No abstract

-Thirteen dairy propionibacteria were screened for catalase-insensitive, protease-sensitive inhibition of various Gram-positive and Gram-negative bacteria. Production of bacteriocin-like agents was identified in 8 ofthese cultures. The bacteriocin produced by Propionibacteriumjensenii B 1264 inhibited closely related propionibacteria and lactic acid bacteria and was bactericidal to Lactobacillus delbrueckii subsp. lactis ATCC 4797. It was produced in sodium lactate broth cultures during stationary phase; maximum activity was detected after 10 d of growth but only after IO-fold concentration of culture supematants. The bacteriocin was precipated by ammonium sulphate at 70 % saturation. The ammonium sulphate-concentrated, dialyzed bacteriocin was stable to 0.1-1.0 rnol-Lr' NaCI, 0.1-2.0 % SOS, 4 mol-L:' urea, 100 "C (60 min), pH 2-10 and organic sol vents (methanol, ethanol and isopropanol at 0-50 %). Batch anion exchange chromatography (pH 6.5) of the bacteriocin yielded 101 % activity and 15-fold increased purity. Flat bed analytical isoelectric focussing showed that the isoelectric point was between pH 3 and 3.5. SOS-PAGE yielded an estimated molecular mass between 6 and 9 kOa. The evidence suggests that this anionic bacteriocin is unique. © Inra/Eisevier, Paris.

A culture of the psychotrophic strain FloraCarn L-2 of Lactobacillus alimentarius was added to ground beef (pH 5.4) inoculated with two isolates of Listeria monocytogenes able to grow in refrigerated ground beef. The ground beef was vacuum-packaged and stored for 9 weeks at 4 degrees C. Populations of inoculated L. monocytogenes initially were 6.3 to 6.4 log10 CFU/g and increased to 7.4 log10 CFU/g in ground beef with no added lactobacilli. Addition of L. alimentarius L-2 or its antibiotic-resistant mutant SRL-2 reduced the final populations of L. monocytogenes to 4.3 or 4.1 log10 CFU/g, respectively. L. alimentarius L-2 did not produce bacteriocins or hydrogen peroxide in vitro. The antilisterial effect of L. alimentarius observed in laboratory media and ground beef is attributed to lactic acid (ca. 50 mM) produced by growing cultures.

Bacterial counts were compared for samples from three groups of beef from two different sources. Group 1 samples were from choice forequarters as received, then sprayed with HOC1 (200 mg/L, pH 6.0-6.5, 7.03 kg/cm*, 12 set at 16°C). Group 2 samples served as controls and were from choice forequarters from the same lot as group 1 but not sprayed. Group 3 samples were from frozen boneless lean domestic and imported beef, Surface strip and ground beef samples from groups 1 and 2 had aerobic plate counts (APC) and lactic acid bacteria counts (LABC) that were not significantly different, P < 0.001. Conversely, strip and ground beef samples from group 3 had APC and LABC that were significantly higher, P > 0.001, than those for the control, group 2, samples. Also, the coliform and coagulase positive S. uureus counts were also significantly higher for the group 3 ground beef samples. Thus, the hypochlorous acid spray treatment of beef forequarters did not appear to yield ground beef with better bacteriological quality than the unsprayed forequarters from the same source, perhaps because the initial bacterial count was already so low. The higher surface APC of the lean boneless beef, group 3, was reflected in the higher initial APC of the ground beef prepared from that source.

Pectoral muscle cubes from 10-week old broilers were “water-washed” or “salt-washed” ( 0.6 M NaCl) to provide tissue with various quantities of water-soluble and salt-soluble proteins. Approximately 30% of the water-soluble protein was removed when cubes were water-washed. Salt-washed cubes had decreases of 42% and 54% in salt-soluble and water-soluble protein concentrations, respectively. Loaves prepared with meat from the two washing treatments and control cubes showed significant (P&lt;0.01) differences in both cooking loss and binding strength of meat slices. The quantity of salt-soluble proteins available for solubilization to reduce cooking loss and increase binding strength among meat particles appeared more important to poultry loaf processing than the quantity of extractable water-soluble proteins.