Fillings: Whats Inside Counts

By Donna Berry, Contributing Editor

Study after study shows that an increasing number of Americans are trying to make better-for-you food choices on a more frequent basis, but sometimes its all about indulgence. Its no wonder why mom-and-pop bakeries continue to open up in urban environments, in-store bakeries are actually starting to bake again and newer packaged baked goods appear to have a bit more pizzazz than their counterparts from the past century.

Desserts are all about indulgence, and consumers continue to be intrigued with multitextured baked goods, such as those encountered with so-called filled products like pies, macaroons and kolache," says Skip Julius, culinary solutions manager, Sensient Flavors, Indianapolis. Its almost as if the textural differences experienced with such products add a layer of indulgence, resulting in an oral sensation that is not possible with a simple sugar cookie or slice of pound cake."

Filling variations

Bakery fillings are as varied as the baked goods in which they have application, from coffee cakes to cookies to pies. They are typically based on fruit, cream, shortening or eggs, and vary considerably in manufacturing and distribution. Depending on the components, fillings can be aerated, emulsified or thickened. If aseptically processed or retorted, they can be distributed at ambient temperature. Other fillings require refrigerated or freezing temperatures.

Some bakers choose to make their own fillings; however, theres a booming market of industrial-produced fillings that not only provide convenience but also consistency. Regardless, when selecting a filling, careful consideration must be made regarding the fillings water content.

It is important that moisture migration between the baked goods crust and the filling be managed. This is most important in packaged retail products with a lengthy shelf life, such as toaster pastries and cereal bars. With frozen baked goods, freeze/thaw stability must also be factored in. Bakers want the moisture to be bound in the filling, as the more bound the water, the fewerand smallerthe ice crystals. Ice crystals have a negative impact on product quality, as they contribute to freezer burn and sogginess. Thus, fillings are often stabilized for specific applications, with proper stabilization necessary for a quality finished product.

Quality considerations

When selecting a stabilizer system for the manufacture of a bakery filling, product designers have to consider many variables to consider to ensure that the stabilizer does not adversely impact color or flavor release, two of the most important product features for consumers. The stabilizers influence on pumpability in a commercial setting must also be factored in.

For example, a filling will be pumped through a filler requires a viscosity that prevents splattering during machine filling into the crust or grain-based carrier. However, theres also a maximum viscosity to allow even pumping. Fillings must remain fluid enough to be pumped, but still build enough viscosity during baking to prevent boil out. This process requires a specially designed stabilizer system that imparts filling viscosity and allows for additional thickening during baking.  

Further, many bakery fillings are designed to be shelf stable, which also influences the stabilizer system. Common hurdles to ensure microbial stability of fillings are water activity, pH and processing temperature. Conditions to be met for a filling to be shelf stable are a pH below 4.6 and a water activity of 0.85 or less, combined with pasteurization or some form of heat processing," says Maureen Akins, food scientist, TIC Gums, White Marsh, MD. Most fillings will meet these criteria through the strategic use of stabilizers and the baking step. The pH requirement, however, is only met by the addition of acidulants to fruit fillings.

In general, when selecting a stabilizer for a filling, variables to consider include ingredient characteristics, such as pH, total solids, protein interactions, presence of minerals, etc.; processing conditions, such as heat treatment, hot filling, oven conditions, freezing conditions, etc.; and storage and shelf-life requirements," says Akins. These variables help determine the requirements of the stabilizer system." More often than not, the system is a blend of hydrocolloids, ranging from starches to gums to pectins.

Depending on the process and storage conditions, a variety of starchesmodified and nativecan be used in the production of fruit and cream-style fillings. All provide slightly different functionalities," says Leslie Drew, senior technologist, savory applications, Ingredion Inc., Westchester, IL. For example, modified tapioca starch provides a clean flavor and a low hot viscosity, which could be beneficial for processing, while native waxy maize starch has good process tolerance to acid and shear. Native waxy potato starch has a clean flavor and good clarity.

You want the starch ingredient to thicken the filling, while providing a short, smooth, creamy texture," Drew continues. The starch should enable the filling to achieve bake stability and prevent boil-out. With some fillings, the starch should provide a soft set and gel texture.

