Food Product Design: Applications - February 2004 - Sweet Success: Nutty Confections

February 2004

Sweet Success: Nutty Confections

By Peter DeaContributing Editor

Nuts have long been a favorite ingredient of confectioners, adding flavor, texture, and visual interest to sweet creations. They pair well with most confections, especially chocolate ones, and can be incorporated in many forms: roasted or natural, whole, pieces or a paste. Adding nuts not only enhances eating qualities of the product, but also increases its perceived intrinsic value.  

Nuts open a new realm of creative possibilities. However, a few technical challenges arise for the confectionery technologist. This article will address potential problems in common nut-based confections and confectionery processes.

A changing image Not too long ago, when low fat was in vogue, many considered nuts as unhealthy because of their relatively high fat content. More recent information, however, advises that nuts can be part of a balanced nutrition plan. Most of the fats and oils found in common nuts are the healthy monounsaturated and polyunsaturated types. Also, nuts provide an important source of dietary fiber, phytosterols and other micronutrients, such as vitamin E, folate, magnesium and potassium. (For more information, see "Cooking Up Some Nutty Ideas" in the August 2003 issue of Food Product Design.) Incorporating nuts into confectionery products makes for a very enjoyable way of consumption.

The most common nuts used in the confectionery industry include peanuts, walnuts, cashews, hazelnuts, almonds, pecans, pistachios, Brazil nuts and macadamia nuts. Among these, a vast range of flavors and textures is available to the confectioner, as well as added nutrition and value. Other seeds that may fall into the nut category in terms of confectionery applications include sesame seeds, sunflower seeds and pine nuts.

Development considerations All nuts common to confectionery products are naturally high in fat, with cashews and pistachios ranking the lowest at 46%, and macadamias ranking the highest at 76%. The fatty-acid profiles of confectionery nuts tend to be high in oleic acid, a monounsaturated fatty acid, and linoleic and linolenic acids, which are polyunsaturated fatty acids. As a result, the fats of most nuts tend to be liquid at typical ambient conditions.  

For comparison, the major fatty acids in chocolate liquor (the primary source of fat in chocolate) are the saturated fatty acids palmitic and stearic acids, and the monounsaturated fatty acid, oleic acid. These tend to be solid at ambient conditions. The fat in chocolate is very different from those found in common confectionery nuts and, as a result, they are not very compatible. Nuts' high level of unsaturated fats, which are primarily liquid oil at ambient conditions, leads to the two major problems typically associated with chocolate-nut confections: oil migration and oxidative rancidity.

Despite the fact that their oils don't get along, chocolate and nuts seem especially well suited to each other in confectionery products. Simply using a whole nut as a decoration on a chocolate piece significantly enhances appetite appeal and adds a classic touch of elegance. Using chopped nuts as a coating or as an inclusion in confections adds texture and flavor. As fillings, nuts ground into butters and pastes provide richness and balance to overly sweet formulations. Roasted nuts add yet another appealing angle in both flavor and aroma, whether they are whole, chopped or ground.

Coating considerations The simplest chocolate and nut product is a chocolate-covered nut. Putting a layer of chocolate on a nut does not seem like an especially difficult task, but confectioners must weigh some considerations before starting.

Panning is a common method of coating nuts in chocolate or compound coating. In this process, the manufacturer places the centers (in this case, the nuts) in a revolving vertical pan, which typically is tilted at an angle of about 35? to allow proper tumbling of the pieces. As it revolves, the centers roll around in the pan, and the coating material is applied to the centers. The coating material spreads over the centers and eventually hardens; additional layers form on the product until the desired thickness and finish are achieved. Chocolate panning requires a source of cold (55? to 60?F) dry air at less than 60% humidity. Airflow depends on the size of the batch and the size of the pan.

When selecting a nut (or any center) for panning, obviously the roundest types, such as hazelnuts, peanuts, almonds (the smaller, short varieties, such as Mission, are almost oval and work well for panning) and macadamias, work best. A round piece will roll much easier and coat much more evenly, resulting in a product with a smooth, attractive appearance.

Also consider the quantity and type of chocolate for coating. Economics, of course, will factor into how much chocolate the manufacturer applies on the nuts. Take care not to build too thick of a layer on nuts with delicate, distinct flavors, such as hazelnuts, pistachios and almonds. Too much chocolate coating or a very strong chocolate (one with high cocoa solids) may overwhelm the natural nut flavors. However, enough chocolate must be applied to serve the functional purpose of coating the center -- a thicker layer of chocolate can minimize effects of oil migration. Also, although the coarse texture of nuts may mask the grittiness of a poorly refined chocolate, a well-refined chocolate may help slow the effects of some oil migration.

