Secrets of Chocolate and Confectionary Coatings 36623

ELEMENTS

Secrets of Chocolate and Confectionary Coatings

By Peter Dea
Contributing Editor

In our industry of ever-changing trends, designing products that appeal to a broad range of consumers is always challenging. Chocolate as a food ingredient, however, is one item that never seems to go out of fashion. Conveying an image of quality and indulgence, few ingredients offer such versatility in both flavor and functionality.

With all the positives about chocolate, a food-product developer needs to be familiar with what chocolate is and how to work with it. Also, when development parameters do not allow the use of real chocolate, it is just as important for developers to be familiar with alternative products to chocolate and to understand the reasons for selecting one alternate over another.

Setting the standard

In the United States, FDA has established very specific requirements for the different classifications of standard-of-identity chocolate each with certain levels of cocoa solids and milk solids which must be met. For example, sweet chocolate requires a minimum of 15% chocolate liquor and no more than 12% dairy solids, while bittersweet and semisweet chocolate raises the minimum chocolate-liquor content to 35%.

The federal regulation also requires that the only fats in standard-of-identity chocolate products are cocoa butter and dairy fat. If the product uses other fats, it does not comply with the U.S. standard and cannot be labeled as chocolate. This differs from standards of the European Union, which permit up to 5% of certain vegetable fats in a product labeled as chocolate. The U.S. regulations do have separate standards for products containing cocoa butter and other vegetable fats and allow them to be labeled, for example, as chocolate and vegetable-fat coating.

Solid foundations

Chocolate is a suspension of solid particles in a fat phase. The United States only allows fats from cocoa butter and dairy-butter oil. Cocoa solids and nutritive carbohydrates, such as sucrose, comprise the major solid particles. Optionally, dairy solids, such as milk powders and any other flavors, might be included if they do not imitate chocolate, milk or butter flavors.

Cocoa solids provide the distinctive flavors identified as chocolate, which originate from the fermented, roasted beans of the cacao tree. Although many factors contribute to the flavor of a chocolate, the cocoa solids establish the foundation for the flavors that will eventually evolve during the manufacture of chocolate.

Cocoa beans are predominantly harvested from the West African regions of the Ivory Coast, Ghana and Nigeria. Other significant regions include South and Central American areas of Brazil, Venezuela, Ecuador, Guatemala and Mexico. Southeast Asian regions in Malaysia and Indonesia also are important suppliers of cacao.

Although recently it has been popular to produce so-called varietal chocolates, made with beans of a single region, most industrial chocolates are made from blends of bulk beans and flavor beans. Beans from different growing regions might have their own characteristic flavors, as well as varying melt points of their cocoa butter. West Africa, the primary supplier of cacao, supplies the basic bulk bean feedstock of the chocolate industry. Processors commonly blend these beans with complementary flavor beans from other cacao growing regions, such as Venezuela or Ecuador, to define the final flavor of a particular chocolate recipe.

Cocoa beans are the seeds of the cacao pods. Mature pods are harvested and the seeds removed, along with the pulpy interior. The beans and the pulp mass are exposed to naturally occurring microflora of the areas, initiating the fermentation. It is not actually the beans that undergo the fermentation, but the pulp mass surrounding the beans. Fermentation is a critical and a complex part of chocolate flavor development, requiring about five to six days. During this cycle, many chemical reactions responsible for the characteristic flavors identified with chocolate occur.

After proper fermentation, the beans are dried. At this point, the beans, although fermented and dried, still have a raw, harsh taste. The dried beans are cleaned of foreign material and then roasted to further develop the flavor of the chocolate. Depending on the manufacturer, the beans may be roasted in the shell and then cracked to remove the shell or the beans may be treated with an initial heating to facilitate removal of the shell, broken to a uniform size and then roasted with the final heat treatment.

Conditions for roasting vary greatly and depend on the type of bean, the process and equipment, and the intended finished product. For example, overroasting of nibs will result in burnt, acrid or bitter flavors. Under-roasted nibs will result in raw, green or beany flavors. Chocolate made with such beans will typically lack chocolate flavor, as well. General temperature ranges might be about 230°F to 260°F, but the desired flavor and aroma is necessarily a combination of time and temperature of the roast. Only after roasting do the beans finally begin to develop the familiar flavors and aromas that we identify as chocolate.

