INDIVIDUAL AND COMBINED LISTERICIDAL EFFECTS OF SODIUM LACTATE, POTASSIUM SORBATE, NISIN AND CURING SALTS AT REFRIGERATION TEMPERATURE

Authors


1 Correspondence to: Dr. Sava Buncic, Meat Industry Research Institute of New Zealand (Inc.), P.O. Box 617, Hamilton, New Zealand.

ABSTRACT

The individual and combined antilisterial activity of the preservatives sodium lactate (4%), potassium sorbate (0.3%) and nisin (400 IU/ml), in either the presence or absence of the curing salts nitrite (125 ppm) and polyphosphate (0.5%), was assessed in buffered BHI broth (pH 5.5) during incubation at 4C. A cocktail of the strain Listeria monocytogenes NCTC 7973 and two food derived strains was used as the inoculum in challenge studies. In the absence of the preservatives, L. monocytogenes grew in the presence of polyphosphate but not in the presence of nitrite or a combination of nitrite and polyphosphate. The antilisterial action of nitrite was predominantly bacteriostatic in nature. Lactate acting alone, or in the presence of curing salts, produced a bacteriostatic effect. Sorbate acting alone had a bacteriostatic effect. Sorbate acting in the presence of nitrite or nitrite and polyphosphate produced a marked listericidal effect, reducing the population by 6.7 logs and 5.4 logs, respectively. Nisin acting alone produced an almost immediate 90% listericidal response (1 log population decrease), but initial numbers were restored within 14 days by regrowth. Regrowth was eliminated when nisin was used in combination with lactate, nitrite or nitrite and polyphosphate. The combination of lactate and sorbate offered no advantage over the use of sorbate alone. Sorbate and nisin acting in combination produced an enhanced listericidal effect, which was also seen in the presence of curing salts, but was delayed. No listericidal advantage over sorbate-nisin combination was achieved through the use of the lactate-sorbate-nisin combination. The combined use of sorbate and nisin offers promise as a means of eliminating L. monocytogenes from low pH cured meat products. The efficacy of this preservative combination remains to be evaluated in a meat system before its practical application can be considered.

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