Dan Crothers looks at how laboratory paddle blenders have offered fast reliable homogenisation for a wide range of laboratory samples.
Sample preparation is a critical step in all safety analyses. High quality sample preparation is vital to the ultimate delivery of good quality, accurate results and, therefore, should be a key consideration when analysing samples for safety purposes. Numerous industriesdepend on rapid and safe sample preparation techniques for production and quality monitoring in order to be able to intervene when required in active processes, while minimising downtime.
Be prepared
For example, food materials are inherently variable, therefore it is essential that this variability, both within and between samples, is minimised as greatly as possible prior to microbiological analyses with proper sampling and also sample pre-treatment techniques.
Following the use of appropriate statistical methods to obtain representative and replicate samples, the resulting sample then requires an efficient sample pre-treatment procedure to ultimately deliver rapid, reliable and reproducible analytical results within given limits and tolerances. To achieve this, material must be made less heterogeneous by reducing the particle weight and size within the primary sample. This enables smaller subsamples to be taken for a representative analysis of the whole and also ensure maximal organism recovery. Furthermore, if organisms are not released from the sample matrix via homogenisation, they will not grow or multiply in any subsequent culturing or selective isolation procedure. Consequently, another key issue to be addressed by a sample preparation method is the easy elimination of the potential for any cross-contamination between samples, thereby ensuring accurate results.
Finally, in addition to delivering a contaminant-free, reproducibly homogenised sample when reducing a food sample, the durability and reliability of the blender used must be considered. With increasingly stringent regulatory requirements being set within both research and production environments, such as for product monitoring and quality control, any laboratory analysis stoppages could ultimately delay final product release with subsequent cost implications.
A well mixed solution
Seward's Stomacher laboratory paddle blenders have offered fast reliable homogenisation for a wide range of laboratory samples. The Stomacher machines work by the action of twin reciprocating paddles on the sample contained inside a sterile plastic bag, ensuring effective and fully reproducible homogenisation of samples without cross-contamination between samples. The Stomacher has been proven in laboratories around the world to be a valuable tool in industry, research, education and healthcare. As previously discussed, this is because in scientific procedures the quality of the sample and its preparation are critical to accurate final results. Stomacher has been and continues to be developed to deliver this outcome.
The Stomacher 400 Circulator has been demonstrated to achieve enhanced recovery of microorganisms. The Stomacher 400 Circulator principle improves organism recovery over older square paddle blender designs by enhancing stirring and extrusion forces applied to the Stomacher Bag contents. This is achieved by the combination of curved paddles, a central island baffle and round bottomed Stomacher bag (Fig. 1).
In operation the paddles crush the sample but due to the patented curved shape of the Circulator paddles, they also simultaneously circulate the bag contents. This circulating action creates an enhanced washing effect on the sample debris as it is crushed. Consequently, more organisms are driven into suspension to ultimately provide a better homogenised sample for analysis.
Improved organism recovery
The patented curved paddle enhancement is a positive benefit to pathogen testing procedures in both traditional microbiology and PCR based techniques. In a study undertaken by an external food research laboratory to evaluate the Stomacher 400 Circulator in comparison to the original square paddle model, a variety of food types were assessed from dairy, meat, poultry, vegetable and confectionary.
Each food type was analysed 10 times for total viable count (TVC) and optical density using both new and old Stomacher models.
The results of the study suggest that the Circulator model breaks up food particles more efficiently and should, therefore, give a better recovery of microorganisms from some types of food, particularly those where microorganisms are embedded within the food matrix (eg cheese and chocolate). This would be a significant benefit for the recovery of pathogens, such as Salmonella, from such products.
'Stomaching' the future
Such has been the Stomacher's global success that now within the bioscience and healthcare markets the new developments of the Stomacher 80 Biomaster and micro80 are proving invaluable for safe and efficient diluent-free processing of biological tissue samples at volumes as low as 250µL.
Consequently, the Stomacher paddle blender continues to demonstrate its versatility for the efficient blending and homogenisation of samples in numerous types of laboratories worldwide.
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Dan Crothers is with Seward Ltd, Worthing, West Sussex, UK. www.seward.co.uk
