Low-Oxygen Bacteria
It should be noted that the vacuum packaging process does not eliminate all forms of bacteria. There are some types of bacteria that favor low-oxygen atmospheres, reproduce and exist quite happily in a vacuum packaged state. Because the bacteria that causes food to spoil has been nearly eliminated through the vacuum packaging process, the normal clues of spoilage (odor, color, taste, texture) may not be present. This creates a potentially dangerous, possibly deadly factor for botulism poisoning. This is why food that would otherwise spoil quickly, such as fresh meats, fruits and vegetables must be frozen in addition to being vacuum packaged.