Active polymers containing Lactobacillus curvatus CRL705 bacteriocins: effectiveness assessment in Wieners.

Bacteriocins from lactic acid bacteria have potential as natural food preservatives. In this study two active (synthetic and gluten) films were obtained by the incorporation of lactocin 705 and lactocin AL705, bacteriocins produced by Lactobacillus curvatus CRL705 with antimicrobial activity against spoilage lactic acid bacteria and Listeria. Antimicrobial film effectiveness was determined in Wieners inoculated with Lactobacillus plantarum CRL691 and Listeria innocua 7 (10(4)CFU/g) stored at 5°C during 45days. Active and control (absence of bacteriocins) packages were prepared and bacterial counts in selective media were carried out. Visual inspection and pH measurement of Wieners were also performed. Typical growth of both inoculated microorganisms was observed in control packages which reached 10(6)-10(7)CFU/g at the end of storage period. In the active packages, L. innocua 7 was effectively inhibited (2.5 log cycles reduction at day 45), while L. plantarum CRL691 was only slightly inhibited (0.5 log cycles) up to the second week of storage, then counts around 10(6)-10(7)CFU/g were reached. Changes in pH values from 6.3 to 5.8 were produced and gas formation was observed in active and control packages. The low inhibitory effectiveness against lactic acid bacteria is in correlation with the low activity observed for lactocin 705 in the presence of fat; Wieners fat content (20-30%) may adversely affect antimicrobial activity. This study supports the feasibility of using polymers activated with L. curvatus CRL705 bacteriocins to control Listeria on the surface of Wieners and highlights the importance of evaluating antimicrobial packaging systems for each particular food application.

Inhibition of Listeria innocua and Brochothrix thermosphacta in vacuum-packaged meat by addition of bacteriocinogenic Lactobacillus curvatus CRL705 and its bacteriocins.

AIMS: To evaluate the inhibition effectiveness of Lactobacillus curvatus CRL705 used as a bioprotective culture and of its bacteriocins, lactocin 705 and lactocin AL705, against Listeria innocua, Brochothrix thermosphacta and indigenous lactic acid bacteria (LAB) in vacuum-packaged meat stored at 2 degrees C. METHODS AND RESULTS: The live culture of Lact. curvatus CRL705 as well as synthetic lactocin 705 and purified lactocin AL705 were shown to be similarly effective in preventing the growth of B. thermosphacta and L. innocua in meat discs in contrast to control samples in which these micro-organisms grew rapidly, their numbers increasing by 3.0- and 2.1-log cycles respectively. In addition, indigenous LAB population showed a lower growth rate in the presence of lactocin 705. Bacteriocin activity was detected in the meat discs during 36 days at 2 degrees C irrespective of the biopreservation strategy applied. Changes in pH were not significantly different in meat discs treated with the protective culture when compared with control samples. CONCLUSIONS: Lactobacillus curvatus CRL705 and the produced bacteriocins, lactocin 705 and lactocin AL 705, were effective in inhibiting L. innocua and B. thermosphacta. The use of the bioprotective culture in refrigerated vacuum-packaged fresh meat would be more feasible from an economic and legal point of view. SIGNIFICANCE AND IMPACT OF THE STUDY: Establishment of biopreservation as a method to ensure the microbiological safety of vacuum-packaged fresh meat at 2 degrees C.