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Refrigerated Dough
Refrigerated Dough D Domingues and C Dowd, General Mills Inc., Minneapolis, MN, USA W Atwell, Bill Atwell Consulting, Champlin, MN, USA ã 2016 Elsevier Ltd. All rights reserved.
Topic Highlights
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Pressurized refrigerated dough product formulation, processing, and packaging Nonpressurized refrigerated dough product formulation, processing, and packaging Basic relationships governing refrigerated dough products Shelf life issues and solutions New developments in refrigerated dough technology
oxygen is beneficial. As with pressurized dough products, specific processes have been developed to deliver a wide array of nonpressurized, refrigerated, fresh dough products. These include ready-to-bake piecrusts and many different types of slice-and-bake cookies.
Pressurized Refrigerated Dough Formulation
Learning Objective
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To gain general understanding of refrigerated dough products, processes, and packaging
Introduction In the 1920s, an out-of-work baker named L.B. (Lively) Willoughby from Bowling Green, Kentucky, pursued the revolutionary concept of delivering fresh biscuit dough to consumers. In 1931, he obtained a patent describing the process and packaging designed to market refrigerated biscuit dough in a pressurized can. The biscuit dough had a shelf life of about 1 week. Lively initially marketed his product as Ye Old Kentucky Buttermilk Biscuits. He soon sold his business to the Ballard and Ballard Company who subsequently initiated the proliferation of refrigerated dough products. In 1951, Pillsbury acquired the Ballard and Ballard Company. The Pillsbury brand of refrigerated dough products now contains over 80 different products, and the technology has developed to deliver products with shelf lives in excess of 3 months. Perhaps even more than other food products, formulation, processing, and packaging are intimately related for pressurized refrigerated dough products. If leavened dough is mixed and refrigerated without packaging, the shelf life will only be a few hours. Carbon dioxide will diffuse out of the dough mass, and the resultant dough when baked will be very dense. Contact with oxygen can also cause changes in the dough that limit shelf life. Processes specific to pressurized refrigerated dough have been developed to deliver products from biscuits, to crescent rolls, to loaves. Clearly, Willoughby’s solution to package dough in a pressurized carbon dioxide atmosphere provided the means to provide fresh dough to consumers with an extended shelf life and founded the refrigerated dough business that exists today. Of course, not all baked products are leavened. For example, the dough used to make most cookie and piecrust doughs contains no leavening, and packaging under pressure is not required. Oxygen can still be very detrimental to this type of dough, however, and packaging providing a barrier to
Reference Module in Food Sciences
One commonality among pressurized refrigerated dough products is that they are all chemically leavened. Sodium bicarbonate is the carbon dioxide source in most products. Potassium bicarbonate can be used to formulate low sodium products. In proper combination with an acidulant, a specific amount of bicarbonate will reliably generate a specified amount of carbon dioxide and hence result in predictable can pressures in the final packaged products. Alternately, standard baker’s yeast is resourceful in identifying substrates to produce carbon dioxide in refrigerated dough formulas, and yeasted dough pressures will build quickly leading to burst cans in only hours. It is for this reason that the largest marketing category (e.g., biscuits) in refrigerated dough products is normally chemical leavened, whereas those that are normally yeasted (e.g., breads) are a smaller category in comparison. With respect to American-style biscuits, chemical leavening is not a limiting restriction. In general, biscuit formulas are similar to bread formulas with chemical leavening replacing yeast. Many nonpressurized biscuits are made with soft wheat flour, but pressurized refrigerated biscuit dough is made on high-speed lines, and hence, the cohesiveness of hard wheat dough is required. The category of refrigerated biscuits has been highly proliferated since the days of Lively Willoughby. In general, these proliferations have been effected through innovative means of incorporating shortening in the formula. Shortening can be mixed into the dough matrix, added as flakes, or sheeted into the dough to yield a laminated structure. Of course, there have been many size and flavor proliferations as well. Table 1 contains a typical refrigerated biscuit dough formula. The formulas for refrigerated sweet goods are similar to biscuits with the exception that they contain more sugar. The acidulant sodium acid pyrophosphate (SAPP) has a distinctive flavor that is very appropriate for biscuits but is sometimes deemed objectionable in sweet dough products. Hence, it is often replaced with sodium aluminum phosphate (SALP). Icings and fillings for canned sweet dough products can be included in plastic cups placed at the end of the refrigerated dough can. Many sweet dough product shape proliferations have been introduced based on different means of perforating and rolling the dough before packaging. Table 2 contains a typical sweet dough product formula.
http://dx.doi.org/10.1016/B978-0-08-100596-5.00246-8
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WHEAT PROCESSING | Refrigerated Dough
Table 1
Typical refrigerated biscuit dough formula
Ingredient
Weight (%)
Baker’s (%)
Hard wheat flour Water Shortening (dough) Shortening (roll-in) Sodium bicarbonate Sodium acid pyrophosphate (SAPP) Nonfat dry milk Dried whey Salt
51.8 30.8 2.0 8.0 1.0 1.4 2.0 2.0 1.0
100.0 59.5 3.9 15.4 2.0 2.6 3.9 3.9 1.8
Table 2
Typical refrigerated sweet dough formula
Ingredient
Weight (%)
Baker’s (%)
Hard wheat flour Water Shortening Sodium bicarbonate Sodium aluminum phosphate (SALP) Nonfat dry milk Sucrose Salt
50.2 29.8 10.0 1.0 1.0 2.0 5.0 1.0
100.0 59.4 19.9 2.0 2.0 4.0 10.0 2.0
According to the standards of identity, bread products must contain yeast. Refrigerated dough products similar to bread have been introduced, however. These products usually incorporate the very bland-tasting acidulant glucono delta-lactone (GDL) in combination with yeast flavors. The yeast flavors are complex and often are composed of a base flavor and a top note. Due to the fact that GDL is a fairly quick-acting acidulant, the sodium bicarbonate used in the chemical leavening system is often encapsulated to slow it down. This allows sufficient processing time to load the dough into the can and cap it. To obtain the high volume and the chewy texture associated with bread products, vital wheat gluten is usually added to the formula. Dextrose and/or nonfat dry milk is also included to facilitate Maillard browning. Panned-style breads have a distinctive shape that is not easily obtained directly from a can. For this reason, refrigerated dough ‘bread’ products are generally shaped like baguettes. Cans for the bread products are longer and have a lower diameter than those used for other pressurized refrigerated dough products. Table 3 contains the formula for a pressurized refrigerated dough product similar to bread.
Questions What leavening agents are commonly used in refrigerated dough products? Why can’t conventional baker’s yeast be used to leaven refrigerated dough?
Processing Table 3
Typical refrigerated bread dough formula
Ingredient
Weight (%)
Baker’s (%)
Hard wheat flour Vital wheat gluten Water Shortening Encapsulated sodium bicarbonate Glucono delta-lactone (GDL) Nonfat dry milk Sucrose Salt Bread base flavor Bread flavor top note
52.8 3.9 27.2 3.0 1.6 1.8 2.0 4.0 1.0 0.6 2.1
100.0 7.4 51.5 5.7 3.0 3.4 3.8 7.6 1.9 1.1 4.0
The processing steps to make refrigerated dough products are shown in Figure 1, and they are similar to many common bakery products. Basic engineering principles like mass balances and energy balances, along with physical and thermodynamic transformations, should be applied to each step, and specific details will depend upon the specific products being made. Good manufacturing practices, GMPs, and appropriate food safety systems like sifters and magnets are necessary considerations at every step, but those requirements will not be covered here.
Receive and store ingredients Bulk delivery of high-volume ingredients like flour and sugar via rail cars or trucks is common. Other ingredients are
Receive and Store Ingredients
Prepare and Scale/Meter Ingredients
Mix
Form
Finish
Pack into Primary Package
Pack into Secondary Package
Store and Distribute
Figure 1 Process steps for making refrigerated dough products.