In milk-chocolate products, dairy solids provide the next major source of solids in the chocolate. While in semisweet chocolates, the cocoa solids play the major role in flavor impact, with milk chocolates, the dairy ingredients contribute their own, unique flavors. Depending on the type of milk solids used, the flavor profiles might differ. The most-common sources of dairy solids include spray-dried wholemilk powder, skim-milk powder and milk-chocolate crumb. According to Rick Schwartz, technical manager, Peters Chocolate, Lititz, PA, milkchocolate crumb is a vacuum-dried, crystallized mixture made from milk, sugar and chocolate liquor, and produces a milk chocolate with a rich, creamy and caramelized flavor. Unlike the crumb process where the sugar and milk proteins undergo a relatively slow and controlled caramelization, little, if any, caramelization occurs under the flash-evaporation conditions of the spray drying process. While spray dried milk has some cooked-milk characteristics, it has none of the caramelized flavor found in crumb, he says.

Liquid gold

The predominant fat of chocolate is cocoa butter, a component of the cocoa bean. Cocoa beans have a naturally high fat content, containing about 53% to 55%. Once cocoa beans have gone through the process of fermentation and roasting, processors grind the nibs to a product called chocolate liquor, or unsweetened chocolate. The degree of fineness during this grinding process varies depending on the intended use of the liquor, but the purpose is to reduce the particle size of the cocoa solids to that approaching the finished chocolate. Grinding the nibs also breaks down the cellular structure, which releases entrapped cocoa butter. Optionally, the liquor might be pressed to extract the golden cocoa butter, leaving cocoa solids for the manufacture of cocoa powder. The extracted cocoa butter is filtered of residual fine cocoa particles to yield the golden liquid fat that can be directed to the chocolate manufacture stream.

As stated earlier, other than cocoa butter, butter oil is the only other fat that standard-of-identity chocolate can contain. Besides contributing to flavor, butter oil is also functional. Schwartz explains, Anhydrous milk fat added to semisweet chocolate results in some resistance to fat bloom. Fat bloom, the growth of fat crystals on the surface of the chocolate over time, results from improper tempering of the chocolate during processing or improper storage, it appears as a white or gray film on the surface of the chocolate. The addition of milkfat also changes the melting properties and flavor release. Generally, this softening effect is appraised as an improvement, he adds.

Because cocoa butter has a sharp melting point of about 93°F to 98°F, or slightly below body temperature, it melts in the mouth when consumed, leaving no lingering fat residue often described as a waxy tail. Part of the allure in the chocolate-eating experience is the luxurious melt-in-your-mouth characteristic, which conveys a sensation of decadence and indulgence.

Smoothing things over

Having produced suitable chocolate liquor through fermentation, roasting and grinding, one can combine the liquor with the other permitted ingredients for chocolate. As mentioned earlier, nutritive carbohydrate sweeteners, dairy solids and other flavoring ingredients constitute the other solid particles in this fat-suspension system. In fact, one could combine chocolate liquor and regular sugar and the product might meet the requirements of the federal standard for chocolate. However, this product would taste nothing like the smooth, flavorful product weve all come to expect.

Industrial chocolate manufacture combined chocolate liquor with sugar and optional dairy solids, which refines the combined mass to further reduce the particle sizes of the solids, and then subjects the refined mass to a process called conching.

The refining process reduces the physical size of all the solid particles in the mass to produce a finished chocolate with a smooth mouthfeel, and to further release cocoa butter from the cellular structure of the cocoa solids. Without proper refining, the chocolate texture would be coarse and gritty. While particle sizes will vary depending on the desired finished effect, a typical good-quality chocolate might have a particle size of 25 to 30 microns. A high-quality chocolate might have a finer particle size of 15 to 20 microns to deliver a very smooth mouthfeel. In some instances, depending on the application, a somewhatgritty texture might not matter. For example, in a chocolate chip, as Schwartz explains, the texture will be coarser because they are mainly used as inclusions in cookies, where a small degree of grittiness might not be apparent.

Conch time

Following refining, the manufacturer will conch the combined mass of chocolate liquor and other solids particles. The primary purposes of this mysterious process are to remove residual moisture and undesirable volatiles, such as organic acids, to aerate the chocolate mass for flavor improvement, and to fully distribute the cocoa butter over the solid particles. In very simplified terms, conching takes place in a heated vessel with agitation. Conching times and temperatures, like roasting conditions, are highly variable and most manufacturers regard them as the trade secrets.

