because it is a batch rather than a continuous process, CBP is flexible and is capable of many alterations in bread type, formula or other changes within any 24-hour run.
Other advantages include about 4% greater water absorption because the process allows greater retention of solids normally lost in fermentation. There also is less dough softening because of the shorter time involved.
Furthermore, because there is less material in progress, spoilage during a stoppage is reduced. Staling is less rapid than traditional straight dough bread, and weaker flours can be used. Highly flexible, CBP makes doughs for all kinds of bread, including French types, and uses many different sorts of flour. Much criticism has been leveled at this process, including complaints that the product resembles “cotton wool,” is tasteless bread, sticks to the teeth, etc. The fault is not in the process but in its flexibility. Some bakers run very lean formulas, which tends to produce bread that encourages such comments.
Activated dough development process.
This is another batch process developed around 1960 which does not involve the expensive equipment required with the mechanical dough processes. Active ingredients include fast-acting L-cysteine at about 35 ppm, fat, ascorbic acid at more than 50 ppm, yeast and salt.
The mixing time for this process, about 15 to 20 minutes, is longer than the five minutes or fewer for mechanical processes. Nevertheless, the total time from flour mixing to the finished loaf is around two hours, and the process is similar in its remaining aspects to the other processes.
As with CBP, activated dough development permits the use of weaker flours, but the activated dough process is not as flexible as CBP. Still, the activated dough development process is suitable for the small baker.
It can be seen with just these four examples, not to mention the enormous number of variations used in many countries, that bread-making processes are complicated. Large-scale industrial or plant bakers always are prone to stoppages due to mechanical malfunction or ingredient failure, which leads to significant spoilage and losses. For example, just a one-hour stoppage at a large baking plant making 8,000 to 10,000 loaves per hour represents a huge revenue loss because the doughs, at whatever stage in the process, are maturing and cannot be stopped.
Further and continuing developments in the bread-making process are being made as a result of the widespread use of computers for process control.
By David Sugden, a grain industry consultant.Flour characteristics for bread processes
|*measured on a dry basis|
|**method: 7 grams/25 milliliters, including initial 60 seconds.|