Formulation of Stuffed & Filled Food Products
Big convenience and flavor sometimes come in small packages.
Stuffed sweet and savory delights, such as pierogi, calzones, pocket pastries, and filled pastas present challenges to processors. The biggest hurdle: Keeping the insides sumptuous—and inside—while having the outsides maintain their texture and integrity, be it fluffy, flaky, or crunchy.
For the stability of baked and microwaveable appetizers, it’s important that the product be able to hold its shape and cook evenly and all the way through. One of the most important factors to address in stuffed products, such as Hot Pockets, is moisture migration from the filling to the pastry.
“It all starts with the filling and its components,” says Janine Mosley, a research and development manager for Giraffe Foods Inc. “Sometimes, gums and starches can be added to the filling as well as to the pastry dough. However, for simplicity, using stable ingredients and ingredient forms in the filling can allow the formulator to forego these extras.” As an example, Mosely suggests using low-moisture ingredients such as dehydrated vegetables instead of IQF vegetables.
“If a formula calls for tomatoes, it’s possible to use sun-dried tomatoes instead of diced tomatoes to keep the water activity as low as possible, especially in the filling portion of the appetizer,” she adds.
Chinese soup dumplings or steamed buns, called xiaolongbao, are trendy delicacies consisting of a thin wrapper filled with soup. The wrapper can be leavened or unleavened and is usually made from wheat flour. The filling is traditionally pork, and the delicate balance of functional ingredients is the trick to containing the hot soup within the fragile wrapper.
Traditionally, gelatin powder is added to a soup base and brought up to temperature. The soup is then cooled down, allowing the gelatin to set into a firm gel. Once this has set, the soup is cut into small cubes and mixed with a meat filling. This aspic can then be easily handled by the production team or equipment and dosed into each dumpling wrapper.
When the dumpling is steamed for the final consumer, the temperature inside the bun will reach gelatin’s melting point, typically around 100°F. The soup gelatin returns to a liquid state, creating an encased portion of soup perfect for immediate consumption.
As gelatin falls out of favor due to vegan diets and certain labeling restrictions, alternatives are being developed. Some potato starches have been modified in order to be quite firm once cooled but to allow for a nice melt once heat is applied. Either xanthan gum or locust bean gum alone will create viscosity but not gels. However, when they are combined, there is a synergistic reaction between the polysaccharide xanthan and the plant galactomannan of locust bean gum, causing the two gums to create a soft, thermo-reversible gel.
This rheological property can be exploited in food applications to create a desired set. Xanthan gum and konjac gum in combination also act to create a more elastic gel structure. Food scientists are investigating these and many other ingredients to determine new synergies that will allow developers to be more creative in the lab.
However, while adding low-moisture particulates and solids to the filling can help with stability, it also adds cost to the formula. Usually, more premium products are those that contain a high ratio of filling to pastry. Formulators can weigh those added costs against savings in waste and returns and strike a balance between the two types of formats, if necessary.
Mind the Gap
As Mosley points out, the filling of a stuffed item typically heats up and cooks faster than the pastry, especially if that filling has a high liquid level. The goal is to avoid having cracks or gaps form in the outer shell or crust that would allow hot filling to burst from the pastry while it cooks. (Or worse, after the consumer reheats it and has it in hand.) In a product with a high filling-to-pastry ratio, ingredients such as methylcellulose can be used.
Methylcellulose thickens as it heats up, which helps hold the filling inside of the pastry. This helps the product maintain its shape and consistency. For some products, it also is possible to score the pastry so that steam can vent. This technique further helps prevent bulging and bursting after cooking or reheating.
Other functional ingredients that filling developers keep in their arsenal include methylcellulose blends. They work differently from methylcellulose alone. There are blends that have reversible thermo-gelling properties and can lend important binding capabilities to stuffed applications.
Ingredients that are liquid when hot and gel when cold are excellent options for the manufacturing team. Gelling at high temperatures protects filings from boiling out during the cook step, increases moisture retention, prevents syneresis, and slows moisture migration from the filling to the pastry. Gelling also enhances freeze-thaw stability and bake stability.
Examples of such ingredients include carrageenan, gellan gum, and certain instant starches. Instant starch also can be easily dispersed in hot or cold fillings to fine-tune the viscosity of the filling immediately before adding it to the hopper to deposit.
Using agglomerated, cold-water swelling starch ensures that the starch will disperse well throughout the mixture, without clumping and causing “fish eyes.” Such starches are available in non-GMO and organic varieties and deliver high functionality without compromising clean-label requirements.
Because the filling usually takes less time to cook than the pastry, it is important to use ingredients that help with Maillard browning of the pastry. Manufacturers often use starch and sugar slurries to coat the pastry to help with browning. This helps make the pastry appear optimally cooked during re-therm.
Shape of Things
On smaller-scale production lines, doughs are made in advance and allowed to rest. If the dough is not allowed to rest, it can shrink and compromise the final shape of the product. However, in manufacturing where efficiency is key, dough relaxants and other conditioners are employed to produce the same effect in a fraction of the time.
