Bacterial Flora of Ground Beef and Soy Extended Ground Beef During Storage

Ground beef and ground beef extended with 20% textured soy protein (TSP) were examined to determine the predominant bacterial flora present during storage at 4°C for 6 days. Bacterial numbers in the extended ground beef increased with time and at a faster rate than the nonextended product. Spoilage odors were also detected earlier in the TSP containing ground beef. For both extended and nonextended ground beef, Pseudomonas species were the predominant bacteria of fresh and stored samples. By the sixth day of storage at 4°C, the only psychrotrophs recovered were species of Pseudomonas. Considering these similarities, it appears that differences in the spoilage rate of extended and nonextended ground beef cannot be attributed to differences in the composition of their respective bacterial flora.