Control of listeria in meat emulsions by combinations of antimicrobials of different solubilities

- Lauric arginate, sodium lactate, and methylparaben can be incorporated in an emulsion type sausage matrix without causing structural alterations.
- Binary combinations of these antimicrobials show good efficacies against L. innocua.
- Addition of a third component above a critical concentration to form ternary combinations may further enhance efficacy.

The antimicrobial efficacy of three antimicrobials with different aqueous solubilities (sodium lactate > lauric arginate (Nα-lauroyl-l-arginine ethyl ester, LAE > methylparaben)) was evaluated. The antimicrobials were added individually, and as binary or ternary mixtures to emulsion type sausages. The antimicrobial efficacy was evaluated against Listeria innocua on the surface of sliced sausages over 24 days of storage at 6 °C. Growth over time was determined, and fitted to a model with a shifted logistic function for evaluation and comparison of antimicrobial effectiveness. The maximum added concentration of LAE (2.0 × 103 μg/g) delayed growth for 1 day. In contrast, lactate and methylparaben (40 and 4.0 × 103 μg/g, respectively) delayed growth for 18 and 7 days, respectively. Five different mixing ratios were investigated for the three different binary combinations: LAE/lactate, LAE/methylparaben and lactate/methylparaben. Results showed that efficacy could be enhanced through mixing of antimicrobials and that the type of antimicrobials as well as their mixing ratio influenced the antimicrobial efficacy of combinations. For ternary combinations, concentrations of two antimicrobials were kept constant while the concentration of the third preservative was varied. To this purpose LAE/methylparaben, LAE/lactate and lactate/methylparaben combinations with concentrations of 0.3/3.3, 0.3/16.7 and 6.6/2.7 × 103 μg/g, respectively, were combined with increasing concentrations of lactate, methylparaben and LAE, respectively. Results indicated that a further increase in activity is possible, albeit there appears to be a critical concentration of the third component below which the ternary combinations were less effective than the binary combinations. Overall our study suggests that combining antimicrobials with different solubilities is a promising approach to enhance shelf life of structurally-complex products such as emulsion type sausages.