De­vel­op­ment of a bio­cat­alyt­ic color in­di­ca­tor sys­tem for pro­cess con­trol of dis­in­fec­tion in com­mer­cial dish­wash­ers

IGF 17664 N

The re­quire­ments for hy­giene in the food sec­tor arise from the EU reg­u­la­tion on the hy­giene of food­stuffs i.e. (EC) 852-854/2004, which re­quire a hy­giene man­age­ment sys­tem based on the HACCP con­cept (Haz­ard Anal­y­sis Crit­i­cal Con­trol Point) for can­teen kitchens and many other areas.

Dish­wash­er pro­cess­es are rec­og­nized as im­por­tant Crit­i­cal Con­trol Points with­in these hy­giene man­age­ment con­cepts and must be con­trolled pe­ri­od­i­cal­ly, for which the op­er­a­tor has to take care.

How­ev­er, end prod­uct and in-pro­cess con­trols de­scribed in re­spec­tive stan­dards (e.g. DIN SPEC 10534) ex­hib­it major dis­ad­van­tages. These dis­ad­van­tages re­sult from the use of con­ven­tion­al mi­cro­bi­o­log­i­cal cul­ture meth­ods pro­vid­ing re­sults only after sev­er­al days. This test­ing is ex­pen­sive and re­quires a mi­cro­bi­ol­o­gist and a lab. A sim­ple and quick method for rou­tine con­trol is not avail­able.

In the course of the pro­ject a new rapid assay sys­tem for the pro­cess con­trol of dish­wash­er pro­cess­es was de­vel­oped, where­in the spe­cif­ic ac­tiv­i­ty of en­zymes is dis­played by dye sys­tems. Since ger­mi­ci­dal pro­cess­es are based pre­dom­i­nant­ly on pro­tein de­na­tur­ing ef­fects, germ killing can be rep­re­sent­ed by the de­nat­u­ra­tion of en­zymes.

Func­tion­al sam­ples of the de­vel­oped en­zy­mat­ic pro­cess chal­lenge de­vices con­sist­ed of porous ce­ram­ics with a height of 1.2 cm and a cir­cum­fer­ence of 4.5 cm. Load­ed with en­zymes they demon­strat­ed a good agree­ment with in-pro­cess con­trols based on mi­cro­bial in­ac­ti­va­tion, both in the lab­o­ra­to­ry and in prac­tice (ex­em­plary ap­pli­ca­tion at 6 mass cater­ing fa­cil­i­ties). With­in about 10 min­utes the de­vel­oped sys­tem al­lowed the eval­u­a­tion of dis­in­fec­tion per­for­mance of dish­wash­ing pro­cess­es by vi­su­al anal­y­sis of coloured re­ac­tion prod­ucts re­leased from chro­mogenic sub­strates.

The rapid test is in­ex­pen­sive and does nei­ther re­quire skilled mi­cro­bi­ol­o­gists nor a lab­o­ra­to­ry. The hy­gien­ic safe­ty in dish­ware dis­in­fec­tion will be in­creased by using this rapid test sys­tem, which eas­i­ly en­ables fre­quent in-pro­cess con­trols.

The research report is available on request from FRT.

The IGF-pro­ject IGF 17664 N of the re­search as­so­ci­a­tion Europäische Forschungs­ge­mein­schaft Reini­gungs- und Hy­gien­etech­nolo­gie e.V., Cam­pus Ficht­en­hain 11, 47807 Krefeld, was sup­port­ed with­in the fund­ing pro­gram „In­dus­trielle Gemein­schafts­forschung und -en­twick­lung (IGF)“ by the Fed­er­al Min­istry of Eco­nom­ic Af­fairs and Cli­mate Ac­tion due to a de­ci­sion of the Ger­man Par­lia­ment.