When a chocolate mass enters a conche, typically it will be very dry and stiff. As the mass is agitated in the conche under heated conditions, moisture, which may be suspended in the mass, will eventually evaporate away. Removal of moisture reduces viscosity, bringing the mass to a much-more-fluid condition. Concurrently, as moisture is being removed, other volatiles, such as acids and other organic compounds, are also driven off, removing much of the harsh, sharp flavors that might have originally been part of the chocolate liquor. Aeration of the mass also results in oxidation of polyphenolic compounds, improving the chocolate flavors. Finally, the agitating action of the conche will help disperse agglomerations of solid particles, resulting in singular cocoa-butter-coated particles and a smooth-textured product.

Close to the end of the conching cycle, processors add any remaining required cocoa butter to meet the specifications of the formula and to adjust to the desired final viscosity. They will also add lecithin, which helps reduce viscosity, at this point. Although the fat content of chocolates will vary depending on the finished application, most chocolates have between 28% to 33% total fat, with the actual fat level paralleling the need for a lower or higher viscosity.

Schwartz explains: It is possible to formulate a semisweet chocolate with the same ingredients, but at different percentages that could be used both for enrobing and for chips. Enrobing is the mechanical method of coating centers with chocolate by putting them though a curtain of tempered chocolate. To achieve uniform coverage, and the target weight gain, the chocolate must have the proper flow characteristics. To achieve this, enrobing chocolate typically has a viscosity of 10,000±2,500 centipoise.

Drops or chips are conical in shape and are deposited through small nozzles. To maintain the cone shape, a viscous chocolate must be used with a typical viscosity range of 50,000±10,000 centipoise. Note the great difference in viscosity values for the two types of chocolate, even though they might contain the same basic ingredients. Semisweet chocolate used to produce drops will contain less cocoa butter and more sugar than an enrobing chocolate, he adds. After this very time-intensive process of fermentation, roasting, refining and conching, we have finally produced a product that we can identify as chocolate. Making the chocolate up to this point is only half of the goal, however. While some characteristics of cocoa butter contribute to chocolates desirable eating qualities, others make its ease of use somewhat elusive.

The shape of things to come

Although the manufacturer has up to this point taken great care to produce a very high quality chocolate coating, it is still in a liquid form, and not suitable for the finished product. Although chocolate might be transported in liquid form to the end user, it must eventually be solidified to its final form in the finished food product. Because of the unique way cocoa butter crystallizes, processors must employ a special process called tempering.

Cocoa butter is a polymorphic fat, meaning that, depending on the conditions of the crystallization process, the fat can crystallize in up to six different forms. Of these six forms, for practical purposes, only one, the beta (ß) crystal (also known as form V), is stable. The goal of the tempering process is to induce crystallization in the correct quantity of the cocoa butter into this stable beta form. Additionally, the beta crystals should be small to give a fine crystal structure throughout the chocolate, resulting in the high gloss and sharp snap characteristic of well-tempered chocolate.

Molten liquid chocolate left to crystallize on its own at room temperature will eventually crystallize into the beta prime (ß') form, one of the unstable crystal forms. ß' crystals form at 60°F to 82°F and melts at about 83°F. Because of this rather low melting temperature, chocolate in the ß form, when handled, feels soft and sticky. As this ß' form is unstable, it will eventually transform to the stable beta form over the course of up to 30 days. However, since the fat was crystallized without any nucleation, the final crystal structure will be very coarse, the texture very crumbly and the appearance, mottled and unappealing.

While there are several ways to temper chocolate, the general ideal is: Melt the chocolate out to remove any crystal forms, then cool the chocolate to a temperature too high for unstable crystals to exist, yet low enough that the stable beta crystals can form and remain in place. The presence of the right amount of stable beta crystals in the liquid mass will eventually crystallize the remaining liquid cocoa butter to the same beta form during the subsequent cooling process. Typically, modern tempering machines cool the molten chocolate mass to a temperature favoring beta formation and, combined with shear, result in formation of the right quantity of fine beta crystals. Another method is to use already-tempered chocolate pieces, or shavings, to act as nucleating seed for the rest of the chocolate mass. As the tempered chocolate already is in the correct beta form, the remaining molten chocolate will crystallize likewise in the same form.

