Conventional and rapid analytical microbiology R. P. Betts, Campden and Chorleywood Food Research Association 8.1 Introduction The detection and enumeration of microorganisms either in foods or on food contact surfaces forms an integral part of any quality control or quality assurance plan. Microbiological tests done on foods can be divided into two types:(a) quantitative or enumerative, in which a group of microorganisms in the sample are counted and the result is expressed as the number of the organisms present per unit weight of sample; or(b) qualitative or presence/absence, in which the requirement is simply to detect whether a particular organism is present or absent in a known weight of sample The basis of methods used for the testing of microorganisms in foods is very well established, and relies on the incorporation of a food sample into a nutrient medium in which microorganisms can replicate thus resulting in a visual indication of growth. Such methods are simple, adaptable, convenient and generally inexpensive. However, they have two drawbacks: firstly, the tests rely on the growth of organisms in media, which can take many days and result in a long test elapse time; and secondly, the methods are manually oriented and are thus labour intensive Over recent years, there has been considerable research into rapid and automated microbiological methods the aim of this work has been to reduce the st elapse time by using methods other than growth to detect and/or count microorganisms and to decrease the level of manual input into tests by automating methods as much as possible. These rapid and automated methods have gained some acceptance within the food industry and could form an important quality control tool in the chilled foods area. Positive release of chilled foods on the results of a rapid method could increase the shelf-life of a8.1 Introduction The detection and enumeration of microorganisms either in foods or on food contact surfaces forms an integral part of any quality control or quality assurance plan. Microbiological tests done on foods can be divided into two types: (a) quantitative or enumerative, in which a group of microorganisms in the sample are counted and the result is expressed as the number of the organisms present per unit weight of sample; or (b) qualitative or presence/absence, in which the requirement is simply to detect whether a particular organism is present or absent in a known weight of sample. The basis of methods used for the testing of microorganisms in foods is very well established, and relies on the incorporation of a food sample into a nutrient medium in which microorganisms can replicate thus resulting in a visual indication of growth. Such methods are simple, adaptable, convenient and generally inexpensive. However, they have two drawbacks: firstly, the tests rely on the growth of organisms in media, which can take many days and result in a long test elapse time; and secondly, the methods are manually oriented and are thus labour intensive. Over recent years, there has been considerable research into rapid and automated microbiological methods. The aim of this work has been to reduce the test elapse time by using methods other than growth to detect and/or count microorganisms and to decrease the level of manual input into tests by automating methods as much as possible. These rapid and automated methods have gained some acceptance within the food industry and could form an important quality control tool in the chilled foods area. Positive release of chilled foods on the results of a rapid method could increase the shelf-life of a 8 Conventional and rapid analytical microbiology R. P. Betts, Campden and Chorleywood Food Research Association