WHEAT PROCESSING | Refrigerated Dough
handled in bags, boxes, super sacks, or liquid containers. Flour is typically stored in silos, so flour temperatures vary with the seasons, commonly ranging from 50 to 100 F (10–38 C). Many ingredients, however, have storage specifications for temperature, humidity, and age, which are provided by the ingredient vendors. Proper storage space near the point of use is desirable.
Prepare and scale/meter ingredients For operational efficiency, it is desirable to limit the number of individual ingredient streams entering the mixer. It is common, therefore, to create premixes or solutions of multiple ingredients. Major considerations include the reactivity of the blended components, ability to maintain a homogeneous blend, functionality during mixing, and cost. It is common to use pneumatic systems for transporting flour and other bulk powders from silos and storage vessels to scaling vessels. The most important step for making on-target dough is getting the right amounts of all ingredients into the mixer, so all ingredient delivery systems, whether automated or manual, must be properly engineered and verified. Vessels using load cells for either gain-in-weight or loss-in-weight scaling are typically accurate to within 1% of target, and mass flow meters for liquids can have similar accuracy. The most challenging ingredients to deliver accurately are the highly functional, smallquantity ingredients, like the leavening agents.
Mix The purpose of mixing is to transform the ingredients into dough with the desired bubble structure and physical properties. Important attributes of the dough include temperature, rheology, and density. Dough is a viscoelastic material, so its rheology includes measures of its viscous behavior as well as its elastic, or stretch, behavior. Horizontal bar batch mixers are common in the United States for high-speed dough processing operations due to their capacity and flexibility. The order of ingredient addition is important for refrigerated dough to ensure proper hydration of the flour and to limit the leavening reaction during mixing. Flour, water, and some minor ingredients are added first, with leavening agents and some other minor ingredients added later in the mixing cycle. The primary transformations in the mixer include uniform blending of ingredients, hydration, and gluten development. It is well known that gluten development is dependent upon mechanical energy, so mixing to an energy end point is an accurate way to control the degree of gluten development. Mixing is then defined by the amount of energy per unit mass of dough in the mixer, and mix energies for refrigerated dough are similar to other dough products, ranging from 25 to 55 kJ kg1. When all ingredient temperatures are accurately controlled, and heat exchanged to and from the mixer is constant, then mixing to a temperature end point is the same as mixing to energy. While high-speed mixing creates the gluten structure quickly, it also generates heat. High-capacity mixers are therefore jacketed with a coolant, typically propylene glycol and water solutions, to remove heat during mixing. Understanding the energy balance in dough mixing is essential to ensure low batch-to-batch variation in temperature and in degree of gluten development.
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Form After mixing, refrigerated dough should be formed and packed as quickly as possible. Unlike some yeast-leavened dough, there is never an advantage to resting or holding refrigerated dough. The chemical leavening reacts and there are changes within the gluten structure, and these changes have an impact on process tolerance and piece weight control. In general, dough should be packed within 30 min of mixing. Pairs of rolls, called gauging stations or roll stands, are used to transform a large mass of dough into a dough sheet of the desired width and thickness. The number of rolls needed, along with their speeds and gaps, depends upon the desired final sheet thickness. A common problem in dough processing is dough stickiness. Dusting agents like wheat flour or wheat starch are effective and economic. There are two basic approaches to creating the final dough pieces that go into the composite cans. Individual pieces are cut from the dough sheet and packed vertically into composite cans, or dough pads are cut, which include all individual pieces separated by perforations, and the pad is rolled up into a cylindrical shape to be packed into a can. Products for which we want a flaky texture have laminating fat extruded onto the middle third of the dough sheet early in the sheeting process, and the dough on either side of the laminating fat is folded over to enrobe the fat. The dough sheet then has a single layer of fat within a top layer and bottom layer of dough. After sheeting to the proper thickness, the fat-enrobed dough sheet is then folded back and forth on itself in a common process called lapping. Lapping creates multiple layers of dough and fat, and the number of fat layers is controlled by the amount of lapping.
Finish Finishing operations include the addition of toppings or fillings onto the dough sheet prior to packing. When a material is deposited onto a dough sheet, and then the individual pieces are cut and packed vertically, the material is a topping for each individual piece. When a material is deposited onto a dough sheet, which is cut into pads for rolling, then the material becomes a spiral filling. Finishing operations are highly specific to the product.
Questions Why is the order of ingredient addition important in making dough? How is it determined when mixing is complete? What is the shelf life for most refrigerated dough products?
Packaging The package used for pressurized refrigerated dough products is really quite ingenious. Dough is maintained in an expanded state in a carbon dioxide atmosphere, thus allowing it to be baked and achieve volumes similar to conventional baked products. The shelf life for these products has improved since the initial invention through improvements in can design, processing, and sanitation. Currently, the shelf life for pressurized refrigerated can dough products is about 3 months. The packaging system is composed of a composite spiralwound paperboard can with an aluminum liner and an iron
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WHEAT PROCESSING | Refrigerated Dough
Table 4
METAL END HEADSPACE O2 CO2 OXYGEN
OXYGEN
Typical refrigerated sugar cookie dough formula
Ingredient
Weight (%)
Baker’s (%)
Chlorinated soft wheat flour Sugar Shortening Water Salt Baking soda
46.8 24.5 18.7 9.0 0.4 0.6
100.0 52.4 40.0 19.2 0.8 1.3
Cookie Dough Processing
DOUGH COMPOSITE CAN BODY
The process for making refrigerated cookie dough follows Figure 1, but there is typically no separate finish step, and the details of the mix and form steps are different.
METAL END Figure 2 Refrigerated can dough system.
alloy can end. The spiral winding allows the pressurized can to easily open along the seam when struck on the side. The end is crimped on after loading the dough and the dough subsequently expands as the leavening system creates carbon dioxide. Air (oxygen) is vented and eventually, the dough caulks the vents in the can end and the system subsequently pressurizes. The can is designed to burst at about 40 psi as a safety control. Of course, higher pressures would lead to explosive opening and potential safety issues for consumers. Figure 2 diagrams the refrigerated can dough system. Can sizes vary with diameter and length to accommodate the various shapes and sizes of dough pieces and hence final product geometries. As described in the section ‘Processing,’ dough can be cut, rolled, and scored before loading into the can. The consumer, with very little manipulation, can bake these dough pieces to yield a large array of baked product forms.
Mix Cookie dough is considered an undeveloped dough because it is formulated with soft wheat flour, and there is no desire for a strong, developed gluten structure to hold gas during baking. Dough temperature and density remain important dough attributes, but cookie dough does not exhibit the same type of viscoelastic behavior as sweet rolls and breads. The primary transformations include blending to get a homogeneous dough and air incorporation for density control. To achieve these transformations, the mix element is typically a sigma blade, rather than horizontal bars. Continuous mixing is relatively straightforward, but careful consideration must be given to keeping any particulates, like chocolate chips, intact. Ingredient temperatures, the order of ingredient addition, and mix time are important parameters to achieve the desired dough attributes. Although cookie dough does not have a leavening reaction, it also changes with age, so for best process performance and weight control, cookie dough should be processed soon after mixing.
Form Question Explain the steps of can proofing and pressurization.
Nonpressurized Refrigerated Dough Cookies The primary ingredients in all cookies are sugar, flour, and shortening. This is the same for refrigerated cookie dough. Flour is generally derived from soft wheat, and it is chlorinated in the United States. For countries disallowing chlorination, other flour treatments (e.g., heat treatment) can be applied. Enough water is added to hold the mass together. The water activity of a refrigerated cookie dough is about 0.8 and hence microbial growth is minimized. Refrigerated cookie dough, like conventional cookie dough, is lightly leavened, so the final product is not too dense. Of course, there are many proliferations of cookie formulas. Table 4 contains the formula for a basic sugar cookie dough.
The most common general method of forming refrigerated cookie dough is extrusion, although there are many different ways to extrude the dough, and these result in different shapes and configurations. Extrusion includes pumping through a cylindrical mandrel to make a log or tube of cookie dough, using rolls to force dough through a rectangular die to create a slab, using rolls to force dough into cavities to make individual pieces, and using coextrusion, where different color dough streams are pumped through dies to create embedded shapes inside each cookie.