Some starches can reduce fruit solids in fruit fillings by providing a pulpy, grainy texture, which may lead to cost savings," says Drew. Some starches are used to provide freeze/thaw stability in the products, while some help with moisture management and enhancing shelf life. In addition, starches can be used to prevent moisture migration between crust or pastry and filling.

Starches with varying levels of acid tolerance are available, which is important, because if you select a starch with insufficient acid tolerance, it will produce a filling that is thin, runny and/or cohesive," Drew continues. When choosing a starch, in addition to the pH, you also need to look at your processing conditions (time, temperature and shear), as well as the sugar level in your formula. Sugar increases the gelatinization temperature of the starch, making it more difficult to cook out. In a high-sugar formula, if you use a starch that has sufficient acid tolerance you need to ensure that the starch is optimally cooked. We normally suggest that you cook the starch with a portion of the sugar and add the remaining sugar after cooking. For example, in a formula that is 50% sugar, cook the starch with two-thirds of the sugar. Once the starch is cooked, add the remaining one-third sugar. You could also use a cold-water swelling starch, also known as instant starch, which would eliminate the cooking step and allow the starch and all of the sugar to be added together."

Starches come in instant and cook-up forms. Instant starches do not require a heating process and can be used directly in the product," explains Drew. Bakers who create their own fillings will often rely on instant starches to simplify the production process."

Janae Kuc, senior research and development scientist, Gum Technology Corp., Tucson, AZ, adds that modified starch and tara gum work very well together to bind moisture in fruit fillings. The tara gum helps to provide a creamy texture and promotes viscosity. The two work together synergistically to build structure and texture, which is especially important in reduced-sugar or no-sugar-added fruit fillings.

This modified starch-tara gum stabilizer system also prevents moisture migration from the filling to the cake, crust or grain-based carrier," says Kuc. It can help keep fillings from becoming too molten during heating, preventing the filling from flowing out of or off the baked good.

Pectins are also very useful in fruit fillings, as they help promote gelation, are stable in low pH and provide a clear product," says Kuc. Depending on the application, they can help prevent boil-out, as well as suspend fruit pieces."

Akins concurs: More pH-tolerant hydrocolloids, such as pectin, work best in high-acid fruit environments. They provide a cuttable set and are resistant to syneresis. High-shortening systems can use guar gum to help stabilize air-containing fillings like those found in a creme horn."

When it comes to cream fillings, or those based on custard or pudding, "carrageenan will help promote a creamy texture and will aid in set and structure," says Kuc. In order to obtain a dense, rich, smooth consistency, locust bean gum or tara gum is often used in combination with carrageenan. These two gums help to create viscosity and reduce syneresis, while the carrageenan smooths out the filling and provides a fatty mouthfeel and texture.

Meringues need a stabilizing system that will promote aeration while maintaining structure," says Kuc. In general, methylcellulose and hydroxypropyl methylcellulose are a good choice for this type of filling."

Contemporizing filling flavors

Consumers dont actually recognize that a filling is stabilized. They will only be critical when quality is negatively impacted. But what they do notice immediately is flavor, as indulgence is all about the pleasure of taste.

And, as with most foods and beverages, todays consumers have come to expect much more from the taste of their desserts. Its no longer simply peach pie. Its roasted peach or caramelized peach or peach with rosemary," says Julius. Pies have become super trendy because they provide a recognizable base yet offer a canvas to decorate with innovative nuances.

Bakers are learning how to take a familiar flavor print and contemporize it," adds Julius. Consumers are comfortable with apple pie and, therefore, are willing to take a walk on the wild side when exploring pies filled with heirloom apple or really juicy green."

Tom Payne, industry specialist, U. S. Highbush Blueberry Council, San Mateo, CA, adds: Blueberry-based fillings are great in trendy flavor pairings that are unusual and inspiring, and can provide pies and other filled grain-based foods an unexpected, savory side. For example, blueberries pair surprisingly well with caramelized garlic, thyme, wasabi, salted pistachio and aji chili peppers. They sparkle with vivid, complementary flavors like maple, orange blossom honey, light molasses, balsamic and ginger."

But its not just fruit fillings that are contributing to the resurgence of pies. Bakers are reinventing custard- and cream-filled pies by adding an ethic twist," says Julius. Examples include crème brûlée, cannoli and Nutella® custard.

