Under optimum conditions, micro-organisms can grow very quickly and can ruin a food product within 24 hours. A stable, low temperature in chilled products is therefore essential for the success of MAP. By combining chilling, MA and extra inhibiting factors, an increasing degree of stress for bacteria is introduced until they no longer present any danger during the shelf life of the product. The most commonly used preserving factors in food production are chilling, water activity (aw), acidification (pH), redox potential (Eh) and individual preserving agents. Some of these are still at the trial stage in connection with MAP, while others are in regular use.
The principle of combined inhibiting factors is well documented and is often referred to as combination technology or hurdle technology. In addition to traditional preserving methods, a number of new methods have been tested with MAP. This is a knowledge based system in which the number and types of inhibiting factors are chosen to achieve the desired effect. Some have been incorporated into simulation models for microbial growth and preservation for specific types of illness-causing bacteria.