Sodium metabisulfite is one commonly used conditioner. It allows for enhanced mixing, sheeting, stretching, rolling, and forming of a product. The amino acid cysteine was once a popular and effective dough conditioner; however, it is manufactured from hydrolyzed poultry feathers or pig hair. Because of this, many manufacturers have moved away from using it as an ingredient. There are other sources of cysteine, but they are much more expensive.
The fat component of a dough also is a major contributor to the structural capabilities. Functionality tests comparing shortenings and high-oleic, soy oil-based margarines in puff pastry applications have shown that the puff pastries using the soy margarines had better bake height and structure compared to controls using palm shortening and partially hydrogenated oils (PHO). The soy margarine pastries also performed as well as those made with dairy butter.
Similar tests with pie crusts made with high-oleic soy-oil shortening showed similar results. The high-oleic soy shortening worked as well or better than PHO, and worked better than either palm oil-based shortenings or lard across multiple dough evaluations, including firmness, flakiness, baking height, and temperature workability.
Stuffed and filled sweet items have long proven to be popular breakfast treats. The best example, of course, is Kellogg Co.’s Pop Tarts, the flat pie crusts sandwiching a fruit filling or other sweet filling. The crust of this classic toaster pastry is a simple short wheat flour crust, with small amounts of modified starches and xanthan gum used to maintain its integrity.
The biggest break-out filled dessert in recent years is Japanese mochi, a bite-sized ice cream treat wrapped in a small but thick packet of steamed rice dough. Its singular texture is a result of both the ingredients and the techniques: Whole, short-grained sweet japonica rice is pounded into a dough until the starch develops a gel-like matrix.
Japonica rice is extremely low in amylose starch, while being high in amylopectin and protein, giving it its unique structure. After forming, the sticky dough is dusted with sweet rice flour or arrowroot powder to coat the outer surface and prevent sticking.
Within the trend for wrapping, filling, and stuffing various doughs, shells, and crusts, one classic item is enjoying an impressive renaissance: stuffed pastas. Ravioli, conchiglie, tortellini, and other filled farinaceous foods inspire thoughts of comfort and home cooking.
Whether fresh or frozen, the evolution of stuffed pasta varieties is nowhere more evident than in grocery, with the trickle-down effect of fine dining flavor combinations making consistent appearances in the home meal replacement sector.
“In the fresh-filled pasta category, we still see sales skewed toward the basics,” says Derek Vella, product developer for Loblaw Companies Ltd., a Canadian supermarket chain. “Consumers are still largely drawn to the classic fillings, including cheese, meats, mushrooms, and spinach.”
Vella describes how the North American understanding of where fresh pasta fits on the menu is still developing compared to Europe. “Historically, in our market, these products have been used as a quick crowd pleaser or an easy vegetarian entrée. The notion that it is strictly a value menu item is changing as more complex offerings are introduced.”
According to Vella, these product tiers are designed to appeal to consumers who have increasingly high expectations of what filled pasta can be. “We are always developing fillings in line with current trends but are mindful of finding a happy medium between the opportunity to introduce our customers to new flavors — such as ‘nduja [spicy Calabrian pork paste] and roast cauliflower — with more familiar flavors like chicken, spinach, and premium cheeses.”
Vella emphasizes how creating an offering that is functionally sound as well as flavorful involves more than just the right combination of sauce and pasta — it has to “strike the right balance between the amount of filling and the dough.” Loblaw’s stuffed pastas are presented as fresh, frozen, and in-home meal replacement hot tables. “The variability of holding temperatures and moisture conditions makes for a unique set of development challenges,” he says.
Hand to Hand
Batch production of hand-made stuffed pastas confronts similar challenges as does crafting them on a production line. One such challenge is controlling water activity in the filling to ensure stability and to preserve the structure and texture of the finished product. “If the moisture is too high,” explains Vella, “it will weaken the dough. As a general rule, we combat this by keeping the water activity (Aw) equal for the filling and the dough for fresh product.”
Filling amounts can range from 25% of the product weight to more than 60% in premium items. “The flavor delivery is worlds apart between a more dry filling at 25% compared to a richer, more fluid filling at 60%. They really are completely different product experiences,” Vella adds.
With the production of stuffed pasta, ensuring GMP is absolutely essential, not only for functional reasons but for food safety. To avoid the proliferation of dangerous pathogens, controlling factors such as Aw and pH is imperative. Chemical preservatives such as sodium benzoate can be incorporated into the pasta to prevent microbial growth.
Products that come pre-dressed require a sauce that is tolerant to re-therming. A functional blend of thickeners, including starches and gums, is key to developing a robust sauce that retains viscosity and, depending on the final preparation, can be key in mitigating purge in the fillings while maintaining desired viscosity.
Some modified or native corn starches can help bind the product and maintain stability through the freeze-thaw cycle. An example of such a development consideration would be maintaining the consistency of a creamy emulsified sauce or dairy sauce.