Cookie Dough Packaging There are two general types of packages for refrigerated cookie dough. The first is a film tube with metal clips on the ends. The second includes a paperboard carrier tray with a film overwrap. The shelf life of refrigerated cookie dough is about 4 months, and given the nature of the low-water formulation, cookie dough can be frozen to extend shelf life to several more months.
WHEAT PROCESSING | Refrigerated Dough
Piecrust
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Form
Piecrust dough consists of about 30% fat. Historically, many home economists considered the best piecrust dough to be made with lard. Modern piecrusts are more commonly formulated with shortening. The other components of conventional pie dough are chlorinated soft wheat flour, water, and salt. The formulation of refrigerated pie dough, however, is more complicated due to shelf life issues. Primary among these issues is the graying of the dough due to the action of polyphenol oxidase. Excluding oxygen by flushing the packaging with nitrogen helps reduce graying. Formulation approaches include replacing a major portion of the flour with wheat starch, gluten, and xanthan gum. This combination approximates the functionality of the flour in the formula but is void of the phenolic compounds and polyphenol oxidase that causes the gray color to develop. It also reduces the tendency for the dough to separate into a dough stage and a viscous syrup (i.e., syruping, described in the section ‘Shelf Life Issues’). Mold is another issue that can limit the shelf life of refrigerated piecrust dough. The use of antimycotics such as sorbate and propionate effectively increases the resistance of the dough to mold growth. Table 5 contains the formula for a typical refrigerated piecrust dough.
The most common general method of forming refrigerated pie dough is through sheeting rolls, die-cutting individual pieces, and then rolling the circular pieces for packaging.
Piecrust Packaging Refrigerated piecrusts are packaged in flexible film overwrap, each rolled crust in its own wrapper, and then two wrapped crusts are placed in a paperboard carton for the retail package. The shelf life of refrigerated pie dough is about 4 months, and given the nature of the low-water formulation, pie dough can be frozen to extend shelf life to several more months.
Questions What is the most common processing method employed to form refrigerated cookie dough? What formula changes are made to prevent refrigerated piecrust dough discoloration? What preservative is added to prevent mold growth in refrigerated piecrust?
Basic Relationships Magic Number
Piecrust Processing The general process for making refrigerated piecrust follows Figure 1, but there is typically no separate finish step, and the details of the mix and form steps are different.
Mix Pie dough is considered an undeveloped dough because it is formulated with soft wheat flour, and there is no desire for a strong, developed gluten structure to hold gas during baking. In fact, refrigerated piecrust dough has very little entrained gas. Dough temperature and density remain important dough attributes, and similar to cookie dough, piecrust dough does not exhibit viscoelastic behavior. The primary transformations include blending to get a homogeneous mix and restriction of bubble formation for density control. To achieve these transformations, refrigerated pie dough mixers typically have specialized mix elements along with pressure and vacuum control. Ingredient temperatures, the order of ingredient addition, and mix time are important parameters to achieve the desired dough temperature and density.
The notion of magic number is unique to canned refrigerated dough and was developed to describe a targeted dough pack weight to can volume ratio that reduces the likelihood of overor underpressurization and ensures optimal dough expansion upon opening. Magic number (MN) ¼ volume of can (cc)/weight of dough in can (g). Typical magic number ranges from 1.16 0.5 cc g1.
Pressure/Specific Volume Upon opening, pressurized refrigerated dough will expand rapidly and increase in specific volume (cc g1). There is a positive correlation between can pressure, dough specific volume after opening, and finished baked specific volume. This correlation is limited to pressures < 30 psig (pounds per square inch gauge). At can pressures exceeding 30 psig, the rate and extent of dough expansion upon opening result in damage to dough cell structure and loss in capacity to expand upon baking. Targeted equilibrated can pressures for most pressurized refrigerated dough products are between 14 and 20 psig.
Question Table 5
What is ‘magic number’ and why is it important to pressurized refrigerated dough?
Typical refrigerated piecrust dough formula
Ingredient
Weight (%)
Baker’s (%)
Chlorinated soft wheat flour Wheat starch Vital wheat gluten Water Shortening Salt Potassium sorbate
25.0 24.4 5.0 14.5 30.0 1.0 0.1
100.0 97.6 20.0 58.0 120.0 4.0 0.4
Shelf Life Issues Pressurized Dough Refrigerated dough products are active biological systems. Even at refrigerated temperatures, the enzymes introduced with the ingredients, primarily the flour, and the microbes introduced with the flour and from other sources can cause changes
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WHEAT PROCESSING | Refrigerated Dough
deleterious to dough quality. Primary shelf life problems associated with these changes are burst cans, syruping, gray dough, and crystal formation. The most significant shelf life issue for pressurized refrigerated dough products is burst cans. Lactic acid bacteria are the primary cause of this issue. As they produce lactic acid slowly during the product’s shelf life, the pH is depressed and the carbonate balance of the leavening system is driven to produce more gaseous carbon dioxide. Consequently, can pressures rise and eventually surpass the point where the cans will rupture and the contents will be expelled. The key to keeping lactic acid bacteria at a minimum in the dough is sanitation. Assuring old dough does not contaminate freshly processed dough is key. It is also important to control the temperature and time the products experience, especially during the can proofing step of the process. High temperatures and longer times foster the growth of the bacteria. Imperfections in the package such as can ends not fastened to specification can also be a significant factor. The cause of syruping is the enzymatic degradation of wheat flour arabinoxylans. Arabinoxylans are nonstarchy polysaccharides native to the flour, and they bind a very significant amount of water in freshly formulated dough. With time, these polymers are degraded, thus losing their water-binding ability. The result is a separation into a dough stage and a viscous syrup. The syrup facilitates the ionic flow between the aluminum liner of the can wall and the iron in the can end, and the package integrity is compromised. The result can be syrup exiting the can, resulting in a very serious product defect. Reduction in the incidence of syruping has been obtained by controlling the load of the enzymes responsible in the flour used. The possibility of enzyme inhibitors to control syruping has also been proposed. As discussed in the pie dough section, gray dough is caused by the polymerization of phenolic compounds native to flour. Excluding oxygen, which is one of the reactants, and/or reducing the amount of polyphenol oxidase in the system can minimize the reaction. The most common cause of gray dough is oxygen included in the can. This occurs of course if the can does not pressurize and hence the oxygen is not expelled. It can also occur if pockets of air are trapped against the sidewall. Polyphenol oxidase is contained primarily in the aleurone layer of the wheat kernel, which separates with the bran during milling. Therefore, using low-ash flour can also be beneficial. Crystal formation in refrigerated dough occurs only when leavening systems high in pyrophosphate content (i.e., SAPP) are used. Flour contains pyrophosphatase, which catalyzes the hydrolysis of pyrophosphate bonds, thus liberating two molecules of orthophosphate for every pyrophosphate molecule. This extremely high concentration of orthophosphate ions in the system creates a condition where visible sodium orthophosphate crystals can form in the system. When a product contains these crystals, consumers can mistake them for glass, and a very serious complaint occurs. Crystal formation has largely been eliminated in pressurized refrigerated dough products by using SAPP only in combination with SALP and other acidulants that are low in pyrophosphate content.
Nonpressurized Dough The enzyme-related shelf life issues with nonpressurized cookie dough products are minimized by the high sugar
contents and low-water activity of their formulations. Formulas for piecrust dough have also been developed to minimize enzymatic activity and related shelf life issues. Additionally, piecrust is packaged in a modified atmosphere to further reduce the risk of shelf life issues. One issue that does occur with piecrust involves a structural deficiency in the crust during baking. The term slumping has been used to describe the failure that occurs when the sidewalls of the crust slide to the bottom of the pie tin during a one-crust bake. The amount of fat in the formula is critical. Too much the crust will slump and not enough the texture will not be desirable. In general, refrigerated piecrust formulas contain less shortening than conventional piecrust dough to control slumping.
