Equipment for Tempering Chocolate Coatings:

Five construction features are said to be of great impor­tance to the tempering of chocolate so that there is perfect microcrystalliza­tion of the mass. These are
(1) many tempering sections,
(2) large cooling surfaces,
(3) perfect scraping and efficient mixing,
(4) cooling time, and
(5) accurate temperature control. If all these requirements are met, it is pos­sible to get a finished product with high deep gloss, fine-grained and crispy break, good keeping qualities, short solidification time, and maximum con­traction when cooled. For coatings, contraction is not much of a factor, because the product will not be removed from a mold, but there is some opinion that poor or inadequately controlled tempering can lead to spontaneous cracking of coatings, especially in products such as chocolate coated marshmallow deposits.

The initial handling of chocolate coatings will depend upon whether they are received from the supplier in melted condition or in slabs. There are melting devices specifically designed to reduce the solid chocolate to a fluid without causing any heat damage. In tempering, the melted chocolate must be brought through a number of temperature changes. These opera­tions can be applied in separate heat exchangers, but most large users will employ unitary assemblages designed to continuously perform the desired sequence of operations.

A commercially-available tempering unit is described as follows. The unit is a free standing, self-contained machine consisting of the tempering tube with its drive, a control panel, and a water system, all mounted on a fabricated steel framework with stainless steel covers. The unit requires supplies of cold water and hot water. Four standard sizes cover a through put range of 1,000 to 3,250 lb per hr. Capacity depends on the type of choco­late, milk chocolates requiring lower temperatures and longer hold times. The tempering tube is vertically mounted and divided into three sections: cooling, retention, and final temperature adjusting.

Using the tempering unit just described, untempered chocolate is continqously tempered during production. Liquid untempered chocolate is metered into the tempering tube where it is cooled in a swept film heat exchanger to a temperature at which stable beta crystals can grow. The chocolate then passes to the retention section, where these crystals grow and multiply. Without this retention time, it would be necessary to cool the chocolate to a much lower temperature in the first stage, and this could result in the growth of unstable crystals. As crystals multiply, there is an increase in mass temperature. In the last stage, another swept film heat exchanger is used to control the final temperature


to within 1.8°F of that required for the enrober.Chocolate holding tanks are of many different types and designs. A typical holding tank for use between the tempering equipment and the depositing machine might be comprised of a water-jacketed tank fitted with 11 stirrer and a vibratory sieve driven by independent motors.
The tank itself might be a welded steel trough with hemispherical bottom swept by a reci­procating stirrer: There will be a water jacket on the trough and exit pipe. The piping in these systems may be of black iron and must be wound with industrial heating cable and insulated.
Pumps recommended for chocolate systems are slow moving rotary displacement pumps. A typical pump would 'have two moving parts, a rotor on the main shaft and a pawl. These parts and the pump body are made from high grade cast iron. Rotors have one or two lobes. The former should be used only when delivering against minimum head pressure. Removable plates give ready access to the pump cavity. Seals are in cartridge form for quick removal and replacement.