Formulations have been researched extensively to ensure products save operators time and the need for on-site expertise. For example, frozen dough is formulated with cryo-resistant yeast, and yeast flavors replace long fermentation processes.
Flour protein levels are adjusted to optimize dough mix time and gas retention during frozen storage. Although these adjustments contribute to labor savings, measures must also assure the end product delivers the desired eating experience. The consumer ultimately decides if he will purchase the baked good again.
In this article, baked goods are defined as baked dough products purchased at a bakery, such as rolls, buns, sweet rolls and breads. Cakes, cookies and other special occasion desserts are not included. Also, although water-binding ingredients such as gums, starches and fiber, as well as solutes, help improve freshness, this article focuses on emulsifiers and enzymes.
Defining FreshnessThe definition of baked good freshness differs depending on the product and customer. For example, artisan breads provide a crusty, crunchy exterior combined with a springy, resilient crumb. Some cinnamon rolls are loved for their moist, gummy, gooey consistency, and other rolls are desired for their bread-like texture. It is important to know finished product specifications, since this impacts which ingredients and anti-staling tools are chosen.
It also is important to know how products are handled and when they will be consumed. Rolls and breads purchased Friday evening may be consumed with a Saturday meal; cinnamon rolls purchased in the morning are brought to work. Upscale bakery products provided through a grocery delivery service are eaten after hours or days of ambient shelf life. Point of consumption data should be collected and communicated with the developers formulating the products. This information includes length of shelf life prior to consumption and re-thermalization steps such as the percent warmed in microwaves versus traditional ovens. Suppliers may be able to provide this market research data.
Key differences exist between wholesale fresh bread and frozen dough formulations. Large, wholesale bread manufacturers provide products sold in the fresh bread aisle of grocery stores. Since two-week shelflives must be obtained to be competitive, they are current on anti-staling and freshness preservation technology.
The use of freshness preservation technology for foodservice and in-store bakeries varies more. While some retailers purchase from manufacturers that use freshness preservation technologies, others do not. “Typically, dough formulas sold to foodservice and in-store bakeries tend to be very 'clean.' They do not contain the higher levels of sugar, fat, anti-staling enzymes and emulsifiers found in wholesale bakery formulations,” says Doug Edmonson, former vice president of Sara Lee Bakery Group (St. Louis), Ingredient Technology and Innovation. This may be intentional in that a single dough formula can then be used in a variety of products. Or perhaps the use of these tools is just not “top of mind.” The preconception exists that the items sold in these venues are consumed freshly baked.
Edmonson suggests there may be an opportunity to use the anti-staling/freshness technology from the fresh bread aisle and apply it to frozen doughs and par-baked breads in the in-store bakery and foodservice areas. The downside is the added cost in an already highly competitive business. However, Edmonson points out that research, by Robert Cooper, Ph.D., indicates that the number-one reason new products are successful is because they are high-quality, unique and differentiated.
“For institutional and foodservice products to take market share from the fresh baked aisle, they need to take advantage of the innovations in the fresh aisle. Consumers will pay more for these unique features of quality, freshness and shelf stability if they are plainly apparent to them,” says Edmonson.
Here is a closer look at some of the ingredient preservation tools that can help products meet this objective.
Tendering EmulsifiersAlthough starch retrogradation does not explain 100% of the staling in bread products, it is the most studied mechanism and probably contributes most to reduced quality. This staling mechanism can be modified. Starch retrogradation occurs when gelatinized starch molecules recrystallize and network to form ordered structures. Over time, this results in crumb firmness and a lack of resiliency.
When hydrophobic mono- and diglyceride emulsifiers are included in dough formulas, starch molecules do not swell or gelatinize as much during baking. Less gelatinized starch means fewer molecules will recrystalize and network. Mono- and diglycerides also form complexes with gelatinized amylopectin and interfere with this starch molecule's ability to recrystallize. Emulsifiers also form complexes with solubilized amylose and limit its ability to form an intergranular starch network.
Mono- and diglycerides with long saturated fatty acids are effective at softening the crumb throughout the bake cycle to the point of consumption. However, they soften in a way that reduces the springiness or resiliency of the crumb and tend to soften the bread crust as well. For this reason, they are not an ideal shelf life extension tool for crusty artisan-style breads.
Emulsifiers with higher HLB ratios such as ethoxylated mono- and diglycerides, polysorbates, sodium stearoyl lactylate (SSL) and diacetyl tartrate ester of monoglyceride (DATEM) help build a strong gluten network. SSL is unique in that it is an effective crumb softener (it complexes with the starch) and also is a dough strengthener.
Unlike other emulsifiers, DATEM does not complex with the starch and is used mainly as a dough strengthener.