Questions Name the primary shelf life problems associated with refrigerated canned dough. How does lactic acid bacteria growth in refrigerated dough affect can pressure? What enzyme is responsible for gray dough discoloration? What are refrigerated dough crystals and what causes their formation?
New Developments Yeast Gaining the ability to use yeast in refrigerated dough products would likely expand the refrigerated dough market significantly. Most conventional baked products consumed are yeast-leavened, while all refrigerated dough products are chemically leavened. As described earlier, standard baking yeast is resourceful and able to consume and produce carbon dioxide with many of the substrates (i.e., monosaccharides) contained within freshly formulated and aging refrigerated dough formulas during shelf life. Significant effort has been expended to identify a yeast strain suitable for pressurized refrigerated dough. These include developing yeast strains that are temperature-sensitive and are not active at refrigerated temperatures, rehydrating yeast at reduced temperature to weaken it and render it unable to survive in the refrigerated dough environment, and using yeast strains limited in the ability to use all the substrates that commonly are available to standard yeast in the dough formula.
Nonpressurized Biscuit Dough Nonpressurized refrigerated biscuit dough and packaging technology were developed to enable portion control for consumers. Biscuits are packaged into individual film pouches (two biscuits per pouch) with four to five pouches per retail carton. This novel product and package format is a departure from traditional pressurized Willoughby dough systems and required redesigning how the product and package interact. Specifically, the use of nonpressurized pouches necessitated the development of an unleavened dough system. This was accomplished using encapsulated soda in combination with sodium aluminum phosphate, a heat-activated leavening acid. The pouches, made with high gas barrier film, are thermally formed to create a cavity to receive the biscuits and are
WHEAT PROCESSING | Refrigerated Dough
vacuum-packaged to limit headspace volume. Eliminating pouch headspace volume is critical to limiting the prereaction and release of leavening gas over shelf life time (minimizes pouch headspace expansion). Additionally, the enzyme glucose oxidase is added to the dough formula to prevent enzymatic discoloration resulting from oxygen diffusion into the package over shelf life time.
Low Sodium There is an ongoing desire to reduce the sodium content of refrigerated dough. The two main sources of sodium in refrigerated dough are added salt (NaCl) and chemical leavening agents (sodium bicarbonate and sodium-containing leavening acid salts). One commonly employed strategy to reduce sodium in refrigerated dough is to replace sodium salts with nonsodium analogs or organic acid substitutes (see Table 6). There are limits to this replacement strategy as potassium has a bitter astringent taste and some of the nonsodium leavening acid options do not possess comparable reaction rates to their sodium counterparts. Additionally, removing salt affects not only flavor but also dough water activity and gluten development. To complicate matters further, the molality of the dissolved salts in the dough system directly affects the dissociation of the leavening acid salts and leavening rate kinetics.
undeveloped cookie and brownie products. To expand glutenfree refrigerated dough to more developed product categories such as sweet rolls, crescent rolls, and breads, a need exists to create gluten-free dough with greater elasticity and tolerance to machinability.
Questions Name two of strategies to control yeast metabolism and gas production in refrigerated dough products. What are the two main sources of sodium in refrigerated dough? What technical hurdles must be addressed to expand glutenfree refrigerated dough product offerings to more developed product formats?
Exercises for Revision
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Gluten-Free Gluten (combination of gliadin and glutenin proteins) provides viscous and elastic properties to dough products. Functionally, these proteins enable entrapment of leavening gases, resulting in expansion to larger volume. Additionally, they provide a chewy texture to baked breads. Recent attention has focussed on a portion of the population that is sensitive to gluten and unable to eat products containing these proteins. The food industry has responded by developing many glutenfree bakery goods. Much of the ‘gluten-free’ technology developed to date relies on the use of nongluten flour systems (rice, sorghum, quinoa, legumes, etc.) in combination with starches (potato, corn, tapioca, etc.) plus hydrocolloids and gums (guar, xanthan, alginate, etc.). The resulting gluten-free batters and dough effectively entrap leavening gases enabling expansion upon baking but still lack elastic properties, thereby limiting product and processing options. This is particularly relevant to pressurized Willoughby refrigerated dough products, which are processed on high-speed lines and stored under pressure and need to retain gas cell structure upon rapid expansion when opened. As a result, many of the ready-to-bake glutenfree refrigerated dough offerings commercially available are Table 6
Sodium replacement salt analogs Sodium salt
Replacement salt
Salt Soda Leavening acida
NaCl NaHCO3 Na2H2P2O7 (SAPP)
KCl KHCO3 CaH2P2O7 (CAPP)
a
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Additionally, organic acids such as cream of tartar, malic, ascorbic, and citric can be used to replace inorganic sodium-containing acid salts.
What contribution did Lively Willoughby make that enabled the commercial development of refrigerated dough? How soon should (refrigerated) dough be packaged after mixing? Explain the two basic approaches to creating the final dough pieces that go into the composite cans. Hard wheat flour is used in essentially all canned refrigerated dough formulas. Why? Describe some of the possible product geometries achieved with canned refrigerated dough and how they are manufactured. What are two packaging formats for refrigerated cookie dough? Describe the relationship between can pressure, raw dough specific volume, and baked specific volume. What is the cause of syruping in refrigerated dough? Name a common strategy employed to reduce sodium in refrigerated dough.
Exercises for Readers to Explore the Topic Further
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Ingredient
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Shelf life extension and characterization: Refrigerated dough is unique in that the raw product is designed to be stored for up to 3 months with the expectation of acceptable baked performance through shelf life (color, volume, and taste). Research has linked protein content and flour enzyme activity (arabinoxylanase, polyphenol oxidase, and amylase) to changes in dough properties resulting in baked product quality decline over storage time. A more thorough identification and characterization of these intrinsic flour quality attributes are needed to more accurately predict and extend product shelf life. Gluten-free refrigerated dough: As mentioned earlier, glutenfree refrigerated dough products are presently limited to more underdeveloped applications (cookies, brownies, and piecrust), packaged in nonpressurized formats. There exists a need to create a more elastic gluten-free developed dough system with greater tolerance to processing and capability of being packaged in pressurized spiral-wound cans.
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WHEAT PROCESSING | Refrigerated Dough
Low-sodium refrigerated dough: In addition to the organoleptic challenges associated with reducing sodium, NaCl effectively lowers refrigerated dough water activity, which in turn limits lactic acid bacteria metabolic activity and associated changes in dough pH and can pressure. There exists a need to identify alternative ingredients and formulation strategies that will enable targeting of specific dough aw values while still meeting consumer organoleptic expectations. Whole wheat: The nutritional benefit of consuming wholewheat bread products is well documented. Inclusion of whole-wheat flour to refrigerated dough adversely affects shelf life and overall product performance due to increases in flour enzyme and bran levels. There exists a need to develop a whole-wheat flour system more compatible with refrigerated dough distribution and shelf life requirements (inactivation of enzyme systems and improvement in overall bake performance).
See also: Proteins: Enzyme Activities (00102); Wheat-Based Foods: Breads (00116); Wheat Processing: Milling and Baking, History (00158); Wheat, Dough Rheology (00161); Wheat, Grain Proteins and Flour Quality (00164).
Further Reading Atwell W (1996) Method to Reduce Syruping in Refrigerated Doughs. U.S. Patent 5,792,499. Atwell WA (2001) Wheat Flour. St. Paul, MN: American Association of Cereal Chemists. Domingues DJ, Atwell WA, and Pilacinski WP (1997) Yeast Leavened Refrigerated Dough Products. U.S. Patent 5,939,109. Gys W (2005) Substantiated Evidence for the Involvement of Arabinoxylans, Endoxylanases and Endoxylanase Inhibitors in Refrigerated Dough Syruping. PhD Thesis, Katholieke Universiteit Leuven, Belgium. Varriano-Marston E (1995) Packaging materials. In: Kulp K, Lorenz K, and Brummer J (eds.) Frozen and Refrigerated Doughs and Batters St. Paul, MN: American Association of Cereal Chemists. Willoughby LB (1931) Method and Means of Packeting Dough. U.S. Patent 1,811,772. Zoeller RJ and Henderson JR (1963) Dough Package. U.S. Patent 3,102,818.