The naturally high fat content of nuts makes migration of their oils into surrounding materials a primary issue in creating a stable chocolate-nut confection. This phenomenon can cause bloom and soften the chocolate layer. As such, presealing the nuts first with a protective glaze layer helps to slow the oil migration into the subsequent chocolate coating. If the product has a thick layer of chocolate, this presealing step is not always necessary. Many dry-roasted nuts, such as peanuts and almonds, may be successfully chocolate-coated without glazing and with minimal subsequent oil migration. The presealing step, however, will provide an additional measure of protection, especially in very-high-fat ingredients, such as macadamia nuts.

If using a glazing step, the material selected should be noncrystallizing when dried. Typically, the glaze consists of a film-forming material, such as solubilized gum arabic. The confectioner may also use sugar syrup in conjunction with gum arabic and corn syrup to inhibit crystallization. In addition, some specialty dextrin materials, when combined with corn syrup, may make effective glazes.

To glaze the nuts prior to chocolate-coating, place them in a revolving pan and then apply just enough of the glazing solution to evenly wet them. Apply cool air (70? to 75?F) to thoroughly dry the glaze. Repeat this process several times until a suitable glaze has developed. At each application of glaze, the manufacturer must sufficiently dry the layer to ensure a stable product. In general, the layer must be just dry enough that it is no longer sticky, but not so dry that it flakes off -- knowing when to end the drying process comes mostly from experience.

Smoothing things over To begin the chocolate panning process, the confectioner places the nuts in the pan and starts the equipment. The chocolate does not need to be tempered but it should be cooled down to about 93? to 95?F. On a small scale, chocolate may be applied by hand with a ladle, but in a large operation, high-pressure spray equipment is most often used. These large setups are arranged with sprayers and cold airflow, both of which can be directed at the product as needed. For either method, apply enough chocolate to initially coat the nuts. The manufacturer must be careful to apply the chocolate onto the rotating nuts, not onto the walls of the pan. As the nuts tumble, the chocolate will begin to set, and pieces may start to adhere to each other. To counter this, apply cold air to harden the coating and keep the nuts freely flowing.

Once the nuts become free-flowing, the manufacturer can apply more chocolate. Continue this process of spraying and cooling until the coating reaches the desired thickness. Then allow the nuts to tumble freely, without the application of cool air -- frictional heat from the continued tumbling will slightly melt the surface layer of chocolate and contribute to a smooth coating.

When the nuts are adequately coated and smoothed, the confectioner may discharge them and place them into shallow trays. The panned nuts should set overnight at about 65?F -- this important step will allow a large fraction of the still-liquid cocoa butter in the chocolate to further crystallize and provide a rigid coating for the subsequent finishing glaze and polishing steps.

Finishing touches To protect the chocolate layer and enhance the appearance of the finished product, the manufacturer glazes the chocolate-coated nuts and polishes them with additional layers of sealing materials. Glazes for this step are similar to materials used for presealing the nuts -- usually a gum-arabic solution or a noncrystallizing dextrin and corn-syrup formulation.  

Like the glazing step for presealing nuts, the coated nuts go into a revolving pan and an adequate amount of the glaze is applied to the coated nuts. The nuts then tumble so the glaze can evenly spread over their surface. As the nuts start to stick together, applying cool air -- about 65?F and low humidity (45% to 50%) -- is essential to dry the water from the glaze and to maintain a rigid chocolate shell. This procedure continues until the layer thoroughly dries, but before the glaze begins to crack or peel.

An experienced panner will know by the sound of the tumble when the product is ready for another application of glaze. The glazing and drying processes will repeat several times, until a sufficient coat has built up on the product and the coating is well sealed. At this time, the confectioner may discharge the product, which rests in trays until it completely equilibrates, or may polish it directly.

To finish the chocolate-panning process, the confectioner applies a final layer of polish, often solubilized shellac. Shellac is the secretion of the lac insect that has been solubilized in denatured alcohol. The shellac coating provides a moisture-resistant barrier to the product, as well as an exemplary shine. Shellac modified with acetylated glycerides is preferable, as this will impart flexibility to the shellac film and prevent the coating from tearing off during the polishing process.

The panner applies just enough shellac to the product in a rotating pan to evenly wet it, and allows the product to tumble until the shellac is evenly distributed. Finally, applying cold air evaporates the alcohol solvent before discharging the product into trays.

If glazing and polishing are not desired, dusting the chocolate-panned nuts with cocoa powder or a blend of cocoa powder and powdered sugar provides an interesting alternative finish. Hard-panning chocolate-coated nuts with a hard sugar shell, used to make certain popular chocolate-peanut candies, is yet another approach to finishing off the product, although this involves additional steps to preseal the chocolate coat and to polish the sugar shell.

