Laboratory mixer, an essential instrument to obtain representative samples

Sampling for microbiological analysis purposes is challenging mainly for two factors: i) it should be carried out under sterile conditions and ii) the food, drug or cosmetic sample to be analyzed needs to be representative. To achieve both points and a good extraction of the possible pathogen to be detected is usually performed by applying mechanical forces and working with a laboratory mixer, because we can get a representative sample and, at the same time, prevent the development of possible microorganisms.

When the foodstuff or the material to analyze is not immediately dispersed in water the sample has to be shaken or homogenized it with a diluent in a bottle or bag. In this case, it is essential to have available a liquid sample which has a bacterial content that is representative of a solid, semi-solid, paste or powdery original material. The liquid originated is easy to cultivate or even to process microbiologically.

In this point, the importance of getting a representative sample is especially delicate to get a good microbiological control. Despite the emergence of novel molecular and high-throughput detection methods such as the PCR in food testing, the recovery, isolation, and enumeration of bacterial pathogens in food are still primarily based on culture techniques, the current gold standard in the field.

In fact, the mere presence of bacterial DNA or RNA, which are the main target of novel molecular methods, cannot predict the risk of infection. With the classical microbiological methods the formation of visible colonies requires the successful recovery of the target bacteria out of a food matrix in a viable and replication-competent state. Therefore, sample preparation is critical for the successful subsequent microbiological detection

The importance of getting a representative sample

 

One of the most important working areas for IUL Instruments is the food industry, which is why laboratory mixers work to simplify the microbiological testing and make possible the obtention of a homogenized sample that is representative of the whole food. 

In general, the homogenization process involves the original substance and the support liquid or diluent being brought into close contact to establish a balance in the microbiological content of both. The laboratory mixer starts when the sample is blended with the diluent inside a sterile bag by means of the application of forces to the outside of the bag by means of paddles, in this way, avoiding contact with the sample. The process facilitates the use of reusable material which must washed and sterilized so as not to invalidate consecutive samples.

Studies have indicated that with the specific dose of time this procedure can reach a good representative sample even with those samples that show inner-matrix contamination. For example, some pathogens are not necessary homogenously distributed throughout the entire matrix.  Little is known about the distribution of bacterias through the product or whether they are only present in the surface. For this reason, it is very important to acquire a representative sample to be analyzed.

Dilutor and laboratory mixer: a perfect match

 

As it has been said, having a representative sample is essential, but how we can get this sample? Standardizing the process from dilution to homogenization is the key. To do this, we take a sample amount of the food, dilute it with a quantity of liquid, which is what the Dilutor would do, and then we can blended it with the laboratory Mixer so in order to make accessible the bacterias to be cultivated.

On the one hand, the laboratory mixer is a simple and yet robust instrument designed to work for prolonged periods without maintenance, and in any kind of environment. Initially devised for the homogenization of different materials in order to take representative samples from them. It is currently used for other applications related to microbiological analysis as well.

The Masticator

 

IUL’s laboratory mixer, known as Masticator, carries out a profound homogenization which makes it possible to obtain a diluent liquid which is perfectly representative of the sample that has to be analyzed. It’s working principle lies in the use of bags made of strong polyethylene or other plastics, inside which the original sample and the diluent liquid are placed.

The Masticator acts upon the sample and the diluent through the sides of the bag, which, at this moment, is perfectly sealed, without either soiling or contaminating any part of it whatsoever. Furthermore, it works with the minimum amount of noise and without the necessity of cleaning between samples.

On the other hand, the Dilutor is a solution for laboratories in need of increasing their sample processing capacity and traceability in their gravimetric dilutions and dispensings. In this way, more precise and accurate robustness and results can be achieved.

Currently, the more developed Dilutor made by IUL Instruments is the Smart Dilutor W, launched to provide reliable solutions in the automation of quality control laboratories. The dilutors of IUL complement the laboratory mixer in order to speed up sample preparation before performing the corresponding microbiological control.

The sterility of samples

 

Another important topic is the sterility of the samples, other than making sure that the sample to homogenize is a representative of what we are going to analyze, it is just as essential as getting a sterilized sample.

To guarantee the sterility of the sample is important to work with the optimal quantity of sample to avoid contaminations and guarantee a good handling of the sample. That is why is fundamental to use 80 ml and 400 ml sterile bags and take only the certain amount of sample that is needed.  In fact, following microbiological workflow inoculation is possible to be carried out with only 50 ul of the sample per Petri dish.

Laboratory mixer and its differents applications

 

The laboratory mixer can be used in veterinary research or medical protocols, as well as in the extraction of residues from tissues for antibiotic methods. It can also be used for cultivation and cell biology due to its high viability for tissue cell suspensions and rapid adhesions to the cultivation bottle.

Another of its applications is in clinics and doctors: rapid treatment of enzyme-free expectorations for bacteriological, immunological and biochemical analysis and commissioning cellular biopsies.

In addition, laboratory mixers can also be useful in pharmaceuticals (sample treatments), agri-food laboratories (extraction of pesticides and medicines) and biochemistry (heavy metals), among many others.

In a nutshell, it becomes evident that the general lack of clear protocols regarding sample pretreatment might be responsible for considerable interlaboratory differences in pathogen detection and microbiological analyses. This is not only important for microbiological investigations, but might also be suitable as a general reference point for other whole-cell detection methods.

When choosing the appropriate homogenization device should consider not only the efficiency of detection, but also the ease of handling, costs and automation capabilities. Standardized and harmonized sample preparation protocols are needed for different food matrices, therefore IUL’s laboratory mixer and Dilutor are essential.