infectant concentrations, but in reality they only highlight conditions under which disinfectants that have failed should not be used.

Through the auspices of national standard organizations, many countries have standard disinfectant testing procedures, including Australia, New Zealand, South Africa, France, Germany, The Netherlands, the UK, and the United States (44). There is little standardization between countries, however, and to address this issue, with the planned harmonization of Europe in 1992, the European Suspension Test (EST) (45) was published with some agreement between European countries. To pass the EST, a disinfectant must reduce the viability of 5 test organisms by 5 log orders in 5 min at both low (0.03% bovine albumin) and high (1.0% bovine albumin) soil levels. Results for two examples each of a range of disinfectant types are shown in Table 6. These results illustrate a number of points including: the relative resistance of microbial species, the variation of disinfectant action within a single microbial species, the influence of organic load and hence the necessity to thoroughly clean prior to disinfection in practice, and the range of biocidal action between and within product types. In its early stages of development, a collaborative trial in 10 European countries found the EST to be sufficiently repeatable and reproducible to be adopted internationally (46).

Microorganisms are not primarily found in the food production environment in suspension. In an attempt to more closely simulate an in-use conditions surface, tests have been developed in which microorganisms are dried onto surfaces prior to disinfection (47-49). Although these tests provide a stronger challenge to the disinfectant (50), there are problems with the tests in that the drying process may alter microbial resistance, it is difficult to remove a consistent proportion of microorganisms for enumeration after disinfection and again, microorganisms are rarely dried onto surfaces in practice. A surface test has recently been described (51) in which disinfectants are tested against bacterial biofilms developed on stainless steel samples and in which the viability of the biofilm was assessed, while surface bound using a Malthus microbiological growth analyser (Malthus Instruments Ltd. (Radiometer), UK). The relative resistance of bacteria when attached to surfaces as compared to in suspension is shown in Table 7. A range of disinfectants was tested under the conditions of the EST at their manufacturers' recommended concentration (MRC) for bacteria in suspension and at the MRC and 10 and 100 times this concentration, when attached to a surface. The results showed that bacteria were 10 to 100 times more resistant to biocides when attached to a surface and that biocides that performed well in suspension did not necessarily perform well on surfaces. Care should therefore be exercised in transferring the results from suspension tests to in-use applications.

Fantastic Organic Food Facts

Fantastic Organic Food Facts

Get All The Support And Guidance You Need To Be A Success At Utilizing Organic Foods. This Book Is One Of The Most Valuable Resources In The World When It Comes To Getting The Right Information About Eating Healthy With Organic Food.

Get My Free Ebook

Post a comment