Cooling tunnels

Discrete pieces of product, such as peas, slices of carrot, beans and items of this size, can be conveyed on a perforated belt, with the cold air blasting up through the holes, to both cool the product and agitate it, to prevent it sticking either to the belt or to other similar pieces. This type of cooling tunnel is shown in Figure 19.1. 

The conventional cooling process involves a long and slow cooling of the product via cooling tunnels. Some experimental work has shown an average heat transfer coefficient around 20 W/m /K and an ambient temperature aroimd 11°C. A... 

In commercial practice, a defined cooling rate is delivered to the chocolate by the air in the cooling tunnel. Two sorts of approach were used. First, experiments used the values appropriate to the external cooling rate. As shown in Figure 22.1,... 

After forming, bulk crystallization is generally accomplished in a cooling tunnel (Fig. 3). Solidification proceeds through the deposition of triacylglycerols onto the... 

Fig. 3. Cooling tunnel. Product flow is from left to right. First zone is equipped with a "radiation plate" or heat sink.

Seguine, E.S., It Ain t Over Until...A Review of Post Cooling Tunnel Changes in the Cocoa Butter Phase of Chocolate, in Proceedings of the Annual Production Conference, Pennsylvania Manufacturing Confectioners Association, Hershey, PA, 1995, pp. 60-64. 

Massive chocolate products are deposited at 30-31°C into pre-heated (30-32°C) metal or plastic moulds. The moulds are then conveyed through a cooling tunnel where the temperature of the product is reduced to 8-9°C. The volume of the cocoa butter and chocolate shrinks during cooling and a contraction takes place which eases demoulding. 

Coating of food products is performed most frequently with emobers whereby food bars of the fun food category receive a layer of, for example, a chocolate mass (Section 6.4.2, Fig. 6.4-30b, items 13 and 14). This process is, however, not an agglomeration technique. Liquid coating mass is applied to the surfaces of the food article and solidified in a cooling tunnel. 

The basic candy-making principle is simply the boiling of sugar and the temperature to which it is cooked determines whether it will be a fondant (236° F [113.3° C]) or a toffee (300° F [148° C]). Today, candy manufacturing plants are equipped with every conceivable machine for each step in the manufacture of over 2,000 different kinds of sweets. There are continuous cookers, cooling tunnels, crystallizers, forming machines, chocolate coaters, and taffy-pulling machines. 

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