Basically, pre-mix beverage dispensers are containers with faucets. The container (bowl), usually made of a clear plastic, contains the liquid beverage. The faucet (spigot or contact lever valve) allows the beverage to be dispensed into the serving container.
There’s a method of chilling the beverage. Dispensers which employ ice for chilling are primarily used in locations where electricity may not be available, such as sports catering and picnics. The most common method of ice chilling is a central plastic column inside the beverage bowl. This can be fired from the top with crushed ice. Because the ice is separated from the beverage, there’s no dilution. However, the liquid beverage remains in contact with the ice-chilled column and stays cold. Unless the beverage is pre-chilled, this type of unit must be filled with ice and beverage for an hour or so before dispensing starts for the beverage to be chilled properly.
Another Method of Ice Cooling – The Cold Plate
This is a metal plate which contains tubing for the beverage to flow through on its way to the dispensing valve or faucet. Ice is placed in a compartment with the cold plate to provide the cooling.
The cold plate principle is sometimes used with mechanical refrigeration. In order to build a cooling “reserve” against peak hours, the refrigeration system freezes the cold plate in a layer of ice during slack periods when dispensing is light. The ice then provides a cooling reserve for peak periods when constant dispensing might overwhelm the capacity of the small mechanical refrigeration unit. The most common method of chilling a display dispenser is a mechanical refrigeration unit built into the base. In early models, such refrigeration compressors were quite noisy. Today’s units are often so quiet it’s difficult in a dining area of normal noise levels to determine when the compressor is running.
Because the pre-mixed beverage will often tend to separate if it isn’t kept in continual agitation, agitation is a feature of almost all non- carbonated display dispensers. There are two basic types of agitation. One utilizes an arm or paddle revolving slowly through the beverage to keep it mixed and aerated. The other uses a pump to spray the beverage to the top of the display container.
Advocates of the spray say this aerates the beverage more thoroughly, for a fresher flavor, and provides a better selling image. They also point out that with agitation and no spray there are “high water” marks on the bowl as the beverage level goes down. Such marks are especially visible when the beverage contains solids or pulp.
Advocates of the paddle say that it works better with thicker drinks and juices, which often slow or clog spray pumps. They also point out that spray systems promote oxidation, particularly affecting citrus juice flavors. Other beverages foam when sprayed.
You should determine whether the manufacturer of the beverage the operator plans to dispense from the unit recommends a particular type of dispenser. An additional feature offered on some units is a “foaming chamber” or “foaming head” where the beverage is vigorously agitated during actual dispensing. This whipping or spraying action causes the beverage to foam as its dispensed. Foaming produces a more attractive drink, gives it the semblance of being thicker, and highly aerates the liquid to enhance flavor. Dispensing in the typical pre-mix display unit is by gravity flow. The faucet or dispensing valve is at the bottom of the display bowl. The beverage simply flows by gravity from the bowl when the valve is opened.
Post-Mix Units Involve a Different Type of Dispensing
They use mechanical refrigeration to keep the beverage concentrate or base at the proper temperature. The concentrated juice or juice base is held in a refrigerated reservoir as a thick liquid. When the dispenser tap is opened, the dispenser combines the proper amount of beverage with a metered amount of water to produce the desired strength. The incoming water is also refrigerated by flowing through a mechanically refrigerated coil or cold plate.
Post-mix dispensers can be adjusted for the proportion of beverage/water mix. Manufacturers usually place this adjustment in a location where the casual employee cannot make changes. In some models, a special tool must be used to make the change.
This ability to change the mix is especially important in dispensers that can be used for frozen juice concentrates and frozen soft drink bases. The proper dilution ratio may vary from one type of juice or drink to another. For example, the dilution rate for lemonade concentrate is generally different from that of orange juice concentrate.
Some post-mix dispensers use a pressure-feed system. The pressure medium is usually compressed air. The air pushes the beverage through the system to the dispensing valve. This is particularly useful when the dispenser mechanism must be located below or away from the dispensing valve.