Americans are embracing Nutella, the Italian roasted hazelnut, skim milk and cocoa spread. This has led to a trend in other nut-butter-based fillings, in particular those based on almond and pistachio," says Julius. Applications extend beyond pies, and include all types of cookies and cakes.

And, when it comes to chocolate- and coffee-cream fillings, they now are plantation-specific or sport a fair-trade logo, as consumers are more aware of ingredient sourcing," Julius adds. Knowing that some cocoa or coffee farmers family will benefit from a dessert purchase contributes to that permission to indulge." 

Theres also a growing trend in layering the fillings in pies, such as dark and white chocolate creams with a layer of cherries. When different textures are involved, such as cream and fruit pieces, different oral sensations are triggered, which contributes to a more satisfying eating experience," says Julius. Depending upon the textures, some flavor release will be staggered, whiles other flavors linger."

The French macaroon presents a unique, dual-texture experience, and bakers continue to explore filling flavors that range from sweet to savory. And, just like with cupcakes, color has come to play an important role in French macaroons, with both the cookie and the filling," says Julius. But, to achieve bright, colorful hues using flavoring ingredients, the taste profile might be too powerful. For example, with a lemon basil filling, it makes sense to add yellow color to provide an illusion of flavor without causing the mouth to pucker from too much lemon extract.

Fruits healthful halo

An element unique to fruit pies, which is likely a contributing factor to their increasing popularity, is the actual fruit component. At a time when we are being told to consume more fruits and vegetables, fruit pies provide permission to indulge," says Julius. Consumers seem to be able to rationalize that a slice of fruit pie can be part of their daily fruit intake."

Almost any fruit can be used to make a filling, and depending upon the form and variety of fruit selected, the filling can contain whole pieces of the fruit or more closely resemble a jam, jelly or preserve. For example, fresh raspberries are very delicate, and when cooked to make a filling, lose product integrity. Other forms, such as individually quick frozen (IQF), dehydrated or infused, are more forgiving to the effects of heat, and will help the raspberry better retain its whole shape. Fresh apples, on the other hand, when sliced or diced, are quite durable and will retain their shape during the cooking process.

To make the actual filling, the fruit source is combined with sweetener, stabilizer and an acidulant. Traditional sweeteners such as sucrose, glucose and high-fructose corn syrup provide necessary solids, in addition to sweetness. The solids impact the texture and mouthfeel of the filling, in addition to affecting the specific gravity of the system. This impacts the distribution of the fruit throughout the filling and the baked-good application. The system should allow for even distribution of fruit pieces and particulates, and prevent them from sinking to the bottom or floating to the top.

Sweetener solids also help protect the fruits integrity by depressing the freezing point in frozen baked goods. Freezing-point depression reduces the chance of ice crystals developing, which prevents the fruit structure from being damaged.

Stabilizers also provide solids, contributing to mouthfeel and texture, as well as viscosity and particulate suspension. From an ease-of-use perspective, lower-viscosity fruit fillings are more prone to boil-out of bakery products when they are being baked. They can also result in excessive moisture movement to the grain-based portion of the baked good, producing an undesirable, soggy consistency. Depending upon the stabilizer, it can also contribute to heat stability and freeze/thaw stability, and prevent the filling from drying out and forming a surface crust. The processing and packaging of the filling dictates the choice of stabilizer.

Acidulants are added for both flavor modification and food safety, as lower-pH systems help protect against microbial growth. This is very important in shelf-stable applications. 

Acidulants are multi-functional ingredients that can impart sourness, improve taste, enhance flavor, control pH, provide buffering, chelate trace metals and improve antioxidant and preservative functionality. They are differentiated by form, flavor and solubility, and thus careful consideration must be made based on the desired impact.

For example, if the goal is to simply lower pH, as in the case of a raspberry filling, lactic acid is a wise choice, as its impact on flavor is almost negligible. However, if you want to add some citrus or sour undertones, then citric acid might be used. If tart is what you are going for, then choose adipic acid.

Malic acid is unique among acidulants used in fruit fillings, as it provides more buffering capacity when the pH is close to 3.2, which is the pH of most pectin-based gels. Using malic acid better stabilizes the pH of the pectin-set fruit filling, which in turn stabilizes texture and flavor. Malic acid also enhances fruit flavors by prolonging their release.

