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Applying fat-based coatings to a bakery product is often an excellent, though costly, way of increasing consumeracceptance of the item. These coatings are frequently applied to cupcakes, swiss rolls, doughnuts, and cookies, and canalso be found on many other products. They have even been applied to pretzels, crackers, croissants, fried pies, and other unlikely candidates for this treatment. The highest quality fat-based coatings are the true chocolates, such as milk chocolate, but these are usually too expensive for use on baked goods for the general market. Analogous coatings with little or no chocolate content are available and are quite satisfactory in most cases. The chief problems encountered by
users of these coatings are cost, difficult processing requirements, and susceptibility of the coatings to damage by ordinary ambient temperatures. In the following section, proces­sing requirements and how they can be met by existing commercial equip­ment will be discussed.
Need for Special Treatment of Chocolate

Enrobing lines for applying fat-based, essentially moisture-free, coatings to small baked goods are common in the baking industry. Choco­late-flavored coatings are the most common, but other types such as white vanilla or pastel-colored coatings of different flavors (e.g., strawberry) are also available. Coatings containing vegetable fats other than cocoa butter are usually called compound coatings and they have substantially different properties than coatings containing real
chocolate. Manufacturers of edible fats have spent much research time and money in trying to duplicate the organoleptic properties of chocolate with coatings that are cheaper and which do not have the temperature sensitivity of cocoa butter, but complete success has not been achieved.

In the enrobing process, the cooled baked items are carried from a textile or plastic conveyor belt on to a wire-mesh belt that is an integral part of the coating machine. The metal belt conveys the product through a curtain of liquid coating that covers the top and sides of the articles. A roller, under the belt coats the bottoms of the pieces. A tank holding a supply of tempered coating is located nearby, often under the coating machine. A pump circulates the coating to a flow pan which
forms the curtain by allowing the liquid to. flow over one side of the pan. An air blower removes excess coating from the product, and helps to intensify the gloss, but it may leave slight ripples on the product. A vibrator shakes a section of the mesh conveyor belt and smooths out some of the ripples on the coating. The detailer rod (anti-tailing device) helps to control the amount of coating on the bottom and removes strings and tails. Enrobing bakery goods with chocolate-containing coatings presents a number of problems not encountered in other finishing operations. Obtain­ing and retaining optimum texture (mouthfeel) and appearance of chocolate coatings depends upon carefully following a prescribed course of tempera­ture treatments. This "tempering," as it is called, is very intolerant
to temperature fluctuations outside acceptable ranges. Furthermore, products covered by even the best tempered coating will be irreparably damaged by exposure to temperatures above about 95°F-the exact temperature depen­ding somewhat on the composition of the coating and the time of exposure.

All of these problems arise from characteristics of the fatty sub­stances making up about 50% of pure chocolate. Melted chocolate liquor (also called bakers chocolate, bitter chocolate, and pure chocolate) is made up of a continuous phase of cocoa butter and a dispersed phase consisting of very fine particles of the nonfatty portions of the cocoa bean. When mixed with sugar, milk fat, or other components of coating chocolates (sweet choco­late, semi-sweet chocolate, milk chocolate, etc.) the basic system of continu­ous phase fat and discontinuous phase (everything not soluble in fat) per­sists. On cooling, the liquid chocolate behaves largely according to the crys­talline status of the  fat in this continuous phase.

The fat can crystallize in many forms, only one of which (called the beta form) is stable. The unstable crystalline forms, if present, will revert in time to the stable form, but pro­ducts manufactured from chocolate containing these unstable forms will be of poor appearance, suffer from fat bloom, and (in the case of molded pro­ducts) be difficult to extract from molds due to reduced shrinkage. The pur­pose of tempering is to first remove the unstable forms by melting the choco­late and then to form a maximum percentage of stable crystals by cooling the liquid chocolate slowly according to an appropriate schedule. In an ideal situation, only the beta crystals will be present in the finished article.

If the tempered chocolate is placed on a hot product, all of the preceding effort will go for naught. Baked items should reach the enrober at a temperature of 75° to 85°F, and the room in which the enrober is located should be at the same temperature. The coating, after having been subjec­ted to the tempering process, should be maintained at the appropriate holding temperature, which for pure chocolate is 90°F. Compound coatings which may include cocoa but normally do not include chocolate, may either require or not require tempering, depending on their composition.


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