While round nuts are the most suitable for panning, odd-shaped nuts, such as cashews and walnuts pieces, may also be successfully panned. Enrobing and dipping are other means of chocolate-coating nuts. Whole nuts or pieces can even be molded into a chocolate bar as an inclusion. The confectioner should factor in the same considerations for designing product by these processes as for panning.

Filled fancies Another popular use of nuts in chocolate confectionery products is as a filling in a molded or enrobed chocolate piece. A very familiar product of this type is the chocolate peanut-butter cup. Other familiar nut pastes in chocolate confections are the almond-based marzipan, which in itself makes a fine confection, as well as hazelnut pastes, which chocolatiers have long blended with chocolate to make the classic Italian confection, gianduja. Hazelnut paste and oil can also be found in some European chocolates as anti-bloom agents.

One typical method to manufacture filled chocolate products involves forming the chocolate shell, filling it with a fluid or semifluid filling, and topping it with a sealing layer of chocolate. Chocolate-enrobed, nut-based confectionery fillings are also possible. In this type of product, a typical process may involve extruding the center, pre-bottoming the extruded piece with chocolate or compound coating, enrobing it with chocolate and then cooling it to set the chocolate coating. In a commercial scale, both of these processes are highly automated, ensuring a consistent, high-quality piece.

When working with fillings containing nut ingredients, the major problem again is oil migration. Nut fillings in shell-molded pieces will most likely be based on nut pastes such as peanut butter. The fillings must be fluid enough to allow them to be deposited into preformed chocolate shells. If the filling needs to be warmed for depositing, temperatures must not exceed that which would melt the already-set chocolate shell. Though this will vary for the specific processes, chocolates and fillings, the maximum temperature will generally be about 95? to 100?F.

Nut-paste-based fillings present several hurdles the confectioner must overcome. As indicated earlier, the naturally high oil content of common confectionery nuts makes oil migration a consideration during product development. Processing the naturally high-fat nut into a paste releases more oil, which makes it not only more available for migration in the confectionery system, but also more susceptible to oxidation.

Oil migration results in unappealing defects, such as loss of gloss and formation of fat bloom on the chocolate. Fat bloom occurs when fat crystals grow on the surface of the chocolate over time and results from improper tempering of the chocolate during processing, improper storage conditions or oil migration from other ingredients into the chocolate. It typically appears as a thin whitish or grayish film on the surface of the chocolate.

Oil migration also softens the chocolate surrounding the nut-containing ingredient. The oil in the center migrates outward toward the chocolate, and the oil in the coating moves toward the center until equilibrium in movement of the liquid oils is reached. Since the fats from nuts are mostly unsaturated, they are incompatible with cocoa butter, and in fact, will dissolve the cocoa butter in chocolate, creating a eutectic mixture where the solid-fat content of the combined fats is lower than either of the two fats independently. In chocolate-coated confections, a softening of the chocolate portion characterizes this eutectic effect.

Controlling the flow It is important to note that completely stopping the oil migration in a nut-chocolate product is usually impossible. The confectionery technologist's goal is to slow the oil migration through proper selection of ingredients, processing and post-manufacture handling.

The first factor to examine in control of oil migration is the chocolate used in the product. As mentioned earlier, a well-refined chocolate, owing to the smaller particle size of the solids, may offer more resistance to oil migration, since the small particles pack closer together.  

The chocolate must also be well tempered to maximize resistance to oil migration. A well-tempered chocolate will have finer crystallization of the cocoa butter; relative to a poorly tempered chocolate, the tighter pack of the small crystals will help prevent movement of foreign oil into the chocolate phase.

If the design of the confection allows, a thicker coating of chocolate will also help to minimize the effects of oil migration. In this scenario, the foreign oil must move through a physically thicker system to reach equilibrium with the chocolate shell.

Next, the filling formulation will need assistance to help inhibit movement of the nut oil from the filling to the chocolate. A very simple solution is to minimize the oil content of the filling, which is possible through the use of partially defatted nut ingredients, such as peanut pastes and almond meals. Specialty starches or dextrin-based ingredients can adsorb the free oil in nut fillings and therefore, make the oil   less available to migration.

Fighting fat with fat A more-common approach to protecting against oil migration is the use of specialty fats that will hold the mostly liquid oil in a matrix. These "structuring" fats can be palm oil or hydrogenated soybean and cottonseed oils designed to have a fatty-acid profile more compatible with cocoa butter. When crystallized, the structuring fat sets up in a network that can contain the nut oil. The nut oil is still fluid but slowed down because it is "entrapped" in a structuring fat matrix.

