Preparation of sterile sponges for sampling red meat carcasses

Original drafts of these notes specified that sponges with an area of 100cm² were required for red meat carcass sampling.  In response to requests made by the meat industry and, in keeping with the Agency's aims of having regulations that are sensible, appropriate and practical, sponge sizes have been revisited.  Sponges with an area of at least 50cm² are now allowed.  In part, acceptance of the smaller size was the result of practical studies undertaken by the Agency and also, a consequence of the fact that smaller-sized sponges can be purchased directly from a number of commercial suppliers.

Most contract laboratories will supply their customers with the consumables that they require for sampling.  However, if your laboratory has difficulty in supplying/sourcing the sampling swabs, we have included below some information on commercial sponge suppliers. 

Please note that the FSA do not approve or endorse any of these products.  The Agency only lists the specifications that products are required to meet to be fit for their intended purpose.   The list above shows some products that are appropriate for the sampling of red meat carcasses.  Please also note that the list is not comprehensive, and that other suppliers may have products that are equally-well suited.  Suppliers who believe they have products that are suitable and would like to be listed should contact Mary.Howell@foodstandards.gsi.gov.uk and include their product specifications in the message. 

It is also acceptable to use “waffled” sponge dishcloths made from cellulose available from a supermarket for carcass sampling.  Examples of packages (not an exhaustive list) that are appropriate for use are shown in the photograph below.

Photograph 1: Packs of waffled sponges suitable for use for red meat carcass sampling

Other brands of cellulose dishcloths that are not shown in photograph 1 may also be appropriate for sampling red meat carcasses.  Irrespective of the brand of cellulose sponge that is used, it is important that the sponge does not contain additives designed to suppress the growth of microorganisms.  Do not use sponges that are described as "Germicidal", "Antibacterial", "Antimicrobial".  Furthermore, before use, all sponges need to be soaked in mains water for several hours and finally rinsed under running tap water to remove excess polymer and the chemicals used in the manufacture of the sponge.  A detailed protocol for the preparation of sponges is provided below.

Preparation of cellulose sponge dishcloths

Open the package and using a sharp pair of scissors, cut the sponges to an appropriate size (10cm x 10cm).  The Agency recommends using a sponge of at least 50cm² surface area before it is folded.  It is difficult to apply uniform pressure across the entire width of the sponge if it is too wide.  For this reason, the width of the folded sponge that will be in contact with the carcase should be no larger than 10cm. 

Half-fill a sink or large bucket with cold tap water and allow the cloths to soak for at least 2 hours.  Periodically, the sponges should be agitated or ideally squeezed out to ensure that polymer and chemicals used in the manufacturing process are completely removed.

After soaking, rinse each dishcloth individually under a running cold water tap to remove any residual chemical.

Stack the sponges in bundles of approximately 20 and package them in steam-permeable paper autoclave bags as shown in the photograph below.

Photograph 2: Pre-sterilised packs of waffled sponges

Sterilise the sponges by autoclaving at 121^oC for 20 minutes.

After sterilisation, sponges can be completely dried in a hot air oven set at 60^oC. Sponges dried in this manner remain sterile for up to 4 months when stored in a dry place at room temperature.

Alternatively, individual sponges can be aseptically transferred to stomacher bags and 10ml of sterile diluent added to re-hydrate the sponges.  Re-hydrated sponges can be frozen for up to 1 year without compromising their sterility.  Frozen sponges should be properly defrosted before use by thawing for 2 hours at room temperature.