A little goes a long way, with usage levels in the range of 0.2% to 0.5%. Acidulants are typically added at the end of the fruit filling manufacture process to minimize any disruption of the system.

Typical canned fruit fillings that contain fruit pieces or particulates will range from about 70% (apple) to 75% (strawberry) moisture content, with a water activity of 0.92 to 0.94 and pH of 3.0 to 3.5. Blended fruit fillings, such as lemon curd, have a much lower moisture content, around 65%, while the increasingly popular no-sugar-added" style of fruit fillings will be higher in moisture, often in the range of 85% to 90%. The latter is due to the missing solids from the carbohydrate sweetener.

Indeed, missing solids are one of the challenges  in using high-intensity sweeteners as a sugar replacement in fruit fillings designed for baked goods. For starters, it is important to build the proper texture back into the system," says Michele Canar, manager, technical service and application development, PureCircle Ltd., Oak Brook, IL. It is also critical to control the water activity, in particular in extended shelf-life, shelf-stable products.

We have been successful using all-natural stevia to replace the sweetness of sugar, and when we include starch and maltodextrin, we can achieve a consistency that is similar to the sugar-sweetened fruit filling," says Canar. Glycerin has proven to be very helpful with binding water to maintain low water activity." 

Nutty fillings

Nut butters are growing in popularity and, much like fruit, depending upon the characterizing nut in the filling, may contribute a nutritional element to the baked good. For example, almonds are the tree nut highest in protein, fiber, calcium, vitamin E, riboflavin and niacin, and are recognized as being heart healthy," says John Csukor, CEO, KOR Food Innovation, Ashland, VA.

Jennifer Eastman, R&D scientist, Blue Diamond Almonds, Global Ingredients Division, Sacramento, CA, adds: Almond paste has long been used as a filling for pastries. Almond paste contains ground blanched almonds along with sugar, preservative and natural flavor." Almond paste adds visual appeal, as well as flavor and mouthfeel.

Bakers are learning that there are many opportunities to turn whole nuts into indulgent baked-good fillings. Almonds come in many forms and specifications and, once processed, in addition to yielding different particulate sizes, all varieties have their own personalities and flavor characteristics," says Csukor. Characteristic variations range from the creamy texture and vanilla flavor notes of blanched, skinless almonds to the definitive warm flavor tones and textures of roasted almonds.

It is also important to assess the textural needs of the filling for the baked good," continues Csukor. Smooth textures can be created using a creaming method of purèed, soaked/blanched raw almonds, while crushed, toasted or cooked almonds provide crackle and crunch."

Pecans and walnuts have also been used in a similar fashion, with more novel nutssuch as cashews, hazelnuts and pistachiosmaking their way into the filling scene. By design, in general, nutty fillings are low-water, high-solids and non-acidified systems, which makes stabilization less of an issue, as compared to high-moisture, fruit-based fillings. They are usually blended with sweetener, and sometimes butter or shortening. When high amounts of fat are included, it is often necessary to include an emulsifying gum, such as propylene glycol alginate, to prevent separation of oil during baking. If a hydrocolloid is required for thickening the nut filling, gums such as guar, locust bean and konjac typically provide a cleaner flavor release than starch.

Custard-style fillings can have a twist when nut milks or cremes are used as an alternative to dairy. Formulations can range from replacing heavy cream in a pastry cream or milk in a custard base," adds Kelly Sayko, director R&D, KOR Food Innovation. By using almond milk or almond creme, the intensity of a cooked note is much richer and deeper. Almond creme, butter, milk and flour can be used to increase and stabilize viscosity in coverture, meringue and custard-style filling formulas. The rich texture and stability of almond ingredients can aide in carrying flavor compounds and ensure a smooth, rich mouthfeel." Such bakery cremes must be carefully stabilized to prevent emulsion separation during cooking. 

As consumer desire for innovative flavors and unique textures in their foods continues to grow, bakers will want to revisit the category of fillings. As always, whats inside really does count.  

Donna Berry, president of Chicago-based Dairy & Food Communications, Inc., has been writing about product development and marketing for 13 years. She has a B.S. in food science from the University of Illinois in Urbana-Champaign. She can be reached at [email protected].