DIN SPEC 10534: 2019-02. Food hygiene - Commercial dishwashing - Hygiene requirements and testing. 

(The Standard DIN SPEC 10534 have been deleted and replaced by EN 17735: 2022)

Test not accredited in our laboratory.

The standard DIN SPEC 10534 specifies the hygiene requirements related to the design, construction and operation of commercial dishwashing equipment used for cleaning wash ware that is used in contact with food, such as, crokery, glassware, cutlery, reusable boxes and similar items, used in kitchens, such as restaurants, canteens and hospitals, and in commercial companies as bakeries, butchers, etc. Household dishwashing equipment and sanitizing machines used to treat medical devices are excluded from the scope of this standard.

The standard DIN SPEC 10534 provides information on the requirements for commercial dishwashing equipment and describes methods for testing the hygienic performance of dishwashing equipment. The requirements to test the hygienic performance of a washing process are: a) The wash ware must be visually clean; b) The wash ware must be dry upon removal from the wash ware carriers, tolerating the remaining drops on the support points and the residual humidity inside the hollow items; c) The machine must achieve a level of disinfection performance in accordance with microbiological requirements.

Depending on the scope of application and the intended use there are different tests to evaluate the hygienic performance of a washing process. In our laboratory, only type tests are performed, the tests that must be carried out by manufacturers to verify that the dishwasher works in a hygienic way. For this, the client must send the dishwasher equipment to our laboratory and the test would be carried out with the detergent described by the standard. The different types of tests indicated by the standard are described below.

1.-The type tests, which aim is to check the cleanliness and dryness by means of a visual inspection, to carry out the temperature control of the equipment and to analyze the reduction obtained after the process in the Enterococcus faecium bacteria on the test supports. The standard indicates that the type test can be carried out with different bioindicators (test objects contaminated with interfering substance and inoculated with the test bacteria), suitable for the main use of the dishwasher.

Thus, the test used to test the performance of commercial warewashers used mainly as dishwashing machines, to clean and disinfect crockery and cutlery, includes the evaluation of the cleaning and disinfection performance with stainless steel bioindicators contaminated with a specific inoculum of Enterococcus faecium in a medium of bovine albumin soil, mucin and starch, which are placed in 24 cm diameter plates or cutlery trays. To perform the assay with the bioindicators on the dishes, the rack for the dishes is completely filled according to the manufacturer's instructions and the bioindicators are fixed to the dishes using supports (one bioindicator per dish will be used). The number of dishes will depend on the load of the test dishwasher. To test with the bioindicators on the cutlery trays, load the cutlery tray of the commercial test dishwasher with three spoons, three forks and three knives in each compartment and placing a bioindicator between the cutlery in each container. 8 stainless steel bioindicators should be tested per cycle. The test is carried out using the shortest cycle program and using a reference detergent and rinse aid indicated by the standard. At the end of the cycle, new test bioindicators are placed up to 3 test cycles. Prior to microbiological examination of bioindicators, they should be visually inspected for cleanliness. The degree of dryness of the dishes and cutlery should also be recorded. In the plate test, 90% of the bioindicators should show a ≥ 5 log reduction and 10% should show at least a ≥ 4 log reduction in E. faecium titre. In the cutlery tray, 7 out of 8 bioindicators should show a ≥ 5 log reduction and 1 in 8 should show at least a ≥ 4 log reduction in E. faecium titre. If the test requirements are met, it can be concluded that other laundry items will also be cleaned and disinfected if properly placed.

For commercial warewashers that are used primarily as glasswashing machines, the type test is performed using special bioindicators (beakers or wine-tasting glasses contaminated with E. faecium in reconstituted skimmed milk soil medium). To carry out the test, the glass tray of the test equipment is completely filled following the instructions for use and the reference liquid detergent at 3 g/L and the reference rinse aid indicated by the standard are used. The number of bioindicators will depend on the load of the equipment. The test should be done using the shortest program cycle. Once Before microbiological evaluation, glassware used should be visually inspected for cleanliness and degree of dryness. 90% of the bioindicators should show a reduction of ≥ 5 log and 10% should show at least a reduction of ≥ 4 log in the E. faecium titre.

The type test for commercial warewashers that are mainly used for cleaning re-usable boxes or containers, used for the storage and transport of non-packaged food in the commercial environment, is carried out using bioindicators of stainless steel contaminated with a certain inoculum of E. faecium in a soil containing bovine albumin, mucin and cornstarch, which adhere to reusable boxes or containers. At least eight reusable boxes or containers with five bioindicators each will be tested. A reusable dummy box or container, equipped with supports, can be used in the type test. This box / container is used seven more times with the newly added indicators. The machine should be loaded according to the instructions for use, use the reference detergent and rinse aid, and test using the shortest program cycle. Prior to microbiological evaluation, bioindicators should be visually inspected for cleanliness. In addition, the degree of dryness of the reusable boxes or containers will be recorded. To demonstrate the hygienic performance of the washing process, 90% of the bioindicators should show a ≥ 5 log reduction and 10% should show at least a ≥ 4 log reduction in E. faecium titre.

