Explain the Swab Method?

Swab method is the oldest and widely used method in food and dairy industry and was developed by W.A. Manheimer and T. Ybanez in 1917. A sterile cotton swab is used which is made up of wound cotton head on a 12-15 cm long wooden stick. It is moistened with a sterile rinse solution and used for rubbing the surface to be examined.

Swabbing is the most commonly used method to sample food contact surfaces. It is generally used for surfaces having high contaminant counts. Swab samples can be taken from any surface of the food processing facility like chillers, coolers, freezers, utensils, holding tanks, packaging machines, meat slicers, floor, walls, drains, working table, interior of a pipe or equipment piece etc. and analyzed by plating technique for total plate count. The exposed swab is kept back in the test tube containing a suitable diluent and kept in a refrigerator till used for plating. The organisms in the diluent are counted by SPC or any other method used for enumeration, as discussed earlier. Calcium alginate swabs can also be used in place of cotton swabs. Sterile 0.85% saline can be used to rinse the swab. It is used to hold microbial cell temporarily in stasis so that no change in number occur between the sampling and plating events.