Purpose: We hypothesized that a suitable approach to improve the antimicrobial activity of LAE in complex food matrices is to combine this structure-sensitive component with a less structure-sensitive preservative that may attack different cellular levels and to examine the efficacy of this combination in a modified model system that contains bovine serum albumin (BSA) as an interacting agent.
Methods: Minimal lethal concentrations (MLC) of LAE (1 wt% LAE and 1 wt% Tween 80 in pure water; pH 6) against Listeria innocua LTH 3096 (inoculation level: 102 CFU/ml; nutrient broth) in the presence of 0 - 2 wt% BSA (pH 6) and/or 0 - 0.25 wt% methylparaben (pH 6) were determined using plate counts (detection limit: 102 CFU/ml; n = 4). Measurements were carried out over 12 days at 4°C to simulate typical storage conditions of meat products.
Results: While the presence of 2 wt% BSA significantly increased the MLC of LAE against L. innocua from 20 to 200/225 µg/ml, the antimicrobial activity of methylparaben was not strongly influenced by the protein content. In both assays (± BSA) 1000 µg/ml methylparaben caused a reduction in viable cell concentration of ca. 6 log. However, a slightly lower MLC of ~2500 µg/ml was detected in systems without BSA addition. Combinations were found to be synergistic and the presence of only 1000 µg/ml methylparaben remarkably reduced the concentration of LAE needed to cause total growth inhibition in model assays (± BSA).
Significance: The combination has great potential for meat applications and may thus be of interest to the meat industry.