In the field of aseptic bottling technology, that aims at not using preservatives, the grade of acidity of the product is the main factor that influences the choice of technology to be used and the global complexity of the process. Generally, the product acidity is defined by the concentration of ionic hydrogen (H+) present in the solution. The grade of acidity of the substance is measured in pH, which is a scale based on the activity of the ionic hydrogen in watery solution. This is defined as follows:

pH = −log10H+

Generally almost all commercial soft drinks are acid. The entity of the acidity is however, very important since a major part of the bacteria develops better for values of pH near to neutrality, whereas when the pH diminishes their growth notably slows down. For this reason, in the case of aseptic bottling, two general subdivisions were created , that correspond in general to different production technology.

  • High Acid Beverage (HA), when the pH is lower than 4,6
  • Low Acid Beverage (LA) when the pH is higher than 4,6
     

 
The borderline represented by pH=4,6 has microbiological foundations since over said level of acidity it is not theoretically possible for bacteria to develop and there is only a possible growth of moulds or yeasts.

It is therefore clear as to how some of the most common drinks are suitable for high acid bottling whereas to bottle other drinks, such as those containing milk, it is necessary to use more complex systems dedicated to low acid products, where the reduction of initial contamination represents a higher factor of criticality.