Exploratory use of nisin and ethyl lauroyl arginate for the inhibition of spoilage microflora during secondary shelf life

After opening a food package, an acceleration of degradative phenomena and food spoilage occurs, leading to a short useful period for consumption after opening, which is the secondary shelf life (SSL). A short SSL often causes the inability to fully consume the product, contributing to the generation of household food waste. Our study explores the possible application of antimicrobial compounds, through release after package opening, aimed at extending the SSL, with the potential of lowering waste generated at the household level. A simulation of domestic use of an almond-based beverage was performed in ten different real household environments. Upon occurrence of alteration, the environmental spoilage microflora (unidentified microbial mixes) was transferred and stored in liquid media for subsequent antimicrobial testing. The disk-diffusion agar method was conducted on the ten mixes using nisin (100-1250 µg/mL), ethyl lauroyl arginate (LAE) (0.1-5%) and lysozyme (100-800 µg/mL) as antimicrobial compounds. In addition, the stability of the active compounds in chloroform at 70°C for 1 h was tested, foreseeing a possible inclusion within film forming solutions. Results highlighted that microbial inhibition depended on the spoilage bacteria mix and on the microbial compounds. LAE showed the highest antimicrobial effectiveness towards all the target mixes, followed by nisin which inhibited only five out of ten mixes; on the other hand, lysozyme showed no inhibition, irrespective of microbial mix and tested concentration. The partial inhibition of the different bacteria mixes is due to their heterogeneous composition, which reflects the environmental contamination of the different households. Nisin and LAE maintained effectiveness after treatment with chloroform, even at high temperatures, thus paving the way towards the incorporation of these antimicrobials as potential active compounds in polymer matrices, for controlled release during domestic storage.