The applicability of Emmerling's principle (“mould test”) in food microbiology

Summary

Emmerling's test, wherein feed is moistened and then stored at elevated temperatures and inspected for mould growth (“mould test”), has been adopted for the microbiological evaluation of cereal products, cocoa and spices in Regulations under The Netherlands Food Law. In spite of repeated criticism both in Germany and in The Netherlands, the procedure has hitherto been maintained because of its incontestable simplicity and because results are known within 24 hours.

It is shown that the test can in fact be used, in principle, for the mycological evaluation of products, which are heated in the course of their industrial preparation, such as cocoa and rolled oats and to a lesser extent also of other cereals and spices which do not contain antimicrobial substances. It is prerequisite here, however, that (i) simultaneous bacterial development is inhibited by the addition of chlortetracyclin or oxytetracyclin; (ii) the temperature of incubation is 20–25°C.; (iii) incubation is continued for at least three days.

It is demonstrated that the usefulness of a procedure of the type of theEmmerling mould test in the bacteriological examination of foods,i.e. a test wherein simultaneous development of moulds and yeasts is inhibited by the addition of the antibiotic pimaricin, seems very doubtful, save perhaps for presumptive laboratory control in factories preparing preheated dry foods, which are virtually sterile.

It is explained that a non-specific test of this sort should definitely not be considered for final Public Health control,e.g. of precooked cereal foods, but that the usual quantitative tests for pathogenic bacteria and for indicator organisms are imperative here.