Effect of Lactic Acid Treatment on E. coli and Coliform Growth in Ground Beef after Different Storage Periods and Retail Display Days

ObjectivesThe study evaluated the changes in of Escherichia coli and coliforms counts in ground beef prepared from beef trimmings stored either 24 or 48 h after treatment with a 2–3% lactic acid dip (LA) for 3 storage periods of 7, 14, or 21 d after grinding. Materials and MethodsTwo sets of beef trimmings were dipped with 2 to 3% LA and stored for either 24 or 48 h prior to grinding. Additionally, 2 untreated sets were included as controls (CON), and were not treated with LA. Samples from each of the 4 sets of trim (n = 84; 4.54 kg) were ground, vacuum packaged, and further stored and sampled at 7, 14, or 21 d. After storage period was over, samples were re-ground using a 3.175 mm disk and a 25-g sample was collected to represent retail d 0. Three 454 g portions of each sample were placed on a polystyrene tray overwrapped with low-barrier polyvinylchloride film to represent retail d 1, 2, and 3. Packages were displayed in a coffin-style retail case maintained at 2 to 3°C. Packages were respectively sampled every 24 h according to its designated retail display day. A 25-g sample was collected, placed into a filter bag, and 225 mL of buffered peptone water (BPW) was aseptically added. The bag was stomached for 2 min at 230 RPM. Serial dilutions were made from meat rinse in 9 mL tubes of BPW. One mL from the bag or appropriate tube was plated to each EC petrifilm in duplicate. Both coliforms and E. coli petrifilm plates were incubated at 36°C ± 1°C. Counts were made at 24 h for coliforms and 48 h for E. coli. Counts and duplicate plates were averaged and converted to log CFU/g of ground beef prior to statistical analysis. Data were analyzed using statistical procedures of a 2-way ANOVA. A split-plot design was used with a whole plot as a 2 × 2 factorial of trim age and treatment and subplot of post-grind age. ResultsThe Statistical Analysis showed that the coliform concentration increased in function of the storage period 7, 14, 21 d for 24 to 48 h LA treatments and 24 to 48 h control (P 0.05). ConclusionBased on the results, E. coli was not reduced in the samples treated with LA at 2 to 3% prior grinding after 7 and 14 d stored. However, an E. coli reduction was observed over a period of 21 d. Similarly, coliforms counts were not reduced with the chemical treatment during the storage periods.