Once the liquid chocolate has been properly seeded with the correct beta form, the chocolate is in temper and can be used. Processors might use an enrobing coating over another food product, such as a cookie or candybar center, or the chocolate might be molded into solid pieces. At this point, care must be taken to ensure the chocolate is cooled properly.

Temperatures used to cool the chocolate must be low enough to set the remaining cocoa butter in a reasonable length of time, but not so low that unstable ß' crystals are induced. Cooling tunnels for chocolate application are designed to initially cool the chocolate under very gentle conditions. For example, 65°F to 70°F promotes the crystallization into the form provided by the beta nuclei. Gradually, the temperature is lowered to about 60°F to 65°F in a second zone of the tunnel with more-vigorous forced-air cooling to remove latent heat generated by the crystallizing fat. A third zone, with evenlower temperatures, might also be used to fully set the remaining fat. The exit temperature must not be lower than the dew point of the room temperature; this would form condensation on the exiting chocolate pieces. If condensation forms on chocolate, the moisture will solubilize the sugar in the coating. When this moisture evaporates, the sugar recrystallizes on the surface leaving a defect known as sugar bloom. Its appearance is similar to fat bloom (a white or gray film) but will be rough to the touch.

Sugar-free chocolate coatings, to an extent, fall into a unique category. They can be made with the same chocolate-liquor and cocoa-butter ingredients as regular chocolate. However, since the standard-of-identity does not categorize polyols, the bulk sweeteners used in these coatings, as nutritive carbohydrates, it prevents them from being labeled as chocolate. John Urbanski, vice president, technical sales and services, Peters Chocolate, explains: Polyols like maltitol, lactitol and erythritol are commonly used sugar substitutes. The manufacture of sugar-free products is typically done on the same processing equipment as conventional chocolate.

However, Urbanski cautions: Unlike the sucrose in conventional chocolate, most polyol sugar substitutes are somewhat more temperature sensitive, which means that lower temperatures are employed in their production and eventual use. Sugar-free products are not typically conched to any significant degree because of this.

Compounding the situation

Historically, the industry developed compound coatings as a cost effective alternate product to address the traditionally cost-volatile cocoa market. Like chocolate, compound coatings are suspensions of solid particles in fat, but the fat now comes from vegetable fats other than cocoa butter. Because compound coatings are intended as alternatives to chocolate, they must, to an extent, behave similar to chocolate. But when possible, it also makes sense to have properties that outperform chocolate.

In general, compound-coating fats are divided into two broad categories: domestic fats and tropical fats. Domestic fats are typically derived from North American crops, such as soybean and cottonseed, while tropical fats are derived from coconut, palm fruit and palm kernel. Collectively, these fats are described as either cocoa-butter replacers or cocoa-butter substitutes. Compound coating fats can also be further categorized as lauric and nonlauric. Lauric fats are so termed because they have high levels of the 12-carbonlength fatty acid, lauric acid.

According to Urbanski: Cocoa butter replacers, are typically nonlauric fats with relatively steep melting curves. They require little, if any, temperature conditioning prior to use, but are generally harder and waxier than cocoa butter. Cocoa butter substitutes are typically lauric fats with relatively steep melting curves and more closely mimic the sensory properties of cocoa butter. They present good eating qualities, require little temperature conditioning prior to use, but typically have shorter shelf lives and are prone to bloom, to a certain extent, like cocoa butter.

Other exotic tropical fats used for these products include shea-nut butter, mango-kernel butter and illipe butter, which are the raw materials of the cocoa-butter-equivalent fats. Cocoa butter equivalents have physical properties that are nearly identical to cocoa butter and, like cocoa butter, require complete tempering to set in an optimal condition, Urbanski elaborates. These types of fat can be used in total to produce nonstandard chocolate-compound coatings or might be combined with real cocoa butter and chocolate liquor to produce coatings meeting the standard of identity for chocolate and vegetable-fat coating. However, such products are rare as they are perceived as inferior and offer no advantage in ease of use compared to chocolate.

Both domestic and tropical classes of cocoa-butter replacers and substitutes might be produced by fractionation and hydrogenation of the basic feedstock oils. Manufacturers often combine both processes to produce fats with similar performance and eating qualities to cocoa butter. Although hydrogenated fats might offer some benefits in performance in the finished coating, with todays consumer awareness of the negative impact of trans fats and the negative label perception of hydrogenation, fractionated lauric fats from palm fruit and palm kernel are in higher favor.