Rice flour is an alternative stabilizer that lends a silken texture to the filling with the added benefit of being a recognizable ingredient on the label that consumers are not scared of.
To ensure stability and desired consistency while holding at temperature or re-heating at home, phosphates or a blend of phosphates and modified starches are primary functional ingredients that can prevent syneresis and destabilization.
Developers tend to favor more homogenous fillings, as they are more simply introduced into the dough, and there are no issues with maintaining uniformity on the machinery. Fillings can be categorized as either dry or wet.
Adam Disapio, corporate “Red Seal Chef” for National Pasta Corp. retail stores, notes how the choice to go with a wet versus dry filling often depends largely on flavor — but the functionality of the line and the machinery should play into the decision as well. “Dry equipment stuffs using a combination of gravity and pressure, while wet filling is more advanced, using pneumatic filling,” he points out.
“The equipment manufacturers use to fill should be right for the composition of the filling mix,” cautions Disapio. “Dry filling should be about the consistency of a crumbling ball, easily malleable with the fingers. Depending on the ingredients, it’s important to control the moisture. But this could involve something as simple as squeezing ricotta to eliminate as much whey as possible and until it reaches specifications.”
Commenting on the technical aspect of developing products designed for filling, such as stuffed pastas, Vella notes, “At the opening price point, filled pasta manufacturers typically incorporate a lot of bread crumbs to ensure the moisture is low enough to work on a high-speed line.” He discusses how manufacturers have the option of creating a “value add” through substituting or incorporating ingredients that make an all-around improvement in the product, such as functional starches in the filling.
For example, a dry polenta starch in an Italian filling is perceived less as a filler, contributes flavor, enhances marketability, and still maintains a clean label. Various quality proteins, fats, and oils, or select cheeses and meats, can be used to lower water activity. “However, if the filling has a high proportion of oil, there is an additional risk of it bleeding into or even through the outer layer,” Vella cautions.
With the Grain
There has been a growing proliferation of value-added pasta products that include whole grains, ancient grains, and alternative starches. However, these present difficulties due to the inability of these ingredients to form a highly aggregated, compact gluten network as refined pasta does.
The most stable fillings are those that contain processed cheese and ham or bacon because these components are inherently stable. They usually contain emulsifiers and phosphates (which assist with moisture retention) and are high in fat and low in moisture. On the other hand, seafood fillings are more challenging because of their high moisture content.
A whole wheat pasta only forms a loosely aggregated protein network that is less able to hold the starch granules in place. As a consequence, the pasta has a lower integrity, softer texture, and a less firm bite.
Though the protein matrix might not be as stable, drying processes (such as low-temperature/low-time versus high-temperature drying) can help keep the gluten in place and improve the bite of the pasta. The less refined whole-wheat pasta inherently possesses a higher fiber content, which is likely to become a marketing powerhouse in regard to health benefits. If adding a gluten-free halo to the product, the flour can be replaced by functional gums, such as xanthan or guar.
Newly popular pulse proteins such as fava bean, can also be incorporated as a functional and cost-effective alternative to egg whites in certain pasta doughs. Developers may choose to use resistant starch in order to replace some flour and reduce the carbohydrate count on the nutritional label.
With products destined for re-therming, there is the additional hurdle of moisture migration and dough strength. The choice of flour used will be a deciding factor in the quality of the end product. The ratio of amylose to amylopectin, as well as the chain length of the starches, will determine the water binding capacity and final moisture content of the dough. Semolina flour has proven to be a predictable choice, time-honored over many centuries.
“For most pasta manufacturers, there is not a lot of divergence from traditional ingredients, the classic combination of semolina flour, eggs, water, and salt,” says Vella. Some manufacturers use natural color — often vegetable powders — to add visual interest and contribute to the overall shelf appeal.”
The quality of pasta is largely dependent on the hardness of the flour used and, for egg pastas, the amount of egg in the dough. More egg results in a more premium dough, as it contributes to the protein needed for strength and elasticity, with the ability to be rolled thinly and still prevent breakage.
Premium pasta dough can be as thin as 0.6mm, whereas you can get value offerings in excess of 1 mm in thickness. While that might seem like only fractions of a millimeter, it’s a difference that consumers can detect, and it makes an enormous difference in the eating quality.
“Controlling moisture of the filling and considering the final shapes of your pasta are the most important considerations when addressing manufacturing challenges,” says Vella. “Complex or delicate shapes with sharper points are the most susceptible to breakage in handling, packaging, and storage, especially in frozen products which become very brittle.”
Another consideration that Vella raises is the preparation instructions for consumers. “Breakage of the pasta through overcooking is the source of the majority of complaints,” he says. “Adequately communicating handling and preparation on the packaging calls for explicit and detailed messaging.”
John Shackelford, Liz Chan, and Kirsten Benneter are research chef/food scientists in New Product Innovation for Giraffe Food & Beverage Inc. in Mississauga, Ontario. They can be reached through Mr. Shackelford at email@example.com.
Originally appeared in the March, 2019 issue of Prepared Foods as Get Stuffed!