About the testing procedure of DOX


What is a culture medium?

It is a nutritive substance in which cultures of bacteria are grown.

 

Are cell cartridges used to estimate total viable cells and coliforms the same?

No.  Different types of cell cartridge are used to analyze total viable cells and coliforms.  For Staphylococcus aureus and salmonella, cell cartridge for coliforms will be used.

 

Can cell cartridge for coliforms be used to evaluate Escherichia coli?

Cell cartridge for coliforms can be used to indicate whether or not Escherichia coli is present in a food product (qualitative test).  If the cell cartridge produces fluorescence under ultraviolet light at the end of DOX measurement, Escherichia coli is present in that food product.

 

How should culture medium and cell cartridges be stored?

セCell cartridges can be stored at room temperature.  Culture medium should be refrigerated at a temperature below 10 degrees celsius.

 

Our criterion value for abnormalities is set at 10^5 total viable cells per gram.  How long will it take to complete the analysis?

5 to 6 hours on average depending on how the food is processed.

 

How long will it take to confirm that there are no coliforms in a food product?

18 hours on average depending on how the food is processed.

 

Is it necessary to evaluate both total viable cells and coliforms?

As the purpose of the test for total viable cells and coliforms are different, it is left for each company to decide which type(s) of bacteria should be evaluated.  Total viable cells serve as an indicator of a good hygiene of the whole food handling process, whereas coliforms indicate if heated foods are adequately cooked or they are not cross-contaminated after cooking.

 

What is a “smear method”?

It is a testing method that evaluates the contamination of floors or walls of production sites, surface of manufacturing machines or palms and fingertips of the workers.  The method is to wipe certain surface area with a cotton-tipped stick dipped in diluent.  And after being incubated, the number of bacteria present on the stick can be observed.

 

Can DOX conduct the smear method?

DOX can conduct the smear method with 1ml of test solution.  The solution can be prepared using a commercial smear test kit.

 

What is a “stomacher”?

It is a machine that crushes and stirs foods.  Foods need to be finely crushed and mixed with diluent using a stomacher in order to count internally-lurking microorganisms.


How should cell cartridges and liquid mediums be disposed of?

Liquid mediums left unused should be discarded in the same manner as foods.  Their bottles are classified as plastic wastes.  Used cell cartridges should be sterilized and then disposed of according to the rules of each community.


Can a cell cartridge be inserted into any channel of DOX?

Yes.  Each channel operates independently, so you can insert a cell cartridge into any channel at any time.


Can a cell cartridge be used repeatedly?

No. It is non-reusable.

 

What is a “calibration curve”?

It is a graph that represents the bacterial count calculated using the time measured during the change in electric charge.


Why are there a variety of calibration curves? 

Different kinds of foods (e.g. meats, fishes and vegetables) have different kinds of bacteria.  Also, state of the bacteria changes according to how the food is processed.  Different kinds or states of bacteria have different speeds of multiplication.  Calibration curves show multiplication speed and initial number of bacteria.  Therefore, most suitable curve should be adopted according to the conditions mentioned above.


Would pH influence the testing?

 DOX cannot evaluate strongly-acidic food (pH3 or lower) because bacteria would not grow in such food.