Egg yolk paste for determining some food poisoning bacteria.

Egg yolk, aseptically prepared from fresh eggs, was partially dehydrated with a 40% high fructose corn syrup solution, and 10% salt was added. This salted yolk paste was added to mannitol salt agar for the detection of Staphylococcus aureus, to NaCl-glycine Kim and Goepfert medium for detection of Bacillus cereus, to Clostridium welchii agar for detection of C. perfringens, and to Gifu anaerobic medium for detection of C. botulinum. These food poisoning bacteria showed the same lecithovitellin (LV) reaction on these media as on the same media prepared with fresh egg yolk. The yolk paste could be stored at -20 C without freezing and did not show any bacterial growth after holding at 25 C for 30 days. The increased salt content resulted from the addition of salted yolk paste to the media did not inhibit the growth of the food poisoning bacteria used in these experiments. For the identification of the food poisoning bacteria used in this work, and which give a LV reaction, salted yolk paste is more convenient to use than yolk separated from fresh shell eggs.