Aims: To investigate the effect of anionic polysaccharides often used in beverage applications (xanthan and λ-carrageenan) on the antimicrobial efficacy of the cationic surfactant lauric arginate (LAE) against typical spoilage yeasts.
Methods and results: The antimicrobial efficacy of LAE against Saccharomyces cerevisiae, Candida albicans and Zygosaccharomyces bailii in the absence and presence of anionic polysaccharides was assessed by microtitre and macrobroth dilution assays. Combining LAE with either xanthan or λ-carrageenan caused a pronounced decrease in LAE's antimicrobial efficacy, with the minimal inhibitory and lethal concentrations (MIC and MLC) both increasing with increasing polysaccharide concentration. This reduction in antimicrobial efficacy was more pronounced for the addition of λ-carrageenan. To determine the cause of loss of activity, physical properties of solutions were examined. Turbidity and sedimentation measurements indicated that complexes between LAE and anionic polysaccharides had been formed. Electrophoresis measurements showed that complexes had varying electrical charges and dimensions depending on solution composition.
Conclusion: Results suggest that electrostatic interactions between LAE and anionic polysaccharides play a major role in complex formation and loss of antimicrobial activity.
Significance and impact of the study: Results have important implications for the utilization of LAE as an antimicrobial agent in beverage and food products containing anionic polysaccharides.
Keywords: antimicrobials; carrageenan; electrostatic complexation; lauric arginate; spoilage yeasts; xanthan.
© 2014 The Society for Applied Microbiology.