Enzymes work behind the scenes
July 1, 2012
by Donna Berry
From economics to functionality, the natural biological catalysts known as enzymes are the secret to success for many commercial bakers. They accelerate reactions that naturally occur during the manufacture of baked foods, resulting in improved product quality and extended shelf life. Enzymes also help bakers advance production through better dough handling, tighter process control, effective flour correction and replacement of emulsifiers.
“Enzymes are attractive ingredients for bakers because they are extremely effective at their specific function and can be used at a fraction of the dosage of other ingredients, keeping shipping costs down and inventory space at a minimum,” said Nicole Rees, R&D manager, AB Mauri, Wilsonville, OR.
They are also label-friendly, according to Bernie Bruinsma, PhD, director of special projects, Caravan Ingredients, Lenexa, KS. “Enzymes can often eliminate the need for some chemical-sounding ingredients and, in doing so, provide a cleaner label and typically even an improved product,” he observed.
Consumers also have a positive view of enzymes as natural ingredients, said Troy Boutte, PhD, group manager, bakery, fats and oils, DuPont Nutrition and Health, New Century, KS. “Enzymes do not fluctuate in price nearly as much as similarly functioning ingredients, which appeals to manufacturers of price-sensitive baked foods such as sandwich bread.”
Enzymes are relatively expensive on a pound-for-pound basis, but a little bit goes a long way. “If one pound of an ingredient could be replaced with 100 parts per million of an enzyme, it could cost less,” Dr. Bruinsma said. He noted that enzymes earned their current high profile by keeping bread fresh for twice as long as bakers expected from the softeners they previously used. “Fewer loaves are returned to the bakery, and that more than pays for the initial cost of the enzyme,” he said. “It is best to factor in all of the benefits the enzymes provide before being scared away by the initial cost.”
So, just what are these highly specific and consistently effective functional ingredients? They are proteins.
“Enzymes are produced by plants, animals and microorganisms and are responsible for various life processes, yet they are not living organisms themselves,” said Jan van Eijk, PhD, research director, baking ingredients, Lallemand, Montreal, QC. They occur naturally in many bakery ingredients. But often, bakers find it most beneficial to supplement a batter or dough’s native enzymes content to maximize their functionality in a specific application.
“Each enzyme functions best at its own pH and temperature range, and the progress of the chemical reaction depends on these conditions along with time and concentration,” Dr. van Eijk added. “Most commercial enzymes are produced from microorganisms and are standardized for specific activities.”
Enzymes come from many sources. “The enzymes sold commercially are painstakingly selected from libraries of organisms collected from anywhere on earth,” Dr. Boutte said. Criteria include the enzyme’s ability to work well under baking conditions. They should also be easy to produce in high quantities and have few, if any, side activities. “It is also desirable to produce enzymes that are unaffected by naturally occurring enzyme inhibitors or by common bakery ingredients,” he said, citing certain enzymes that do not work well in the presence of sugar and shortening.
These proteins enjoy special status from a labeling standpoint. “Since enzymes modify dough properties during processing but are rendered inactive by the oven’s heat, they are present in the baked food only at insignificant levels,” said Michael Beavan, project manager, Watson Inc., West Haven, CT. “Therefore, enzymes fit the definition of a processing aid and are exempt from being identified on finished product ingredient legends.” However, many bakers do list them, because consumers percieve enzymes positively.
In a bakers’ basket
Six basic categories of enzymes are available to bakers: amylase, asparaginase, lipase, oxidase, protease and xylanase (also called hemicellulose and pentosanase). “There are enzymes that break down macromolecules such as protein and starch, and there are those that build up these same macromolecules,” Mr. Beavan said. “The first type is responsible for the extensible properties of dough, which allow it to flow, while the second type is responsible for the elasticity or strength of the dough.”
Alpha-amylases were the first enzymes used in the baking industry. Naturally occurring in malt as well as industrially produced through microbial fermentations, alpha-amylases are added to wheat flour to standardize natural amylase activity.
“Addition assures a certain minimal production of sugar for fermentation during baking,” Dr. Boutte said. Alpha-amylase degrades the starch in wheat flour into small dextrins, which allows yeast to work throughout dough fermentation, proofing and the early stage of baking. Bread volume and crumb texture thus improve. Also, the small sugars released by alpha-amylase enhance the Maillard reaction responsible for desirable browning.