2.-Post-installation tests are organized by the operating company and are intended to verify that commercial dishwashers meet hygiene requirements, if they are operated in accordance with the instructions, under their actual conditions of use. The tests should be carried out during the main operating period. At least after the dishwasher has been running at full load for at least 0.5 hours or after at least three wash cycles. If the dishwashers have not previously been type tested, the post-installation tests must include at least the following microbiological tests: total aerobic count of the surface of the washing dishes, determination of the total aerobic count in the detergent solution and tests with bioindicators similar to those described in the type test, but with the detergents used in real conditions. These microbiological tests should also be carried out after installation in the case of commercial dishwashers with special hygiene requirements, for example in hospitals. Furthermore, whether the type test has been carried out or not, the post-installation tests will always analyze the cleanliness and dryness of the washed items; the temperatures; the dose/concentration of treatment agents; and the quality of the water.

3.-The daily inspection refers to the control of the relevant parameters for hygiene by the operating company.

4.-The periodic inspection will be carried out every six months and additionally if there is any suspicion that a machine is not working satisfactorily. It is intended to identify more serious hygiene failures.

Of these tests in IVAMI, only the TYPE TESTS (#1.-) could be carried out, including the elimination of Enterococcus faecium, since the rest of the tests must be done after the installation of the equipment in its place of use.

Simulated-use test for PT4 products intended for disinfection in dishwashing machines

(DIN SPEC 10534:2019-02 standard and BPR Guidance) 

The DIN SPEC 10534 standard describes a test to evaluate commercial warewashes equipment, using a reference detergent. Nevertheless, the BPR Guidance states that for testing a PT4 product intended for disinfection in a dishwashing machine, the procedure described in the DIN SPEC 10534 Standard might be helpful for designing a simulated-use test. In our laboratory, we perform a simulated-use test based on the DIN SPEC 10534 Standard to evaluate the efficacy of PT4 disinfectants used in dishwashing machines, using a domestic dishwasher.

The BPR guidance indicates that for tests with PT4 products (for disinfection in the food area) intended for disinfection in dishwashing equipment, the following tests are required for these disinfectants:

-        A quantitative suspension test (phase 2, step 1); and

-        A quantitative surface test (phase 2, step 2); and

-        A simulated use or field test (phase 3) for disinfectants used in (dish) washing machines;

All tests must simulate practical conditions appropriate to their intended use (temperature, dirt, different surfaces, contact time, etc.). The BPR guide indicates that dishwashing products are normally used at 40ºC and that therefore tests should be carried out at this temperature. If they are used at lower temperatures, for example if they are used in the rinse step after washing, the tests can be carried out at 20°C.

The laboratory tests should be performed under these conditions. If the exact conditions cannot be met, for example, in household machines, reasonable worst-case conditions must be tested (e.g. lowest temperature, shortest time…).

According to the BPR Guidance, equipment and dish washing disinfectants should be at least sufficiently effective against bacteria and yeasts. Nevertheless, for uses in industrial dish washers for specific purposes, an exception can be made when sound justification is provided. For all other groups of organisms, data only have to be provided when activity against those organisms is claimed. Relevant groups of test organisms, next to bacteria and yeasts, can be fungi (fungal spores), viruses, bacteriophages, and bacterial spores. Bacteriophages are mainly of importance in the dairy industry.

The test organisms used in efficacy tests are normally stated in the applicable standard test methods. For dish washing disinfectants Salmonella spp., Listeria spp. and Campylobacter jejuni are relevant target organisms. For products which claim general efficacy against bacteria, the standard test bacteria should be tested. For these products, efficacy against Salmonella spp., Listeria spp. and Campylobacter jejuni is assumed, because they are more susceptible than the standard test bacteria. When the product is intended to be used at high temperatures (>40 ºC) relevant test organisms for these temperatures should be used (Enterococcus faecium, for bacteria).

In general, dish washing disinfectants should be tested under dirty conditions since these products are mainly used for combined cleaning and disinfection. Tests under clean conditions will only suffice when the label instructions state that cleaning prior to disinfection is necessary or when this is incorporated in a previous cycle of the (dish)washing machine. If this is not stated on the label the test should be done under dirty conditions. Tests should be carried out with soiling for clean or dirty conditions in accordance with the test requirements. The DIN SPEC 10534 standard states an interference substance of bovine albumin, mucin and starch for stainless steel bioindicators, and reconstituted skimmed milk for glasses. The BPR Guidance states as interference substance for general disinfection in food industry 3g/l of bovine albumin for dirty conditions and 0.3 g/L of bovine albumin for clean conditions; for milk industry 10g/L of skimmed milk and for the meat industry 3g/L of bovine albumin + 3ml/L of sheep erythrocytes.