The type of fat in a cookie and its coating should be compatible. When lauric and non-lauric fats are both used–one in the cookie and one in the coating–they repel each other and can result in fat bloom or a white film on the cookie’s bottom.

Photo courtesy of ADM Cocoa.

Formulation challenges

“The most important things for bakers to watch out for is that they are tempering the chocolate correctly, and that the product being enrobed is at the correct temperature,” Kazmierczak says. “A lot of times I'll go to bakeries and they'll be enrobing something that is above 90°F. I always try to say 70°F or less for chocolate or compound coatings.” At the same time, it's important not to enrobe frozen product. This can affect not only the temper, but also as the frozen product begins to thaw, you may run into cracking issues.”

Another important aspect to monitor is the cooling temperature. “With compound coatings, you want to shock it with 45°F to 50°F temperatures with high air velocity, whereas with chocolate you want to ease into the cooling with lower air velocity. If you cool chocolate too quickly you will run into cracking issues,” Kazmierczak says. Products should spend about 10 minutes to 15 minutes in the cooling tunnel depending on the amount of coating applied to each product. Storage temperature and distribution conditions also are important to monitor. “A lot of times bakeries are much hotter than a regular confectionary company. As long as you have the finished product held between 60°F and 70°F with less than 60 percent relative humidity, you're making sure that the shelf life is intact,” he adds.

Fat bloom and sugar bloom are two challenges that both chocolate and compound coatings can encounter. Blooming of chocolate is the most common problem, notes Besin. Sugar bloom is caused by moisture condensation from ambient air or moisture migration from the product. This occurs when the temperature of the product's surface as it emerges from the cooling tunnel is much different from the temperature outside the cooling tunnel. As a result, microscopic condensation forms on the product. “This micro water will melt the sugar inside the chocolate, resurface on the top and solidify, so you'll have a slightly whitish and grainy film on the surface of the chocolate,” Besin says. Sugar bloom feels grainy to the touch.

Fat bloom, or fat migration from the baked product into the coating, can occur as a result of poor tempering, poor warehousing, distribution or handling conditions or when incompatible fats are used together. Fat bloom can be recognized as a white film on the bottom of a product. If a cookie is made from a cottonseed oil (a non-lauric fat) shortening and that cookie is covered in a coating made with palm kernel oil (a lauric fat), the two fats will reject each other. Lauric and non-lauric fats are incompatible and will only tolerate 3 percent contamination from the opposite group, Besin notes. In the above scenario, it would be better to choose a cocoa butter coating, which is a non-lauric fat to complement the non-lauric cottonseed oil in the shortening. An issue also can arise if a cookie with a non-lauric coating is baked on a belt treated with a lauric release agent. In this case, the bottom of the enrobed cookie may develop fat bloom because of the contamination between the lauric and non-lauric fats.

Other issues that can occur with coatings include a waxy or greasy texture to the coating. Non-lauric fats tend to be more greasy than lauric fats because of the melt profile. The higher the melting point, the waxier the chocolate compound coating becomes. Sometimes, a high melt point is important. “We have different melt points of coatings that range from 93°F to 118°F, so a lot has to do with what type of heat resistance you're looking for at the end,” Kazmierczak notes. “We sell some products to New Mexico and South America, which have a 108°F plus melt point on them because they're sitting on shelves and in storage where the normal temperature is 75°F to more than 80°F. If the melt point is higher, it will be waxier, but we use higher melt points to combat those higher temperatures.”

The first step to overcoming challenges when formulating with coatings is to begin working closely with a supplier during the development phase. Be sure to discuss the melt point, viscosity of the coating and type of fat to use in the coating, and share the details of your application, production process and baked item formulation, so the supplier can help provide the correct coating for the application.

Making a coating

To make a coating, the raw materials are first weighed into the mixer. Then the mixture goes through a pre-grinding process, which reduces the large sugar particles by rolling them between two cylinders. The next step is the refining process where the cocoa solids and sugar crystals are refined further between 20 microns to 30 microns. If the coating is refined too much below 15 microns, it can become gummy.

During the refining process, color and flavor are modified and moisture decreases, says Laurent Besin, technical services and applications manager North America, Barry Callebaut USA LLC, Chicago. After refining comes the conching process, which brings out the flavor, aroma and texture of the chocolate. This happens in two stages. First, dry conching (before cocoa butter or lecithin is added) develops flavor and coats the solid particles with fat. Next, liquid conching (after the cocoa butter or emulsifier is added) achieves the desired rheology, the temperature rises, the flavor develops and the humidity decreases. If a baker requested a liquid delivery, after the second conching stage, the chocolate is pumped into a tanker to be delivered. If a bakery requests solid chocolate, the supplier pumps the chocolate to its moulding facility. Chocolate then needs to be tempered to achieve the correct crystal form in the cocoa butter and to give the mixture its shiny appearance; compound coatings can skip this step because the fat systems do not require tempering. Finally, the chocolate is cooled and packaged. When the shipment arrives at the bakery, the baker must melt the chocolate and temper again.