Topic Highlights
• • • • •
Pressurized refrigerated dough product formulation, processing, and packaging Nonpressurized refrigerated dough product formulation, processing, and packaging Basic relationships governing refrigerated dough products Shelf life issues and solutions New developments in refrigerated dough technology
oxygen is beneficial. As with pressurized dough products, specific processes have been developed to deliver a wide array of nonpressurized, refrigerated, fresh dough products. These include ready-to-bake piecrusts and many different types of slice-and-bake cookies.
Pressurized Refrigerated Dough Formulation
Learning Objective
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To gain general understanding of refrigerated dough products, processes, and packaging
Introduction In the 1920s, an out-of-work baker named L.B. (Lively) Willoughby from Bowling Green, Kentucky, pursued the revolutionary concept of delivering fresh biscuit dough to consumers. In 1931, he obtained a patent describing the process and packaging designed to market refrigerated biscuit dough in a pressurized can. The biscuit dough had a shelf life of about 1 week. Lively initially marketed his product as Ye Old Kentucky Buttermilk Biscuits. He soon sold his business to the Ballard and Ballard Company who subsequently initiated the proliferation of refrigerated dough products. In 1951, Pillsbury acquired the Ballard and Ballard Company. The Pillsbury brand of refrigerated dough products now contains over 80 different products, and the technology has developed to deliver products with shelf lives in excess of 3 months. Perhaps even more than other food products, formulation, processing, and packaging are intimately related for pressurized refrigerated dough products. If leavened dough is mixed and refrigerated without packaging, the shelf life will only be a few hours. Carbon dioxide will diffuse out of the dough mass, and the resultant dough when baked will be very dense. Contact with oxygen can also cause changes in the dough that limit shelf life. Processes specific to pressurized refrigerated dough have been developed to deliver products from biscuits, to crescent rolls, to loaves. Clearly, Willoughby’s solution to package dough in a pressurized carbon dioxide atmosphere provided the means to provide fresh dough to consumers with an extended shelf life and founded the refrigerated dough business that exists today. Of course, not all baked products are leavened. For example, the dough used to make most cookie and piecrust doughs contains no leavening, and packaging under pressure is not required. Oxygen can still be very detrimental to this type of dough, however, and packaging providing a barrier to
Reference Module in Food Sciences
One commonality among pressurized refrigerated dough products is that they are all chemically leavened. Sodium bicarbonate is the carbon dioxide source in most products. Potassium bicarbonate can be used to formulate low sodium products. In proper combination with an acidulant, a specific amount of bicarbonate will reliably generate a specified amount of carbon dioxide and hence result in predictable can pressures in the final packaged products. Alternately, standard baker’s yeast is resourceful in identifying substrates to produce carbon dioxide in refrigerated dough formulas, and yeasted dough pressures will build quickly leading to burst cans in only hours. It is for this reason that the largest marketing category (e.g., biscuits) in refrigerated dough products is normally chemical leavened, whereas those that are normally yeasted (e.g., breads) are a smaller category in comparison. With respect to American-style biscuits, chemical leavening is not a limiting restriction. In general, biscuit formulas are similar to bread formulas with chemical leavening replacing yeast. Many nonpressurized biscuits are made with soft wheat flour, but pressurized refrigerated biscuit dough is made on high-speed lines, and hence, the cohesiveness of hard wheat dough is required. The category of refrigerated biscuits has been highly proliferated since the days of Lively Willoughby. In general, these proliferations have been effected through innovative means of incorporating shortening in the formula. Shortening can be mixed into the dough matrix, added as flakes, or sheeted into the dough to yield a laminated structure. Of course, there have been many size and flavor proliferations as well. Table 1 contains a typical refrigerated biscuit dough formula. The formulas for refrigerated sweet goods are similar to biscuits with the exception that they contain more sugar. The acidulant sodium acid pyrophosphate (SAPP) has a distinctive flavor that is very appropriate for biscuits but is sometimes deemed objectionable in sweet dough products. Hence, it is often replaced with sodium aluminum phosphate (SALP). Icings and fillings for canned sweet dough products can be included in plastic cups placed at the end of the refrigerated dough can. Many sweet dough product shape proliferations have been introduced based on different means of perforating and rolling the dough before packaging. Table 2 contains a typical sweet dough product formula.
http://dx.doi.org/10.1016/B978-0-08-100596-5.00246-8
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WHEAT PROCESSING | Refrigerated Dough
Table 1
Typical refrigerated biscuit dough formula
Ingredient
Weight (%)
Baker’s (%)
Hard wheat flour Water Shortening (dough) Shortening (roll-in) Sodium bicarbonate Sodium acid pyrophosphate (SAPP) Nonfat dry milk Dried whey Salt
51.8 30.8 2.0 8.0 1.0 1.4 2.0 2.0 1.0
100.0 59.5 3.9 15.4 2.0 2.6 3.9 3.9 1.8
Table 2
Typical refrigerated sweet dough formula
Ingredient
Weight (%)
Baker’s (%)
Hard wheat flour Water Shortening Sodium bicarbonate Sodium aluminum phosphate (SALP) Nonfat dry milk Sucrose Salt
50.2 29.8 10.0 1.0 1.0 2.0 5.0 1.0
100.0 59.4 19.9 2.0 2.0 4.0 10.0 2.0
According to the standards of identity, bread products must contain yeast. Refrigerated dough products similar to bread have been introduced, however. These products usually incorporate the very bland-tasting acidulant glucono delta-lactone (GDL) in combination with yeast flavors. The yeast flavors are complex and often are composed of a base flavor and a top note. Due to the fact that GDL is a fairly quick-acting acidulant, the sodium bicarbonate used in the chemical leavening system is often encapsulated to slow it down. This allows sufficient processing time to load the dough into the can and cap it. To obtain the high volume and the chewy texture associated with bread products, vital wheat gluten is usually added to the formula. Dextrose and/or nonfat dry milk is also included to facilitate Maillard browning. Panned-style breads have a distinctive shape that is not easily obtained directly from a can. For this reason, refrigerated dough ‘bread’ products are generally shaped like baguettes. Cans for the bread products are longer and have a lower diameter than those used for other pressurized refrigerated dough products. Table 3 contains the formula for a pressurized refrigerated dough product similar to bread.
Questions What leavening agents are commonly used in refrigerated dough products? Why can’t conventional baker’s yeast be used to leaven refrigerated dough?
Processing Table 3
Typical refrigerated bread dough formula
Ingredient
Weight (%)
Baker’s (%)
Hard wheat flour Vital wheat gluten Water Shortening Encapsulated sodium bicarbonate Glucono delta-lactone (GDL) Nonfat dry milk Sucrose Salt Bread base flavor Bread flavor top note
52.8 3.9 27.2 3.0 1.6 1.8 2.0 4.0 1.0 0.6 2.1
100.0 7.4 51.5 5.7 3.0 3.4 3.8 7.6 1.9 1.1 4.0
The processing steps to make refrigerated dough products are shown in Figure 1, and they are similar to many common bakery products. Basic engineering principles like mass balances and energy balances, along with physical and thermodynamic transformations, should be applied to each step, and specific details will depend upon the specific products being made. Good manufacturing practices, GMPs, and appropriate food safety systems like sifters and magnets are necessary considerations at every step, but those requirements will not be covered here.
Receive and store ingredients Bulk delivery of high-volume ingredients like flour and sugar via rail cars or trucks is common. Other ingredients are
Receive and Store Ingredients
Prepare and Scale/Meter Ingredients
Mix
Form
Finish
Pack into Primary Package
Pack into Secondary Package
Store and Distribute
Figure 1 Process steps for making refrigerated dough products.
WHEAT PROCESSING | Refrigerated Dough
handled in bags, boxes, super sacks, or liquid containers. Flour is typically stored in silos, so flour temperatures vary with the seasons, commonly ranging from 50 to 100 F (10–38 C). Many ingredients, however, have storage specifications for temperature, humidity, and age, which are provided by the ingredient vendors. Proper storage space near the point of use is desirable.
