Effect of plant material, processing and storage of ramson (Allium ursinum L.) on allicin concentration and antibacterial effect against L. monocytogenes, S. typhimurium and E. coli

Summary

Ramsons (Allium ursinum L.) are known to contain compounds with antibacterial activity and may thus be of interest as an alternative preservation ingredient to protect against pathogenic bacteria in food products. In this study we investigated how the concentration of allicin varies with different plant organs, bulbs, stems, leaves, flowers and how bulb size affect the concentration. Furthermore we examined the effect of processing of bulbs into four products on allicin content. Products that potentially could be used as a preservation ingredient: freeze dried milled powder, oven dried milled powder, wet grinded pesto, wet grinded pesto with pasteurization. The four products were tested for allicin content after long term storage for up to 1.5 years at -20°C. Short term storage of dry ramson powder for 1 month at four different temperatures from -20°C to +40°C was also studied. We also investigated the effect of different plant organs, processing and long term storage of ramson on the antibacterial activity of processed bulbs against Salmonella typhimurium, Listeria monocytogenes and Escherichia coli in a BHI growth inhibition model. Results showed that bulbs and flowers have a higher concentration of allicin than leaves and stems and also display higher inhibitory activity against growth of all three bacteria strains. Allicin content on a dry weight basis was low in small bulbs and increases up to 4 g bulb size after which no further increase was seen. Allicin concentration was highest in freeze dried and oven dried milled products followed by wet grinded product and the wet grinded pasteurized product had the lowest concentration. One month storage at between -20° to +40° did not significantly alter the concentration of allicin in dry ramson powder. All processed bulb products showed strong antibacterial effects against all three bacteria strains in the BHI growth inhibition model and with little or no change over 1.5 years of storage. The effect against Salmonella and E. coli was stronger than against Listeria. The results suggest that ramson products may potentially be used as an alternative to preserve organic and conventional meat products. However, documentation in final meat products need to be obtained before any recommendations can be given.