Reducing or Preventing Recovery of Injured Listeria monocytogenes on Ready-to-Eat Natural and Organic “Uncured” Processed Meats

Objectives

To investigate the use of natural antimicrobial ingredients and post-lethality interventions that are commercially available and eligible for use in natural and organic processed meat products as means to inhibit the recovery and growth of Listeria monocytogenes (Lm) in naturally-cured, ready-to-eat (RTE) boneless ham and frankfurters stored under refrigeration (4°C) over 98 days.

Conclusions

Of the natural antimicrobial ingredients evaluated, 1% cranberry powder (w/w) was not sufficient to inhibit the growth of Lm to ≤ 2 log CFU/g over 98 days of refrigerated storage compared to initial levels. The other ingredients studied, namely 1% vinegar (w/w) and 2.5% vinegar and lemon juice concentrate (w/w), limited the growth of Lm to ≤ 2 log CFU/g during refrigerated storage compared to initial levels and regardless of product type. None of these ingredients, however, caused initial Lm populations to decrease.

Of the post-lethality interventions investigated, high hydrostatic pressure (400 MPa for 4 min), lauric arginate (44 ppm), and octanoic acid (400 ppm) decreased initial populations of Lm by ≥ 1 log CFU/g compared to an untreated control whereas post-packaging thermal treatment (71°C for 30 s) did not regardless of product type. Nonetheless, by the end of the refrigerated storage period, Lm was able to recover and exhibit significant growth in all of these treatments.

Assessment of the combinations of each of the natural antimicrobial ingredients with each of the post-lethality interventions on the recovery and growth of Lm in naturally cured RTE boneless ham, showed that only when the vinegar or the vinegar and lemon juice concentrate ingredients were combined with the high hydrostatic pressure, the lauric arginate, or the octanoic acid post-lethality interventions were decreases in initial populations and a sustained inhibition of the recovery and growth of Lm achieved during refrigerated storage of the product. Thus, a multipronged approach that employs a post-lethality intervention to reduce initial levels and a natural antimicrobial ingredient to prevent the recovery and subsequent growth of the pathogen Lm represents a proactive measure that could be instituted by makers of natural and organic RTE processed meat products as part of their Lm control plans.

Deliverable

The studies demonstrated that selected natural antimicrobial ingredients and post-lethality interventions currently available to manufacturers of natural and organic ready-to-eat processed meats are effective at addressing the potential presence of Lm on such products. Moreover, the work further substantiated the effectiveness of a multiple hurdle approach for the control of Lm in RTE processed meat products.