DATEM can soften a bread product, but the resulting increased softness usually is due to the increased protein strength. Stronger protein films tend to increase volume, change air cell size and structure, and so on. DATEM is used often in crusty breads where a springy/resilient crumb is desired. Although the exact mechanism of these dough strengtheners is not known, the emulsifiers appear to interact with the hydrophobic regions of the gluten protein surfaces. They enhance the unfolding of the gluten proteins and, thus, enhance the networking/cross-linking of the gluten, forming a strong gluten network. This strong gluten network stabilizes the formation of thin protein films developed during mixing and baking, aids in the incorporation of air (nucleation) and helps prevent air bubble coalescence.
High HLB emulsifiers also control ice crystal development and movement, and preserve air cell structure during freezing and frozen storage. As ice crystals grow, hydrated proteins lose water. When they melt, the proteins do not rehydrate. The dough becomes wet, sticky and difficult to use.
Enabling EnzymesLike mono- and diglycerides, amylase enzymes moderate bread staling by preventing starch recrystallization. However, they do so by a different mechanism. Three steps must occur to ensure softness preservation with amylases:
- In the presence of water, starch molecules start to swell (gelatinize) at about 60ÞC. This forms an open, amorphous state that allows enzymatic cleaving. (Enzymes are not able to act on intact, non-swollen starch granules.)
- After this gelatinization step, the amylase then must “break up” the starch molecule and modify the way it recrystallizes post-bake. Enyzmes are most active within a specific temperature range.
- The enzyme must be inactivated by heat during baking.
Anti-staling enzymes (bacterial amylases), commercialized 30 years ago, were difficult to control. They made non-specific cleaves in the swollen starch granule, resulting in loss of starch structure and, thus, loss in bread product structure. Also, early enzymes were thermally stable; 25% of enzymatic activity remained after baking. The enzymes would continue to soften or “digest” the starch molecules as the bread product cooled and perhaps even longer. A gummy texture resulted, especially if the enzymes were overdosed.
Enzyme technology has evolved and improved over the last 12 years. Bacterial amylases are engineered to cleave the starch molecules at one or two specific sites, leaving the basic backbone structure intact. Further enzymatic action then is limited to the non-reducing ends of the amylopectin molecule. The starch, thus, can provide crumb structure in the finished bread product. These new amylases also are functionally inactivated during baking (at approximately 90ÞC). “There can be drawbacks to these new enzyme cocktails if overused. I have observed a lot of crushed fresh bread in the market place,” said Edmonson. “Any ingredient solution used to excess can create other problems in the operations and distribution system of a bakery. The last thing a consumer would ever do is buy a flattened package of buns on the bottom of the fresh or in-store shelf.”
By inhibiting starch recrystallization while maintaining the structural contribution of starch, the new enzymes are useful in a range of products. For example, in artisan breads, the springiness/chewiness of the crumb is an important characterizing feature along with the thick, crunchy crust. Amylases help preserve crumb chewiness and maintain this texture during shelf life. This is difficult to do with emulsifiers, which provide shelf life softness, but also tend to alter the texture of the bread's interior and soften the crust. “Emulsifiers will only go so far,” says R. Carl Hoseney, Ph.D., R&R Research Services (Manhattan, Kan.). “Enzymes are needed for superior softness and long shelf life.”
Pentosanases and LipasesPentosans (polymers of 5-carbon sugars) comprise 2% to 3% of white flour. Their molecular weight determines their degree of solubility. While they hold many times their weight in water, which is beneficial to the baker, the insoluble pentosans tend to interfere with the gluten-forming protein's ability to form optimum networks. Pentosanases modify these components, allowing the gluten proteins to unfold efficiently and network, forming strong protein films.
White flour contains some 1.0% to 1.5% of lipid material. About 40% of the lipids are polar; the rest are non-polar. Non-polar lipids bind with hydrophobic regions of the gluten proteins and limit protein networking and strength. Lipases modify these associations with the proteins and allow gluten to become more functional. New lipases act on specific polar lipids so that they become more polar. These modified lipids stabilize films surrounding gas bubbles that are formed during proofing and baking. Since pentosanases and lipases do not act on the starch, they do not extend directly the shelf life of bread products. However, they improve overall texture and softness by providing bread products with greater volume and finer, “silkier” crumb grain.
In summary, to formulate a baked good properly, marketing input is required. Questions to be answered include knowing how consumers eat a product (ambient, warmed, microwaved) and when (hours or days after baking). This consumption data should be incorporated as a variable during product development. Then, really understand the food mechanisms that must be controlled. How, at a molecular level, is the aged or abused product different than the “fresh” product? Coupling this information results in formulae that are robust to “real world” conditions.
Website Resourceswww.nps.ars.usda.gov/publications/publications.htm?SEQ_NO_115=123872 — Waxy wheat flour blends and bread staling
www.oardc.ohio-state.edu/swql/TEXT/publications.htm — Site to download Soft Wheat Quality research abstracts from the USDA - ARS from 1960
www.PreparedFoods.com/archives/2000/2000_10/ 0010denz.htm —Enzymes in staling prevention
www.bsb.org.uk/members/library/conferences/ 2000spring/paper_437.htm — Paper on Bread Quality from the British Society of Baking
www.aaccnet.org — American Association of Cereal Chemists