Preparation of Samples for Aflatoxin Testing

Aflatoxins are produced by various types of moulds which can grow on foodstuffs such as pistachio nuts, peanuts, cereals, dried fruits, etc. Much of the information in this report can also be applied to testing for other mycotoxins and ochratoxins. 

Permitted levels of these toxins are very low - typically 5 ppb or less. Analysis is carried out to ensure these limits are not exceeded, and the sampling and test procedure is controlled by legislation in many countries. However, the preparation for testing is not presently covered by any standardized method. For example, European guidelines state, “Finely grind and mix thoroughly each laboratory sample using a process which has been demonstrated to achieve complete homogenization.”*

Experimentation by a number of authorities has identified that preparation of samples by slurrying offers significant advantages over dry milling. Silverson high shear mixers have been used for this research, and it has been found that the aflatoxin content of repeated samples prepared by slurrying was more consistent than those prepared by dry milling. Silverson mixers are now used as the standard method in several countries. 

 

 

The Process

As mentioned above, in the absence of standardized procedure, there are many variations in the efficiency of the preparation (or extraction) process, according to the method and type of equipment used.

The volumes used for sample preparation will also vary according to the product being tested. 65 - 90 lbs samples are not uncommon. 

A typical procedure would be as follows: