Premix and postmix (also post-mix) are two methods of serving – usually carbonated

Carbonation

Carbonation is the process of dissolving carbon dioxide in water. The process usually involves carbon dioxide under high pressure. When the pressure is reduced, the carbon dioxide is released from the solution as small bubbles, which cause the solution to "fizz." This effect is seen in carbonated...

 – soft drink

Soft drink

A soft drink is a non-alcoholic beverage that typically contains water , a sweetener, and a flavoring agent...

s that are alternatives to bottle

Bottle

A bottle is a rigid container with a neck that is narrower than the body and a "mouth". By contrast, a jar has a relatively large mouth or opening. Bottles are often made of glass, clay, plastic, aluminum or other impervious materials, and typically used to store liquids such as water, milk, soft...

s and can

Can

Can may refer to:-Container:* Aluminum can* Steel can, an airtight tinplate container for storing food and other predominantly liquid products* Beverage can, a can designed to hold a single serving of a beverage* Oil can...

s.

Premix

Premix refers to a ready-mixed, ready-to-drink

Ready to drink

Ready to drink is a term used to describe a packaged beverages that is sold in a prepared form, ready for consumption.The term is typically used to contrast packaged forms of beverages that are also sold in forms that require preparation, for example iced tea and alcopops Ready to drink (often...

 soft drink that has usually been packaged in 5-gallon stainless steel

Stainless steel

In metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass....

 tanks. The premix itself is identical to the beverage of the same brand that is sold in bottles or cans, and is already carbonated. The soft drink is passed through a premix dispenser that refrigerates it before dispensing it through a pressure-compensating valve or tap.

A premix dispenser is suitable for outlets that regularly sell the particular soft drink, but in relatively small amounts.

Carbonation tester

At the plant, a quality control

Quality control

Quality control, or QC for short, is a process by which entities review the quality of all factors involved in production. This approach places an emphasis on three aspects:...

 manager periodically checks the carbonation level of the premix tanks with a carbonation tester before shipment.

Postmix

Postmix refers to the system in which a syrup

Syrup

In cooking, a syrup is a thick, viscous liquid consisting primarily of a solution of sugar in water, containing a large amount of dissolved sugars but showing little tendency to deposit crystals...

 (concentrate) of the soft drink is shipped to the retailer, usually in a returnable tank or a disposable bag-in-box

Bag-In-Box

In packaging, a bag-in-box or BiB is a type of container for the storage and transportation of liquids. It consists of a strong bladder , usually made of several layers of metallised film or other plastics, seated inside a corrugated fiberboard box. The bag is supplied to the 'filler' as an empty...

 container. At the point of sale, the soft drink is mixed to order from the postmix syrup, chilled and purified water

Purified water

Purified water is water from any source that is physically processed to remove impurities. Distilled water and deionized water have been the most common forms of purified water, but water can also be purified by other processes including reverse osmosis, carbon filtration, microfiltration,...

, and carbon dioxide

Carbon dioxide

Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

(from a gas cylinder), and usually served directly from a gun-type nozzle.
A postmix dispenser is a more sophisticated device than a premix dispenser. The postmix system is suitable for outlets that serve large amounts of soft drinks quickly, such as a sports stadium or a busy fast-food restaurant.