Prepare and scale/meter ingredients For operational efficiency, it is desirable to limit the number of individual ingredient streams entering the mixer. It is common, therefore, to create premixes or solutions of multiple ingredients. Major considerations include the reactivity of the blended components, ability to maintain a homogeneous blend, functionality during mixing, and cost. It is common to use pneumatic systems for transporting flour and other bulk powders from silos and storage vessels to scaling vessels. The most important step for making on-target dough is getting the right amounts of all ingredients into the mixer, so all ingredient delivery systems, whether automated or manual, must be properly engineered and verified. Vessels using load cells for either gain-in-weight or loss-in-weight scaling are typically accurate to within 1% of target, and mass flow meters for liquids can have similar accuracy. The most challenging ingredients to deliver accurately are the highly functional, smallquantity ingredients, like the leavening agents.
Mix The purpose of mixing is to transform the ingredients into dough with the desired bubble structure and physical properties. Important attributes of the dough include temperature, rheology, and density. Dough is a viscoelastic material, so its rheology includes measures of its viscous behavior as well as its elastic, or stretch, behavior. Horizontal bar batch mixers are common in the United States for high-speed dough processing operations due to their capacity and flexibility. The order of ingredient addition is important for refrigerated dough to ensure proper hydration of the flour and to limit the leavening reaction during mixing. Flour, water, and some minor ingredients are added first, with leavening agents and some other minor ingredients added later in the mixing cycle. The primary transformations in the mixer include uniform blending of ingredients, hydration, and gluten development. It is well known that gluten development is dependent upon mechanical energy, so mixing to an energy end point is an accurate way to control the degree of gluten development. Mixing is then defined by the amount of energy per unit mass of dough in the mixer, and mix energies for refrigerated dough are similar to other dough products, ranging from 25 to 55 kJ kg1. When all ingredient temperatures are accurately controlled, and heat exchanged to and from the mixer is constant, then mixing to a temperature end point is the same as mixing to energy. While high-speed mixing creates the gluten structure quickly, it also generates heat. High-capacity mixers are therefore jacketed with a coolant, typically propylene glycol and water solutions, to remove heat during mixing. Understanding the energy balance in dough mixing is essential to ensure low batch-to-batch variation in temperature and in degree of gluten development.
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Form After mixing, refrigerated dough should be formed and packed as quickly as possible. Unlike some yeast-leavened dough, there is never an advantage to resting or holding refrigerated dough. The chemical leavening reacts and there are changes within the gluten structure, and these changes have an impact on process tolerance and piece weight control. In general, dough should be packed within 30 min of mixing. Pairs of rolls, called gauging stations or roll stands, are used to transform a large mass of dough into a dough sheet of the desired width and thickness. The number of rolls needed, along with their speeds and gaps, depends upon the desired final sheet thickness. A common problem in dough processing is dough stickiness. Dusting agents like wheat flour or wheat starch are effective and economic. There are two basic approaches to creating the final dough pieces that go into the composite cans. Individual pieces are cut from the dough sheet and packed vertically into composite cans, or dough pads are cut, which include all individual pieces separated by perforations, and the pad is rolled up into a cylindrical shape to be packed into a can. Products for which we want a flaky texture have laminating fat extruded onto the middle third of the dough sheet early in the sheeting process, and the dough on either side of the laminating fat is folded over to enrobe the fat. The dough sheet then has a single layer of fat within a top layer and bottom layer of dough. After sheeting to the proper thickness, the fat-enrobed dough sheet is then folded back and forth on itself in a common process called lapping. Lapping creates multiple layers of dough and fat, and the number of fat layers is controlled by the amount of lapping.
Finish Finishing operations include the addition of toppings or fillings onto the dough sheet prior to packing. When a material is deposited onto a dough sheet, and then the individual pieces are cut and packed vertically, the material is a topping for each individual piece. When a material is deposited onto a dough sheet, which is cut into pads for rolling, then the material becomes a spiral filling. Finishing operations are highly specific to the product.
Questions Why is the order of ingredient addition important in making dough? How is it determined when mixing is complete? What is the shelf life for most refrigerated dough products?
Packaging The package used for pressurized refrigerated dough products is really quite ingenious. Dough is maintained in an expanded state in a carbon dioxide atmosphere, thus allowing it to be baked and achieve volumes similar to conventional baked products. The shelf life for these products has improved since the initial invention through improvements in can design, processing, and sanitation. Currently, the shelf life for pressurized refrigerated can dough products is about 3 months. The packaging system is composed of a composite spiralwound paperboard can with an aluminum liner and an iron
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WHEAT PROCESSING | Refrigerated Dough
Table 4
METAL END HEADSPACE O2 CO2 OXYGEN
OXYGEN
Typical refrigerated sugar cookie dough formula
Ingredient
Weight (%)
Baker’s (%)
Chlorinated soft wheat flour Sugar Shortening Water Salt Baking soda
46.8 24.5 18.7 9.0 0.4 0.6
100.0 52.4 40.0 19.2 0.8 1.3
Cookie Dough Processing
DOUGH COMPOSITE CAN BODY
The process for making refrigerated cookie dough follows Figure 1, but there is typically no separate finish step, and the details of the mix and form steps are different.
METAL END Figure 2 Refrigerated can dough system.
alloy can end. The spiral winding allows the pressurized can to easily open along the seam when struck on the side. The end is crimped on after loading the dough and the dough subsequently expands as the leavening system creates carbon dioxide. Air (oxygen) is vented and eventually, the dough caulks the vents in the can end and the system subsequently pressurizes. The can is designed to burst at about 40 psi as a safety control. Of course, higher pressures would lead to explosive opening and potential safety issues for consumers. Figure 2 diagrams the refrigerated can dough system. Can sizes vary with diameter and length to accommodate the various shapes and sizes of dough pieces and hence final product geometries. As described in the section ‘Processing,’ dough can be cut, rolled, and scored before loading into the can. The consumer, with very little manipulation, can bake these dough pieces to yield a large array of baked product forms.
Mix Cookie dough is considered an undeveloped dough because it is formulated with soft wheat flour, and there is no desire for a strong, developed gluten structure to hold gas during baking. Dough temperature and density remain important dough attributes, but cookie dough does not exhibit the same type of viscoelastic behavior as sweet rolls and breads. The primary transformations include blending to get a homogeneous dough and air incorporation for density control. To achieve these transformations, the mix element is typically a sigma blade, rather than horizontal bars. Continuous mixing is relatively straightforward, but careful consideration must be given to keeping any particulates, like chocolate chips, intact. Ingredient temperatures, the order of ingredient addition, and mix time are important parameters to achieve the desired dough attributes. Although cookie dough does not have a leavening reaction, it also changes with age, so for best process performance and weight control, cookie dough should be processed soon after mixing.
Form Question Explain the steps of can proofing and pressurization.
Nonpressurized Refrigerated Dough Cookies The primary ingredients in all cookies are sugar, flour, and shortening. This is the same for refrigerated cookie dough. Flour is generally derived from soft wheat, and it is chlorinated in the United States. For countries disallowing chlorination, other flour treatments (e.g., heat treatment) can be applied. Enough water is added to hold the mass together. The water activity of a refrigerated cookie dough is about 0.8 and hence microbial growth is minimized. Refrigerated cookie dough, like conventional cookie dough, is lightly leavened, so the final product is not too dense. Of course, there are many proliferations of cookie formulas. Table 4 contains the formula for a basic sugar cookie dough.
The most common general method of forming refrigerated cookie dough is extrusion, although there are many different ways to extrude the dough, and these result in different shapes and configurations. Extrusion includes pumping through a cylindrical mandrel to make a log or tube of cookie dough, using rolls to force dough through a rectangular die to create a slab, using rolls to force dough into cavities to make individual pieces, and using coextrusion, where different color dough streams are pumped through dies to create embedded shapes inside each cookie.
