Is it safe to drink milk after it is expired?

Many microorganisms can ferment milk. In most cases lactobacilli. There are two classes of lactobacilli. Those that form gas (CO2) and those that do not. Both produce acid (lactic acid) from sugar fermentation. They can do this in the absence of oxygen. One bacteria which can survive milk pasteurization is Bacillus cereus, a cause of food poisoning. This bacterium can cause vomiting and diarrhea due to toxins which it produces. B. cereus causes two types of food borne illness. One type is characterized by nausea and vomiting and abdominal cramps and has an incubation period of 1 to 6 hours. This is the short-incubation form of the disease. The second type is primarily abdominal cramps and diarrhea following an incubation period of 8 to 16 hours, the long-incubation form of the disease In either type, the illness usually lasts less than 24 hours after onset. In a few patients symptoms may last longer.