Spray Shadow Test

Retention Test

To control/review the efficiency of an installed interior cleaning system such as a beverage filler “just-in-time” visually, therefore a spray shadow test-or the retention test is performed. For classical bottling plants the area of filler and capper, for the aseptic filling plant outflow of the rinser to outlet belt are relevant for the hygienic status. Occasionally also whey and yogurt is applied; here however is likewise the problem of a nutrient entry and thus a potential risk of an accelerated or induced growth of microorganisms in non-functioning cleaning systems. The test medium therefore is an alcoholic solution of a special cellulose compound and an azo dye which cannot be utilized by beverage spoiling microorganisms.

The accomplished investigations demonstrate the microbiological immunity of this newly developed solution. In addition the advantage is in the high surface liability despite easily rinsing off the process fluid at the outer CIP and SIP, whether adhesive foam, adhesive gel or CIP media is used. The viscosity is higher or in the range of the usual beverages. The depth of colour is deliberately set relatively high in order to define the interpretation of spray shadows and “bleeding“.

In order to send this retentiontest-medium (RET-medium) without transport limitations (hazardous materials), a concentrate, i.e. without the addition of alcohol was developed. The concentrate is transported in a 5.0 litre container and must be filled then locally with commercial methylated spirit or alternatively isopropyl alcohol up to the mark and then to be shaken for about 1 minute to mix it properly. Thus this newly developed retention test medium can be used without any problems around the world, as the concentrate not has to be transported as a hazardous material.

RET-medium concentrate                  type K (3,28 litre) – Article-No.: 16.302.7001

The finished test-solution is usually applied with a high pressure spraying device (e.g.Mesto High pressure spraying device 3595F), constant application pressure minimum 2,5 bar (36,3 psi), on the machine surfaces and left to dry up for about 10-20 minutes. Then the check-up of cleaning and disinfection can be done by starting the appropriate cleaning and disinfection programs. The same applies in the same sense to check for installed jetting nozzles for the removal of product residues in conventional bottling plants for beer and beer-mixed drinks. To avoid misinterpretations, the re-sanitation programs should be carried out twice, so that the statement about the potential spray shadows and the lack of cleaning efficiency is clear.

Step 1: Cleaning of the machine surfaces

Step 2: Application of the RET-medium
Step 3: Drying the RET-medium
Step 4: Start CIP and SIP of the exterior rehygienization
Step 5: Visual inspection of spray shadows
Step 6: Visual check of „bleeding“ (Hygienic Design) with swabs

The examination for spray shadows is made visually as well as partially with swabs and can be documented photographically. Running down of the test medium, the so called “bleeding” out of gaps, pleats and machine components suggests an indication for a non-hygienic design (QHD) and the necessary dismantling for manual cleaning. Rough Surface structures can also be recognized as well as not suitable sealants or plastic structures according to DIN EN ISO 14159-2008 Safety of Machinery – Hygiene requirements for the Design of machinery, the DIN EN 1672-2 Food Processing Machinery – Part 2 Hygiene requirements, der EHEDG DOC 08 D-2004 Hygigenic Equipment Design Criteria as well as VDI-Guideline 4066 Sheet&xnbsp;1 Not appropriate Sealing Materials respectively plastic constructions.

Furthermore the structure of the cleaning program, the foam and thin film-stability as well as the intensity of injection pressures is evaluated. Also a proper rinsing of machine surfaces and components has to be ensured. Latter efficiency is examined by means of pH test strips.

The retention test should be integrated into the monitoring surveillance operation in order to carry out at regular intervals, respectively twice a year, a revision of the installed nozzle system for exterior cleaning and/or disinfection.

Further operational areas of the RET-medium are the examination of containers and tanks regarding the cleaning efficiency and spray shadows in the interior.

From 2014, April 1st the sales and marketing of the RET-Medium occurs about the company:


GIR – The German Institute of Rehygienization GmbH
Suedstr. 38, D-31867 Lauenau
Tel.: +495043-962586, Fax: +495043-962589
E-Mail: ret-m (at) institute-gir.com