Cookie Dough Packaging There are two general types of packages for refrigerated cookie dough. The first is a film tube with metal clips on the ends. The second includes a paperboard carrier tray with a film overwrap. The shelf life of refrigerated cookie dough is about 4 months, and given the nature of the low-water formulation, cookie dough can be frozen to extend shelf life to several more months.
WHEAT PROCESSING | Refrigerated Dough
Piecrust
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Form
Piecrust dough consists of about 30% fat. Historically, many home economists considered the best piecrust dough to be made with lard. Modern piecrusts are more commonly formulated with shortening. The other components of conventional pie dough are chlorinated soft wheat flour, water, and salt. The formulation of refrigerated pie dough, however, is more complicated due to shelf life issues. Primary among these issues is the graying of the dough due to the action of polyphenol oxidase. Excluding oxygen by flushing the packaging with nitrogen helps reduce graying. Formulation approaches include replacing a major portion of the flour with wheat starch, gluten, and xanthan gum. This combination approximates the functionality of the flour in the formula but is void of the phenolic compounds and polyphenol oxidase that causes the gray color to develop. It also reduces the tendency for the dough to separate into a dough stage and a viscous syrup (i.e., syruping, described in the section ‘Shelf Life Issues’). Mold is another issue that can limit the shelf life of refrigerated piecrust dough. The use of antimycotics such as sorbate and propionate effectively increases the resistance of the dough to mold growth. Table 5 contains the formula for a typical refrigerated piecrust dough.
The most common general method of forming refrigerated pie dough is through sheeting rolls, die-cutting individual pieces, and then rolling the circular pieces for packaging.
Piecrust Packaging Refrigerated piecrusts are packaged in flexible film overwrap, each rolled crust in its own wrapper, and then two wrapped crusts are placed in a paperboard carton for the retail package. The shelf life of refrigerated pie dough is about 4 months, and given the nature of the low-water formulation, pie dough can be frozen to extend shelf life to several more months.
Questions What is the most common processing method employed to form refrigerated cookie dough? What formula changes are made to prevent refrigerated piecrust dough discoloration? What preservative is added to prevent mold growth in refrigerated piecrust?
Basic Relationships Magic Number
Piecrust Processing The general process for making refrigerated piecrust follows Figure 1, but there is typically no separate finish step, and the details of the mix and form steps are different.
Mix Pie dough is considered an undeveloped dough because it is formulated with soft wheat flour, and there is no desire for a strong, developed gluten structure to hold gas during baking. In fact, refrigerated piecrust dough has very little entrained gas. Dough temperature and density remain important dough attributes, and similar to cookie dough, piecrust dough does not exhibit viscoelastic behavior. The primary transformations include blending to get a homogeneous mix and restriction of bubble formation for density control. To achieve these transformations, refrigerated pie dough mixers typically have specialized mix elements along with pressure and vacuum control. Ingredient temperatures, the order of ingredient addition, and mix time are important parameters to achieve the desired dough temperature and density.
The notion of magic number is unique to canned refrigerated dough and was developed to describe a targeted dough pack weight to can volume ratio that reduces the likelihood of overor underpressurization and ensures optimal dough expansion upon opening. Magic number (MN) ¼ volume of can (cc)/weight of dough in can (g). Typical magic number ranges from 1.16 0.5 cc g1.
Pressure/Specific Volume Upon opening, pressurized refrigerated dough will expand rapidly and increase in specific volume (cc g1). There is a positive correlation between can pressure, dough specific volume after opening, and finished baked specific volume. This correlation is limited to pressures < 30 psig (pounds per square inch gauge). At can pressures exceeding 30 psig, the rate and extent of dough expansion upon opening result in damage to dough cell structure and loss in capacity to expand upon baking. Targeted equilibrated can pressures for most pressurized refrigerated dough products are between 14 and 20 psig.
Question Table 5
What is ‘magic number’ and why is it important to pressurized refrigerated dough?
Typical refrigerated piecrust dough formula
Ingredient
Weight (%)
Baker’s (%)
Chlorinated soft wheat flour Wheat starch Vital wheat gluten Water Shortening Salt Potassium sorbate
25.0 24.4 5.0 14.5 30.0 1.0 0.1
100.0 97.6 20.0 58.0 120.0 4.0 0.4
Shelf Life Issues Pressurized Dough Refrigerated dough products are active biological systems. Even at refrigerated temperatures, the enzymes introduced with the ingredients, primarily the flour, and the microbes introduced with the flour and from other sources can cause changes
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WHEAT PROCESSING | Refrigerated Dough
deleterious to dough quality. Primary shelf life problems associated with these changes are burst cans, syruping, gray dough, and crystal formation. The most significant shelf life issue for pressurized refrigerated dough products is burst cans. Lactic acid bacteria are the primary cause of this issue. As they produce lactic acid slowly during the product’s shelf life, the pH is depressed and the carbonate balance of the leavening system is driven to produce more gaseous carbon dioxide. Consequently, can pressures rise and eventually surpass the point where the cans will rupture and the contents will be expelled. The key to keeping lactic acid bacteria at a minimum in the dough is sanitation. Assuring old dough does not contaminate freshly processed dough is key. It is also important to control the temperature and time the products experience, especially during the can proofing step of the process. High temperatures and longer times foster the growth of the bacteria. Imperfections in the package such as can ends not fastened to specification can also be a significant factor. The cause of syruping is the enzymatic degradation of wheat flour arabinoxylans. Arabinoxylans are nonstarchy polysaccharides native to the flour, and they bind a very significant amount of water in freshly formulated dough. With time, these polymers are degraded, thus losing their water-binding ability. The result is a separation into a dough stage and a viscous syrup. The syrup facilitates the ionic flow between the aluminum liner of the can wall and the iron in the can end, and the package integrity is compromised. The result can be syrup exiting the can, resulting in a very serious product defect. Reduction in the incidence of syruping has been obtained by controlling the load of the enzymes responsible in the flour used. The possibility of enzyme inhibitors to control syruping has also been proposed. As discussed in the pie dough section, gray dough is caused by the polymerization of phenolic compounds native to flour. Excluding oxygen, which is one of the reactants, and/or reducing the amount of polyphenol oxidase in the system can minimize the reaction. The most common cause of gray dough is oxygen included in the can. This occurs of course if the can does not pressurize and hence the oxygen is not expelled. It can also occur if pockets of air are trapped against the sidewall. Polyphenol oxidase is contained primarily in the aleurone layer of the wheat kernel, which separates with the bran during milling. Therefore, using low-ash flour can also be beneficial. Crystal formation in refrigerated dough occurs only when leavening systems high in pyrophosphate content (i.e., SAPP) are used. Flour contains pyrophosphatase, which catalyzes the hydrolysis of pyrophosphate bonds, thus liberating two molecules of orthophosphate for every pyrophosphate molecule. This extremely high concentration of orthophosphate ions in the system creates a condition where visible sodium orthophosphate crystals can form in the system. When a product contains these crystals, consumers can mistake them for glass, and a very serious complaint occurs. Crystal formation has largely been eliminated in pressurized refrigerated dough products by using SAPP only in combination with SALP and other acidulants that are low in pyrophosphate content.
Nonpressurized Dough The enzyme-related shelf life issues with nonpressurized cookie dough products are minimized by the high sugar
contents and low-water activity of their formulations. Formulas for piecrust dough have also been developed to minimize enzymatic activity and related shelf life issues. Additionally, piecrust is packaged in a modified atmosphere to further reduce the risk of shelf life issues. One issue that does occur with piecrust involves a structural deficiency in the crust during baking. The term slumping has been used to describe the failure that occurs when the sidewalls of the crust slide to the bottom of the pie tin during a one-crust bake. The amount of fat in the formula is critical. Too much the crust will slump and not enough the texture will not be desirable. In general, refrigerated piecrust formulas contain less shortening than conventional piecrust dough to control slumping.
Questions Name the primary shelf life problems associated with refrigerated canned dough. How does lactic acid bacteria growth in refrigerated dough affect can pressure? What enzyme is responsible for gray dough discoloration? What are refrigerated dough crystals and what causes their formation?
