AS 4659.1:2015 pdf download.Guide to determining the equivalence of food microbiology test methods Part 1: Qualitative tests.
4 PROCEDURE
4.1 Define the equivalence determination
The equivalence determination should be defined in terms of the following:
The target organism’s genus, species, serotype, etc.
The matrix under examination; the food and the characteristics that define it, e.g. the matrix should be defined in terms of characteristics such as pH, solids level, water activity, presence and composition of preservatives, season of production, brand name, etc. depending upon the nature of the matrix.
The procedures outlined in the Standard should be repeated for each matrix intended for use with the alternate method.
NOTE: When determining equivalence of an alternate method the laboratory should select the matrices to be included in the evaluation from those within the scope of the standard method. This Standard is not intended for the validation of matrices outside of the scope of either the alternate method or the standard method. Reference should be made to standard texts and the literature to support the choices of matrices. The choice should take into account the range of samples tested by the laboratory and the effects that the natural variation in significant parameters may have on the detection of the target organism.
(c) The alternate method—precisely defined by reference to a publication, manufacturer’s instructions and any optional procedures employed, or deviation from, the published method.
(d) The reference method—including the specification of any optional steps.
NOTE: For example, the validation of the use of XYZ agar as an alternative to Palcarn agar in the AS 50 13.24.1 method for the detection of Lisieria monocytogenes, from sauces containing pepper and a p11 greater than 4.5.
4.2 Define the conditions of the equivalence determination
The conditions of the equivalence determination should be defined in terms of the following:
(a) The laboratory where testing is performed.
(b) Controls observed by the laboratory during testing, for example, controls on the environment of the laboratory, prevention of cross examination, controls on media and reagents, calibration of equipment, etc. where these factors are considered critical to the success of either method.
(c) The staff performing the tests (experience, qualification and the like).
(d) The starting and finishing dates of the tests.
(e) The batch numbers of media, reagents, etc. used.
NOTE: This information is defined for the purpose of reporting on the equivalence determination and recording factors which may have some bearing on the results obtained. These factors do not necessarily affect the veracity of the study.
4.3 Select test organisms
At least five strains of the target organism should be selected. The reference culture prescribed in the Australian Standard method as a positive control should be one of the five strains. The other strains may be selected from the following list (in order of preference):
(a) Strains of the target organism isolated by the laboratory from previous samples of the matrix under examination.
(b) Strains of the target organism isolated by reference laboratories or industry sources as representative of the strains found in the type of matrix under examination.
(c) Strains of the target organism held by culture collections.
The strains selected should encompass the variation that may be expected to be found within the target organism in the matrix under examination.
The identity of the strains chosen should be determined by appropriate means (e.g., biochemical, physiological, serological or molecular) before performing further work. Consultation with a reference laboratory or an expert may be necessary. The source and identity of the strains should be recorded.
N()TE: it is possible, by the selection of test strains, to bias the results of the study. Care should be taken to select representative strains that do not possess characteristics that are likely to lead to a biased result being obtained.
4.4 Select samples of the matrix
Five typical samples of the matrix should be selected. They should represent as far as possible the range of variation found within the defined matrix. The choice of samples will depend upon the matrix, but may consist of samples from batches with high or low background contamination, or samples with different p1-I values, fat, protein or moisture levels. The aim of the selection is to choose samples which will represent the range of variation expected to be found in the defined matrix.AS 4659.1 pdf download.