REDUCTION OF BROCHOTHRIX-THERMOSPHACTA ON BEEF SURFACES FOLLOWING IMMOBILIZATION OF NISIN IN CALCIUM ALGINATE GELS

Lean and adipose beef carcass tissues inoculated with Brochothrix ther mosphacta (BT) (approx. 4.50 log(10) cfu cm(-2)) were left untreated ( U) or treated with 100 mu g ml(-1) nisin (N), calcium alginate (A) or 100 mu g ml(-1) nisin immobilized in a calcium alginate gel(AN). Tissu e samples were refrigerated after treatments and bacterial populations and nisin activity were determined at 0, 1, 2 and 7 d. U, A and N tre atments 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 titres from both tissues were higher in AN vs N sample s after the 7 d incubation. This study demonstrates that immobilizatio n of nisin in a gel may be a more effective delivery system of a bacte riocin to the carcass surface than direct application.