“Remember, enzymes are very specific, so not all amylases are the same and may perform slightly differently,” Dr. Bruinsma said. “For example, if some of the by-products of an enzyme action are glucose or maltose, the bread may be sweeter or have a slightly darker crust.”
A special type of amylase — maltogenic amylase — modifies starch during baking, providing an anti-staling effect. Staling results from changes in the starch structure during shelf life and is associated with a loss of freshness. This happens because over time starch granules lose moisture and revert from a soluble to an insoluble form.
Previously, bakers used emulsifiers to slow this transformation. Today, they have learned that maltogenic amylase can modify starch during baking, making the granules more flexible during storage and retarding staling in many applications.
Wheat flour contains around 3% nonstarch polysaccharides — large polymers that absorb moisture and interact with gluten, the predominant protein in wheat flour. Although present only in small quantities, these carbohydrates account for about 25% of water absorption in wheat doughs and increase dough viscosity, which negatively affects loaf volume.
Commercialized in the past decade, the enzymes known as hemicellulase, pentosanase and xylanase cleave the chain structure of nonstarch polysaccharides, decreasing their water-holding capacity. This can improve dough machinability and result in a more stable dough.
Lipid, gluten modifiers
Standard wheat flour contains 1.0 to 1.5% lipids in a variety of forms. Some are able to stabilize the air bubbles in the gluten matrix; others are not. “The addition of lipase improves the stabilizing function of lipids, allowing them to function as natural dough conditioners,” Dr. van Eijk said. “The addition of lipase also results in the production of more uniform and smaller crumb cells, with crumb texture being silkier and color appearing to be whiter. Industrial chemical emulsifiers can also typically be eliminated from the formulation, which is very appealing in today’s clean-label formulating environment.”
Historically, chemical oxidants such as bromates, azodicarbonamide and ascorbic acid have been widely used to strengthen gluten, particularly in bread. Working with today’s enzymes, bakers discovered that oxidases can replace the use of such chemical oxidants.
When used under optimum conditions, enzymes can provide volume in the oven that bakers desire and the close crumb grain that consumers expect, according to Dr. Bruinsma. “With changes like this, some hope that even mediocre flour could be turned into good flour, but that has not yet been proven true,” he observed.
Dr. Boutte explained the mechanism that allows oxidase enzymes to replace chemical oxidants. “These enzymes oxidize sugars, thus producing resulting in the production of small amounts of hydrogen peroxide in the dough,” he said. Hydrogen peroxide acts directly on gluten as an oxidant, and when used with ascorbic acid, the enzyme-released hydrogen peroxide speeds up the action of the acid, itself a strong gluten cross-linking agent.
“The result of using oxidase enzymes is dough with much greater resistance to mechanical stress, ultimately resulting in greater volume and a finer crumb structure,” Dr. Boutte said. “These enzymes work particularly well in applications like grain breads and frozen dough where gluten development can be difficult.”
Proteases, on the other hand, break down gluten. “Proteases relax the dough for easier machining,” he continued, noting their use in cracker manufacturing. “Proteases can provide additional volume to baked foods, and exoproteases, in particular, can increase browning in baked foods by releasing amino acids that take part in browning reactions. This can lead to some additional flavor development.”
Recent interest in asparaginase stems from concerns about the formation of acrylamide, a potential carcinogen. “This substance is formed at high temperatures when the amino acid asparagine reacts with a reducing sugar like glucose,” Dr. van Eijk said. “To retard the formation of acrylamide in baked foods, the enzyme asparaginase was developed. It converts asparagine to aspartic acid, which does not take part in the formation of acrylamide.”
1 + 1 = 4
Many suppliers are exploring the synergies that exist between different enzymes. “It is not so much new enzymes but rather new combinations,” Mr. Beavan observed. “We offer a new enzyme system that combines specific oxidative and hydrolytic activities for production of expanded whole grain breads.”
Such synergistic effects add to in-use benefits. “Synergies exist between numerous enzymes, and we use this to the baker’s advantage when designing an enzyme system for a specific application,” Ms. Rees said. “It isn’t one plus one equals two; sometimes, it’s one plus one equals four.
“Enzymes can also have different side activities,” she added. “We’ve catalogued the behavior of hundreds of enzymes in each category.”
And behavior is at the heart of enzyme use in the bakery. “Regardless of the enzyme type, each can provide a separate benefit to baking if added in the proper amount and standard conditions are followed,” Dr. Bruinsma concluded. “If enzymes are used improperly, such as overuse or allowing them to work for too long a time, they can cause too much change and may be detrimental to the finished product.”