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ObjectiveThe aim of this process is to dissolve a quantity of carbonic gas in to different products (for example, in to wine) to obtain a gasified (carbonated) final product. It is also used for still wines, under some conditions, to protect the aroma and the colour and to increase the tasting smell. When dissolved in water, carbon dioxide is sparingly soluble and thus, slowly released, forming bubbles that provide a characteristic mouthfeel and a unique taste when consumed. In addition to the organoleptic property, under suitable conditions, CO2 has a preserving property by the inhibition of the development of harmful aerobic micro-organisms. This however is not a substitute for other methods used to ensure microbiological safety.
Field of applicationCarbonation is an important process step in the preparation of many soft drinks and certain types of mineral waters. It is also applied in the wine industry.
Techniques, methods and equipmentCarbonation results from the impregnation of a liquid with carbon dioxide gas (CO2) to form carbonic acid. The CO2 was traditionally obtained from of lime kilns (by heating calcium carbonate) but this has now been universally replaced in the soft drinks sector by the storage of bulk liquefied gas externally delivered by a CO2 supplier. The gas is stored within pressurised insulated tanks kept at a very low temperature. In common practice, the gas tends to be generated as a by-product of fermentation or chemical processes from companies outside of the soft drink sub-sector.
The degree of carbonation varies for each soft drink formulation, from 4 g/l in fruit drinks to 9 g/l in mixer drinks and 12 g/l in soda water. The CO2 gas content is one of the smallest constituents by weight (7 g/l) but possibly the most important, in regards to palatability of the product. CO2 is one of the very few gases suitable for providing the effervescence in soft drinks. It is non-toxic, inert, and virtually tasteless and allows for convenient bulk transportation and storage.
CarbonatorsA carbonator combines carbon dioxide gas with the liquid to be carbonated. Current carbonators can be classified into two main categories: those that carbonate water only and those that carbonate the finished product mixture of syrup and water, these are sometimes coupled with coolers, often referred to as “carbo-coolers”. The principal designs available are carbonators with integral coolers, draining wall heat exchangers and carbon dioxide injectors.
In combination with this process, de-aeration, i.e. the removal of air, is vital and is usually applied to the water component in a preceding stage. The presence of air can create spoilage problems. CO2 is sometimes used to flush out air, however the use of mechanically de-aerated water has become more popular in recent years.