Interest in compounding

Manufacturing compound coatings mirrors the process of chocolate manufacturing to a degree. Dry ingredients, such as cocoa powder, sugar and dairy solids, are blended with the selected fat and refined to the desired particle size. The refined mass is then conched, albeit typically for shorter times than chocolate. Fat and viscosity are subsequently adjusted, and the coatings then solidified into pieces, or, like chocolate, delivered as liquid coatings.

Virtually all of the cocoa-butter replacers require no tempering and will crystallize directly into a stable ß' form, a major advantage over real cocoa-butter coatings. Typically, the liquid coatings are cooled to slightly above the melt point and used as
desired. Compound coatings, typically allow for faster throughput as they can tolerate lower cooling-tunnel temperatures and more-vigorous, forced-air cooling. Compound coatings, in fact, perform best with fast-shock cooling. This quick crystallization of the fat directly into a stable ß' form results in a coating with a high gloss and fine crystal structure.

Despite the advantages being nontempering, having quick crystallization and costing less, compound coatings have several disadvantages when compared to the gold standard of chocolate. Note that the ingredients of a chocolate-flavored compound coating typically include cocoa powder rather than chocolate liquor. This is not only because of lower cost, but also as a result of an inherent incompatibility between cocoa butter and cocoa-butter replacer fats.

Because fatty-acid profiles of oils used for these cocoa-butter replacers are very different than the fatty-acid profile of cocoa butter, it comes as no surprise that these fats are not very compatible. Coatings made with lauric fats have very low compatibility with cocoa butter, typically tolerating 4% to 5% of the fat phase as cocoa butter. Excessive cocoa butter in lauric-based coatings results in a eutectic effect, creating a soft texture and fat bloom in the coating.

Because of this low tolerance for cocoa butter, chocolate liquor as an ingredient in compound coatings is generally not an option. Although some domestic nonlauric fats can tolerate up to 20% cocoa butter and would permit the use of some chocolate liquor, since many compound coatings are formulated to be low cost, it does not make economic sense to use such an expensive ingredient in a low-cost product. Additionally, the negative image from the use of hydrogenated fats in these cocoa-butter-tolerant fats might limit their acceptance.

Despite these shortcomings, compound coatings are extremely important as alternatives to chocolate coatings. Although flavor expectations might fall short when it comes to chocolate-flavored compound coatings, they offer more versatility with other flavors. Unlike cocoa butter, which has a very distinct flavor, vegetable fats used in compound coatings have very mild, bland flavors and offer the developer a clean palette to design the flavor of the coating as desired. The light, white color of compound-coating fats also enables production of coatings of a wide range of colors.

Compound coatings tend to be more cost-effective as an ingredient, as raw-material costs for most compound coatings tend to be lower than the commodities of the volatile cocoa market. Because there is no standard of identity to meet, manufacturers have the liberty to design a coating to meet the needs of a particular application, rather than to meet the needs of a legal definition. As an example, the availability of the fats with higher melt points enables production of coatings that might have more tolerance to higher temperature conditions, which might not be possible with cocoa butter.

In other instances, coatings might need to be more physically flexible than real chocolate. Chocolate contracts strongly and becomes very brittle when crystallized. As a result, this coating can crack and flake off easily from an enrobed soft substrate, such as a cake. Compound coatings designed for soft bakery products will have softer set with minimal contraction to improve handling and eating qualities.

Compound coatings might offer better performance in terms of oil migration. Chocolate-covered products with high fat contents, such as truffle centers or nut centers, will always exhibit signs of oil migration over the shelf life of the product. Oil movement from the center of the product to the surrounding chocolate coating might manifest itself as softening of the coating or development of fat bloom on the coating. This defect is not limited to chocolate coatings and can also occur with compound coatings. However, selection of a compound coating with a fat composition similar to that of the center material might help minimize the effects of foreign oil movement, an option often not available with chocolate. Chocolate and compound coatings offer a wide range of possibilities for new-product development. Real chocolate delivers a premium in flavor, image and quality. Compound coatings offer much of the functionality of chocolate and, in many cases, greater versatility. Rarely is a discussion of sweet applications complete without the mention a chocolate option as part of the product lineup. For the product developer, a sound understanding of what confectionery coatings are and how they behave will lead to an understanding of which coating best suits the intended application.

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