Technologists have also proposed processes for double-coating centers with a barrier fat to completely encase the center fat and separate it from the chocolate shell. This solution would suit an enrobed product more so than a molded product -- the process involving the latter requires numerous steps and would not be practical in a manufacturing environment. Barrier fats are typically specialty coating fats with a high solid-fat index and some compatibility with cocoa butter. Although this solution is technically sound, it is cumbersome. Barrier fats usually are only effective if the liquid-oil content of the filling is very low, typically less than 10%. The barrier coating must also be 100% complete -- the presence of pinholes or cracks will negate the effectiveness of the coating; and the coating fat must also not dissolve in the migrating oil and create a eutectic mixture, as mentioned earlier.

A compound coating compatible with the center fat also presents a worthwhile approach to control oil migration. Fats are available for compound coatings that may be more compatible with nut oils than cocoa butter. These coatings usually contain hydrogenated domestic oils, such as soybean or cottonseed, or tropical oils, such as palm, palm-kernel or coconut. In addition to being more tolerant to nut oils, these coatings have the added advantage of not requiring tempering prior to use.

The cold treatment Finally, storage is an important issue when addressing the problem of oil migration. Since the fats in nuts tend to be liquid oils, the more the oil is immobilized, the less the effect of migration will be. Lowering the temperature of the product during storage will aid considerably. Frozen or refrigerated storage of chocolate confections is not an uncommon practice; in addition to slowing oil migration, it will also delay the onset of oxidative rancidity.

Take care, however, when removing the products from cold storage -- wrap the product well and raise it to the desired sale or distribution temperature in stages to minimize condensation on its surface. Moisture condensation will lead to a defect called sugar bloom, where the moisture of condensation solubilizes the sugar in the chocolate; when the water evaporates, the sugar recrystallizes on the surface. Like fat bloom, this defect appears as a whitish crystal growth on the surface of the chocolate.

Inclusion strategies Another common use of nuts in confectionery products is as inclusions. Although smaller whole nuts, like peanuts, almonds and pistachios, can act as inclusions, nut pieces are usually more cost-effective than whole nuts. Familiar nut confections of this sort include caramel nut clusters, chocolate nut fudges, nut brittles and English-toffee-type products, nougats such as the classic Italian Torrone, and jellies, such as traditional Turkish delight.

When using a nut as an inclusion, oil migration and rancidity again are issues. In many cases, because the nuts are either cut pieces or whole, and not finely ground pastes, oil migration and oxidation will be less of a problem. However, in a product like nougats, where the cut surface of the nut may directly contact the chocolate coating, localized areas of bloom may appear as a result of oil migration. Again, a heavy coating of chocolate or double enrobing may help counteract this to a certain extent.

Another consideration with inclusions is matching the texture of the nut with the texture of the confection. For example, in a jelly product such as Turkish delight, a good choice would be a softer nut, like pecans, walnuts or pistachios. A harder nut, such as an almond, may present too contrasting of a texture when biting down on the piece, going from soft jelly to a hard nut. Similarly, with harder confections, such as toffee or brittle, a hard nut like almonds or hazelnuts will complement the crunchy texture of the candy.

Nuts can also act as a coating material on chocolate confections, providing visual enhancement, flavor and texture. Here, oil migration is less of an issue; although oil may migrate to the product inside, the effects are usually not visible. Rancidity, on the other hand, is an issue: The chopped nuts have more surface area exposed, and thus will be more prone to oxidation. In addition, cut nut surfaces may tend to dry out, leaving an unappealing whitish color on the surface. Appropriate packaging and storage of the finished product will go a long way in protecting its quality. Also, where appropriate, using nuts treated with antioxidants may provide protection against oxidative rancidity and offer extended shelf life.

Such a wide variety of nuts are available to the confectioner that a seemingly endless range of products is possible. Nuts can contribute flavor, texture, visual appeal and nutrition to any confection. In addition to those nuts most commonly used in sweets, the confectioner can consider other nuts or nut-like products, such as pumpkin seeds, sunflower seeds, pine nuts, soy nuts and even cocoa nibs. Knowing the potential issues when using nuts in a confection will enable the product developer to make delicious, unique, value-added candies with broad appeal.  

Peter Dea is a senior food technologist for Mattson & Co., Foster City, CA (www.foodcom.com/mattson), an independent developer of new food and beverage products. In addition to numerous years of product-development experience in confectionery and chocolate products, Dea has taught courses in confectionery and chocolate technology.

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