Inhibition of spoilage and pathogenic bacteria associated with foods by combinations of antimicrobial agents

The antibacterial activity of combinations of lysozyme, monolaurin (ML), triglycerol 1,2 laurate (TGL) and butylated hydroxyanizole (BHA) against 7 Gram-positive and 8 Gram-negative bacteria was studied at different pH, NaCl and EDTA concentrations by the spiral gradient endpoint test. The inhibitory effect of lysozyme in combination with ML was slightly greater for Gram-positive than for Gram-negative bacteria, but their combined effect was not markedly more inhibitory than ML alone. Lysozyme and TGL together were only inhibitory at low pH and high NaCl concentrations in the presence of EDTA. There was an increase in inhibition when lysozyme and BHA were combined. For Grampositive bacteria, inhibition by ML and BHA together was more marked than when either was present singly. However, ML decreased the antibacterial activity of BHA against Gram-negative bacteria. Similarly, TGL was antagonistic to BHA action against both Gram-positive and Gram-negative bacteria. In general, the inhibition produced by all combinations was greater as the pH decreased and the NaCl concentration increased, especially in the presence of EDTA.