stormy clot

This is one of the tests done to identify Clostridium perfringens. A litmus milk is used. Litmus milk is a light purple liquid aliquoted in a bijou bottle. Prior to us for THIS test, sterile rusty nails are put into it. Sterile so that it is not contaminated. Rusty nails so that an anaerobic atmosphere is created. Remember that Clostridium is an aerotolerant anaerobe, i.e. it will not die on exposure to oxygen.
Inoculate the litmus milk with the test organism. Incubate anaerobically at 37 degrees for 18-24 hours. You can use a candle jar.
After incubation, examine for the presence of a stormy clot. I will first describe how the stormy clot is formed, and then describe its appearance.
Lactose in the milk is fermented. Acid and gas are produced. This acid causes coagulation of the casein. Casein combines with the gas to produce the distinctive and characteristic stormy clot.
A stormy clot is the production of whitish cloud like coagulation at the top of the litmus milk. Below that is the paler litmus milk. It is almost like the clouds we see at dusk, large white cumulonimbus clouds above a very pretty pale blue sky.