When a system, such as fermentation, involves many variables — not only in the type of equipment and process used, but also the choice of ingredients — then it has a fairly high degree of complexity. Factors influencing the choice of variable vary extensively, from the size of the bakery to the nature of finished products to the cost involved.

Since yeast, a living organism, is the catalyst that drives fermentation, proper controls must be put in place to regulate its activity. If not controlled, environmental factors can influence yeast's activity, causing wide variations to finished product quality that force operators to constantly fluctuate process parameters, such as mix time and oven temperature. Although yeast contributes to flavor, a lot of other organisms do as well. Sourdough, in particular, derives flavor from bacteria found in the environment.

Reactions that occur during fermentation result in improved dough handling and gas retention, as well as a range of important finished product qualities, including desirable texture, cell structure, extended shelf life and flavor. As such, bakers must carefully consider each parameter involved, how these parameters will be controlled and monitored, and most importantly, desired finished product characteristics, when designing fermentation systems for their plants.

Methodology

Fermentation can be accomplished in several ways, including the straight dough method, where all ingredients, including the yeast, are mixed at one time; a sponge dough, where about 60 percent to 80 percent of the flour is mixed with yeast and water; or a liquid ferment, or brew, which contains about 30 percent to 40 percent flour content. Straight doughs are not commonly used in commercial baking.

Liquid ferments are used more typically for bun or white bread production in this country, notes Ron Zelch, manager, product development, Caravan Ingredients, Lenexa, Kan. Fermentation times for liquid ferments range from 45 to 90 min. for lower flour, and 60 to 90 min. for higher flour ferments; whereas, fermentation times for sponge and doughs typically would run 3 to 4 ½ hr., adds Zelch. Typically, the higher the percentage of flour used, the shorter the mix times, the better the flavor, shelf life and quality.

Bakers differ in opinions regarding the ideal fermentation time for proper bacterial activity, based on individual experiences and expectations for finished product texture and flavor. Richer fermented products, such as sourdough or artisan breads, require longer fermentation times that may vary from 8 to 18 hr. For longer fermentation processes, it is very important to introduce a new starter culture to each new batch and/or use 10 percent to 20 percent of the last fermentation batch for the next batch, notes Rod Harris, Northeast sales manager, Reimelt Corp., Odessa, Fla.

In fermentation, you can create any number of bread types and flavors. The two most prominent are “sponge and dough” and “sourdough.” In sourdough creation, the fermented portion of the dough that is added to a new batch is called the mother dough, and is affectionately known in the industry as “feeding the beast,” says Doug Jump, marketing manager, Puratos, Cherry Hill, N.J. More flour and water are added to the mother dough to keep it viable. Use of mother doughs for fermentation is more common in small wholesale or retail bakeries.

Fermentation systems are available as batch or continuous processes. “There are several versions of continuous processes using horizontal or vertical tanks. Unfortunately, many years ago, attempts at continuous fermentation used horizontal tanks that were difficult to clean and could not guarantee a first-in/first-out, or mass-flow design from the tanks. These attempts gave a bad reputation to continuous fermentation systems,” Harris explains.

“Nowadays, a continuous system using vertical tanks has proven effective. A batch process may allow more flexibility in terms of cleanability and different ferment times for different products. However, batch fermentation systems must be designed with larger pumping systems including heat exchangers versus those used for a continuous system, to keep up with usage rates,” Harris adds.

Gaining control

Several environmental factors, such as temperature, pH, salt, sugar, flour, quantity of yeast and specific yeast strain influence yeast activity and can therefore be manipulated to control the rate of fermentation.

“If you have more than 1 percent salt, it will really restrict your yeast activity,” says Christophe Dewilde, brand manager, Puratos. “Each percent increase beyond 1 percent will reduce the amount of CO₂ or gas that yeast is meant to produce by 25 percent. For sugar, 3 percent to 4 percent will increase the rate of fermentation. When sugar exceeds 4 percent, it will slow down fermentation because that is the yeast's food.”

A lower temperature will slow yeast activity, optimal temperature is 95°F (35°C), and temperatures above 126°F (52°C) will kill the yeast, notes Dewilde. Bacterial activity slows down drastically below 40°F (4°C). As such, the batch or continuous stream must be cooled once it reaches its ideal fermentation time.

A fermentation system may be equipped with a jacketed and insulated fermentation tank that can be cooled and used directly; otherwise, the fermented batch must be transferred, via a heat exchanger, to a jacketed and insulated cold holding tank, Harris notes. Short-time fermentation batches that take 3 hr. or less typically use a heat exchanger and holding tank system. Longer fermentation can use the same fermentation tank for cooling, as long as the batch is used within 6 to 12 hr.; however, this technique may not effectively lower the temperature below 40°F to 45°F within the requisite time.

“All bakeries are pretty much run by time and temperature control,” Zelch says. “Smaller bakeries can fluctuate their time better than a large commercial bakery. If you're off a couple of degrees, that could really play havoc with the degree of fermentation that you accomplish. Bakers may use pH and titratable acidity (TTA) to monitor fermentation. By monitoring these parameters, a baker would be alerted when something is wrong, instead of waiting for the finished product. For instance, a baker discovered a problem with one of his ingredients when a pH reading on his ferment was tremendously alkaline, which slowed the rate of fermentation. After testing all of his ingredients, he found the salt had an alkaline material in it. The baker was then able to modify his formulation by adding some monocalcium phosphate,” Zelch adds.

Facing down challenges

One of the biggest challenges of fermentation is maintaining control over the environment so the end product is consistent in flavor and texture. As a result, sourdough, which develops its flavor from the bacteria in the environment, will vary in flavor if not produced under controlled conditions.

All-natural sourdough or sponge and dough flavors can help bakers produce more consistent flavors from batch to batch. Sourdough flavor differs by the type of bacteria strain and can vary from the popular San Francisco sourdough to an Alaskan sourdough, which has more of a German rye-type flavor. “Our sponge and dough flavor can reduce fermentation times by up to 50 percent,” Dewilde says. “One of the great qualities is the functionality to reduce fermentation times because you're getting the performance out of the regular fermentation process, but you're adding a consistent flavor.”

Consistency is not only a factor in finished product flavor, but also in dough handling. If a sponge is a couple of degrees lower in temperature, it will be under-fermented and have a pH that's above the desired pH of 4.7 to 4.9. “That's going to give what we call younger dough characteristics, which means the grain tends to be more open and the yeast is going to move slower,” Zelch says. If the baker is monitoring temperature, he can mix the dough longer, which will improve extensibility and expansion. If the volume is still low, the baker can lower the oven temperature at the beginning of the bake, so the loaf's structure doesn't set too quickly.

“With older dough, if over-fermented, the baker will cut mixing time,” Zelch adds. “He may have to increase the oven temperature in the first zone to hold the expansion down because gassing is occurring too rapidly.”

The fermentation process is a complex system that requires adequate time for the OEM to design, depending on the baker's desired methodology, Harris notes. An efficient and effective solution can be accomplished when bakers provide OEMs with substantial input on factors related to its operations, including space availability and cost constraints. Both equipment and ingredient suppliers can help bakers produce a consistent, high quality product from batch to batch.