Home  Process plant - Enrobers

The majority of continous enrobers used for bakery foods are of the curtain or waterfall type, in which the product is moved through a vertical sheetlike stream of liquid chocolate. Bottoms are covered by other methods.
The usual sequence of operations in these machines is:

  • Properly conditioned coating from the tempering unit is delivered to the enrober as required;
  • Product is carried on a wire mesh or rod conveyor belt through a curtain of coating in an enrober unit consisting of, as a minimum, a jacketed coating tank with an agitator and flow pan, an agitator device for the take-away section of the conveyor belt, a water-jacketed heat exchanger, a bottomer, a detailer rod, and a blower; and
  • The pumps, piping, motors, and controls necessary for servicing the other equipment. An example follows; most of the details are applicable to other systems.

The coating tank and a drip pan extension, which together form an unitized machine, are made from continuously formed and welded stainless steel sheet. Surrounding this frame is a stainless steel air jacket. Thermo­statically regulated, electrically heated air circulates continuously within this jacket to maintain the temperature of the tank. During shutdown periods, the hot air system increases the temperature within the jacket to maintain the coating in a liquid state.

A stainless steel wire mesh belt with a 0.25 inch pitch conveys products through the coater. A shaker system adjustable in frequency and amplitude is provided to agitate the enrobed product. This vibratory action distributes coating more or less evenly over the product and also assists drainage of excess coating. The detailer rod is positioned at the end of the wire belt and rotates in a direction counter to belt movement. It can be adjusted up or down to eliminate trailing streaks of coating. Stainless steel flow pans allow a double curtain of coating to flow onto the belt. Melted coating flows either through a slit at the bottom of the pan or over one edge of the pan. The latter design is less likely to clog up. Pans can be designed to pour many evenly separated narrow streams of coating to stripe the product. Height of the pan can be adjusted in some models. Coating is pressure fed from the coating tank to a distributor that dispenses the melted material across the width of the pan. A chocolate coating machine enrobing marshmallow puffs.Beneath the belt, a bottoming pan receives the excess coating. A supply of coating is pumped into this pan when bottomed goods are being made. The belt carrying the cookies or other products across the bottomer is generally composed of thin metal rods or wires transversely disposed, and it travels just below the surface of the chocolate so that the coating will be able to contact the bottoms of the pieces. The pan can be moved up or down to affect the amount of coating applied. A bottoming roller can be fitted to the pan to pick up coating and apply it to the bottom of the cookie.
Excess coating is removed by a high-pressure blower system. A damper on the blower intake controls flow of air through the nozzles. The nozzle, which is a tubular plenum chamber, gives uniform air distribution across the width of the beIt. Nozzle height and angle, and width of air discharge, are adjustable. The detailer, a simple powered roller of small diameter located so as to contact the bottoms of the pieces, removes "tails" of coating which drop down from the product as it leaves the enrober belt.
The spray enrober uses a completely different method to apply confectionery coatings. It is based on using large orifice multidirectional spray nozzles through which the coatings are sprayed from the bottom and top onto the product to be coated. As contrasted with the standard enrobing curtain, this system has a large coating area that provides a very uniform coating at controlled rates on all surfaces. It is said that light, medium, or heavy coatings can be "dialed in" and uniform covering achieved. Enrobing speeds can be increased up to 50% it is claimed, compared to more conventional enrober designs. Energy savings are also possible, since up to ten times more coating is applied "to the product relative to the volume of coating being circulated.
Cooling Tunnels, Slabs, and Conveyors

Enrobed products must be promptly cooled to solidify the coating so the pieces can be packed and to put the fat crystals in a more stable condition. Proper cooling of a well-tempered coating will give a product having good gloss and firm texture, and the gloss and texture will be maintained throughout a long storage period. If the coating is not firm, it will smear or retain fingerprint impressions from the packing operation.
Cooling equipment for enrobed goods generally takes the form of a tunnel with refrigeration units to chill the air or surfaces and a conveyor belt to carry the products through the tunnel. Suppliers offer these tunnels in module form so that plants may assemble any desired capacity. In coun­ter-cooling tunnels, air temperature at the entrance should be about 65°F, and temperature should gradually drop until it reaches about 55°F at the discharge end. For more recently developed zone cooling tunnels, air tem­perature may be brought down from about 65°F at the entrance to 40°F near the middle, and then warmed up in the final zones to about 55°F so that the products are not cold enough to cause moisture to condense on them. Dwell time in the tunnel varies with products, but should be only a few minutes.
Contraflow cooling tunnels can consist of independently controlled cooling zones. They provide top cooling by radiation or linear convection and bottom cooling by conduction from a water-cooled slab. Zones are construc­ted from steel frames covered by insulated and reinforced plastic hoods that are removable for sanitation and complete accessibility to the conveyor and cooling module. Each section incorporates a water cooled table for bottom cooling. For top cooling, each section is split horizontally by a steel plate to form a supply return duct and product cooling area. The belt conveyor passes on top of the water-cooled slab through the product cooling area. Cooling air above the conveyor belt is horizontally distributed along the product zone against the product flow from the entrance of the tunnel to its middle and with the product flow from the middle to the tunnel end. Chilled water is circulated through the bottom bed and the cooling coils of each module. A radiation cooling system can be fitted, generally to the first third of the tunnel. Black-finished, water-cooled radiant panels are installed, replacing the steel sheeting above the product, and chilled water is circula­ted through them.
Cooling slab conveyors are used to cool and set bottoms of chocolate­ coated bakery products. They are simpler and cheaper devices than cooling tunnels. They normally receive products from the prebottomer unit and transfer them into the main coating machine. The conveyor bed is an assembly of steel plates. Serpentine channels are formed between the plates so cold water or other refrigerant can be circulated. There will be adjustable nose pieces at each end of the conveyor to assist in smooth transfer. The delivery and feed ends are hinged to facilitate connecting transfers.



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