New Developments Yeast Gaining the ability to use yeast in refrigerated dough products would likely expand the refrigerated dough market significantly. Most conventional baked products consumed are yeast-leavened, while all refrigerated dough products are chemically leavened. As described earlier, standard baking yeast is resourceful and able to consume and produce carbon dioxide with many of the substrates (i.e., monosaccharides) contained within freshly formulated and aging refrigerated dough formulas during shelf life. Significant effort has been expended to identify a yeast strain suitable for pressurized refrigerated dough. These include developing yeast strains that are temperature-sensitive and are not active at refrigerated temperatures, rehydrating yeast at reduced temperature to weaken it and render it unable to survive in the refrigerated dough environment, and using yeast strains limited in the ability to use all the substrates that commonly are available to standard yeast in the dough formula.
Nonpressurized Biscuit Dough Nonpressurized refrigerated biscuit dough and packaging technology were developed to enable portion control for consumers. Biscuits are packaged into individual film pouches (two biscuits per pouch) with four to five pouches per retail carton. This novel product and package format is a departure from traditional pressurized Willoughby dough systems and required redesigning how the product and package interact. Specifically, the use of nonpressurized pouches necessitated the development of an unleavened dough system. This was accomplished using encapsulated soda in combination with sodium aluminum phosphate, a heat-activated leavening acid. The pouches, made with high gas barrier film, are thermally formed to create a cavity to receive the biscuits and are
WHEAT PROCESSING | Refrigerated Dough
vacuum-packaged to limit headspace volume. Eliminating pouch headspace volume is critical to limiting the prereaction and release of leavening gas over shelf life time (minimizes pouch headspace expansion). Additionally, the enzyme glucose oxidase is added to the dough formula to prevent enzymatic discoloration resulting from oxygen diffusion into the package over shelf life time.
Low Sodium There is an ongoing desire to reduce the sodium content of refrigerated dough. The two main sources of sodium in refrigerated dough are added salt (NaCl) and chemical leavening agents (sodium bicarbonate and sodium-containing leavening acid salts). One commonly employed strategy to reduce sodium in refrigerated dough is to replace sodium salts with nonsodium analogs or organic acid substitutes (see Table 6). There are limits to this replacement strategy as potassium has a bitter astringent taste and some of the nonsodium leavening acid options do not possess comparable reaction rates to their sodium counterparts. Additionally, removing salt affects not only flavor but also dough water activity and gluten development. To complicate matters further, the molality of the dissolved salts in the dough system directly affects the dissociation of the leavening acid salts and leavening rate kinetics.
undeveloped cookie and brownie products. To expand glutenfree refrigerated dough to more developed product categories such as sweet rolls, crescent rolls, and breads, a need exists to create gluten-free dough with greater elasticity and tolerance to machinability.
Questions Name two of strategies to control yeast metabolism and gas production in refrigerated dough products. What are the two main sources of sodium in refrigerated dough? What technical hurdles must be addressed to expand glutenfree refrigerated dough product offerings to more developed product formats?
Exercises for Revision
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Gluten-Free Gluten (combination of gliadin and glutenin proteins) provides viscous and elastic properties to dough products. Functionally, these proteins enable entrapment of leavening gases, resulting in expansion to larger volume. Additionally, they provide a chewy texture to baked breads. Recent attention has focussed on a portion of the population that is sensitive to gluten and unable to eat products containing these proteins. The food industry has responded by developing many glutenfree bakery goods. Much of the ‘gluten-free’ technology developed to date relies on the use of nongluten flour systems (rice, sorghum, quinoa, legumes, etc.) in combination with starches (potato, corn, tapioca, etc.) plus hydrocolloids and gums (guar, xanthan, alginate, etc.). The resulting gluten-free batters and dough effectively entrap leavening gases enabling expansion upon baking but still lack elastic properties, thereby limiting product and processing options. This is particularly relevant to pressurized Willoughby refrigerated dough products, which are processed on high-speed lines and stored under pressure and need to retain gas cell structure upon rapid expansion when opened. As a result, many of the ready-to-bake glutenfree refrigerated dough offerings commercially available are Table 6
Sodium replacement salt analogs Sodium salt
Replacement salt
Salt Soda Leavening acida
NaCl NaHCO3 Na2H2P2O7 (SAPP)
KCl KHCO3 CaH2P2O7 (CAPP)
a
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Additionally, organic acids such as cream of tartar, malic, ascorbic, and citric can be used to replace inorganic sodium-containing acid salts.
What contribution did Lively Willoughby make that enabled the commercial development of refrigerated dough? How soon should (refrigerated) dough be packaged after mixing? Explain the two basic approaches to creating the final dough pieces that go into the composite cans. Hard wheat flour is used in essentially all canned refrigerated dough formulas. Why? Describe some of the possible product geometries achieved with canned refrigerated dough and how they are manufactured. What are two packaging formats for refrigerated cookie dough? Describe the relationship between can pressure, raw dough specific volume, and baked specific volume. What is the cause of syruping in refrigerated dough? Name a common strategy employed to reduce sodium in refrigerated dough.
Exercises for Readers to Explore the Topic Further
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Ingredient
7
Shelf life extension and characterization: Refrigerated dough is unique in that the raw product is designed to be stored for up to 3 months with the expectation of acceptable baked performance through shelf life (color, volume, and taste). Research has linked protein content and flour enzyme activity (arabinoxylanase, polyphenol oxidase, and amylase) to changes in dough properties resulting in baked product quality decline over storage time. A more thorough identification and characterization of these intrinsic flour quality attributes are needed to more accurately predict and extend product shelf life. Gluten-free refrigerated dough: As mentioned earlier, glutenfree refrigerated dough products are presently limited to more underdeveloped applications (cookies, brownies, and piecrust), packaged in nonpressurized formats. There exists a need to create a more elastic gluten-free developed dough system with greater tolerance to processing and capability of being packaged in pressurized spiral-wound cans.
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WHEAT PROCESSING | Refrigerated Dough
Low-sodium refrigerated dough: In addition to the organoleptic challenges associated with reducing sodium, NaCl effectively lowers refrigerated dough water activity, which in turn limits lactic acid bacteria metabolic activity and associated changes in dough pH and can pressure. There exists a need to identify alternative ingredients and formulation strategies that will enable targeting of specific dough aw values while still meeting consumer organoleptic expectations. Whole wheat: The nutritional benefit of consuming wholewheat bread products is well documented. Inclusion of whole-wheat flour to refrigerated dough adversely affects shelf life and overall product performance due to increases in flour enzyme and bran levels. There exists a need to develop a whole-wheat flour system more compatible with refrigerated dough distribution and shelf life requirements (inactivation of enzyme systems and improvement in overall bake performance).
See also: Proteins: Enzyme Activities (00102); Wheat-Based Foods: Breads (00116); Wheat Processing: Milling and Baking, History (00158); Wheat, Dough Rheology (00161); Wheat, Grain Proteins and Flour Quality (00164).
Further Reading Atwell W (1996) Method to Reduce Syruping in Refrigerated Doughs. U.S. Patent 5,792,499. Atwell WA (2001) Wheat Flour. St. Paul, MN: American Association of Cereal Chemists. Domingues DJ, Atwell WA, and Pilacinski WP (1997) Yeast Leavened Refrigerated Dough Products. U.S. Patent 5,939,109. Gys W (2005) Substantiated Evidence for the Involvement of Arabinoxylans, Endoxylanases and Endoxylanase Inhibitors in Refrigerated Dough Syruping. PhD Thesis, Katholieke Universiteit Leuven, Belgium. Varriano-Marston E (1995) Packaging materials. In: Kulp K, Lorenz K, and Brummer J (eds.) Frozen and Refrigerated Doughs and Batters St. Paul, MN: American Association of Cereal Chemists. Willoughby LB (1931) Method and Means of Packeting Dough. U.S. Patent 1,811,772. Zoeller RJ and Henderson JR (1963) Dough Package. U.S. Patent 3,102,818.