Submitted to: Letters in Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 12, 1995
Publication Date: N/A
Interpretive Summary: This research demonstrates that applying nisin in an edible film (calcium alginate gel) to the surface of meat significantly enhances the inhibition of Brochothrix thermosphacta as compared to applying nisin directly to meat surfaces. B. thermosphacta is a major source of spoilage of vacuum packaged meat. Nisin is a bacteriocin (naturally occurring antibacterial protein) that has the potential for use as a meat preservative. Nisin inhibits many meat spoilage bacteria and the pathogens Listeria monocytogenes and Clostridium botulinum. Samples treated with nisin in the edible gel were 99% more effective at inhibiting B. thermosphacta on meat than nisin applied alone. Calcium alginate and untreated controls did not reduce B. thermosphacta. Applying nisin in an edible gel not only offers an enhanced antimicrobial effect from nisin, but this same gel has been demonstrated to reduce shrink loss from animal carcasses. Nisin is approved for use in processed cheeses to kill Cl. botulinum which causes botulism. Current costs for nisin are prohibitive at this time; however, as research demonstrates the efficacy of nisin (and other bacteriocins) for use as meat antimicrobials, perhaps cost will no longer be a limiting factor.
Technical Abstract: Lean and adipose beef carcass tissues inoculated with Brochothrix thermosphacta (BT) (approximately 4.50 log**10 CFU/cm**2) were left untreated (U), or treated with 100 ug/ml nisin (N), calcium alginate (A), or 100 ug/ml nisin immobilized in a calcium alginate gel (AN). Tissue samples were refrigerated after treatments and bacterial populations and nisin activity were determined at 0, 1, 2, and 7 days. U, A, and N treatments of lean and adipose tissues did not suppress bacterial growth (>6 log**10 CFU/cm**2 by day 7) while treatments of lean and adipose tissues with AN suppressed bacteria (>2.42 log**10 CFU/cm**2 by day 7). Bacteriocin titers from both tissues were higher in AN versus N samples after the 7 day incubation. This study demonstrates that immobilization of nisin in a gel may be a more effective delivery system of a bacteriocin to the carcass surface than direct application.