Progress in extended shelf life (ESL) in the bread category has been dramatic during the past two decades because of enzyme technology developed by Novozymes, Franklinton, N.C. Novamyl^®, a maltogenic amylase enzyme, not only provided a fresh-keeping solution for bread, but redefined the fresh bread industry. This technology has reportedly saved bakeries $4 billion in stale return costs since its inception.

When the benefits of ESL are factored in all along the value chain-from producer to consumer-the results are astounding. Included among these benefits are improvements in the bread's eating quality and consumer perception of the brand's value; fewer stale returns, resulting in a higher quantity of saleable bread for the baker's customers; longer distribution routes over an expanded geographic market area; and lower distribution and production costs.

ESL solutions not only involve textural issues, such as softness and resiliency, but mold prevention as well. While enzyme technology provides a solution for maintaining textural integrity over an extended period of time, other formulation and processing parameters are critical too. Finished product quality will deteriorate if these factors are not considered.

Delaying staling

Ultimately, the texture of bread should be soft, but resilient. If bread is soft and not resilient, it will not spring back in the mouth, which is an indication of gumminess. “Resilience equals crumb elasticity,” says Jan Van Eijk, Ph.D., research director, Lallemand Baking Solutions, Montreal. “Softness is how much force it takes to suppress the crumb. If the force pushes back some, that's resilience.”

Fresh keeping delays the effects of staling. “A major effect of staling is the increase in crumb firmness and the loss of fresh crumb springiness or elasticity over time,” says Todd Forman, staff scientist, Novozymes. “These changes in texture are due to changes in configuration of the flour's highly branched amylopectin starch molecules, either due to retrogradation/recrystallization, or perhaps to an increase in the number of complexes formed with the gluten protein in flour.”

Certain ingredients, such as enzymes and emulsifiers, interact with the starch molecule, and in so doing, control the change in its configuration. Amylase enzymes modify the size and structure of the starch molecule, Forman notes. Mono and diglycerides, an emulsifier and crumb softener, complexes with the amylose fraction of the starch molecule during baking, Van Eijk adds. While both methods often are used, the enzymatic approach is more effective on its own. As enzymatic activity differs from one type to another, it is important to choose wisely. Fungal amylases are generally heat labile and will thus become inactive before the starch in dough is available, which occurs above gelatinization temperatures greater than 140°F. While fungal amylase is effectively used as a flour supplement or dough improver, it's not particularly effective as a shelf -life extender.

Bacterial amylases were the first enzymes used to extend shelf life. Unlike the fungal amylases, bacterial amylases are thermostable and can therefore withstand heat. “Depending on the internal temperature of the baked product, upwards of 10 percent of the initial dosage of bacterial amylase could remain active when the bread leaves the oven,” Forman explains. “This means as the bread cools, the enzyme is still working slowly and could be reinvigorated when the bread is reheated during toasting.”

“This extended activity is particularly problematic due to the way the enzyme modifies the amylopectin molecule. It is rather aggressive, working deep within the molecule creating large branched dextrins. The amylopectin molecules become so broken down that the strength of the amylopectin structure is reduced and the inherent, fresh crumb springiness is destroyed. The resultant bread will be quite soft, but even a slight overdose could cause a very soft crumb to become sticky and gummy in texture,” Forman adds.

About 17 years ago, Novozymes patented a maltogenic amylase that forms the basis for most enzymatic shelf-life extenders used today. Instead of breaking down amylopectin as bacterial amylase does, this maltogenic amylase leaves amylopectin primarily intact, and instead generates small sugar molecules from the ends of the starch molecules. As a result, starch granules stay softer and more resilient longer, plus starch retrogradation is reduced, Forman notes.

Still, for the enzyme to be most effective, bakers may have to change the baking profile of their ovens to ensure the enzyme is most active during the baking process, as the starch can only be modified after it gelatinizes, Forman adds. Apart from the quality improvements derived from enzyme use, the labeling of enzymes is at the discretion of the baker, as enzymes are considered processing aids. Even if labeled, enzymes are reasonably well received by consumers and provide a clean label, notes Bernie Bruinsma, Ph.D., vice president, technology, Innovative Cereal Systems, Wilsonville, Ore.

Managing freshness

Even if the rate of staling is not decreased, certain ingredients can help bread stay softer for a longer period of time, notes Troy Boutte, Ph.D., director, Innovation Center, Caravan Ingredients, Lenexa, Kan. For instance, hydrated monoglycerides or powdered distilled monoglycerides will increase initial softness, but do not change the rate of staling. Some strengthening emulsifiers, such as sodium stearoyl lactylate (SSL) and ethoxylated monoglycerides, provide additional softness.

Dough conditioners that produce higher volume loaves also can enhance bread freshness. A loaf with a higher volume is more diluted with air, which enhances its softness, Van Eijk notes. Although these ingredients will not affect the rate of staling, the bread will be softer to begin with.