Antimicrobial Activity of Processed Spices Used in Traditional Southern Italian Sausage Processing

Several spices are used to process ‘Nduja, a traditional Calabrian sausage, well known for its typical flavor and piquancy. Despite wide use of spices for meat curing and controlling undesired microorganisms, no studies reported antimicrobial effectiveness of the spices in the ‘Nduja processing. The aim of this work was to evaluate the antimicrobial activities against 10 foodborne pathogens of processed spices used in the ‘Nduja industrial manufacturing. Spice extracts (using ethanol, methanol and water as solvents) were investigated by disk diffusion assay for their antimicrobial activity. Methanol extracts showed the best results, mainly against Bacillus cereus strains. Thus, they were further evaluated, through microdilution automated spectrofluorimetric absorbance readings. Many spice methanol extracts showed low antimicrobial activities, although B. cereus strains were still more sensitive. In addition, two out of the three spice mixtures showed medium and high inhibition activity against Escherichia coli ATCC 35401 and Yersinia enterocolitica DSM 4780, respectively. Practical Applications Recently, the use of natural compounds such as antimicrobial peptides, plant essential oils and spice extracts has been proposed to control both food spoilage and pathogenic microorganisms. The knowledge of the antimicrobial effect played by processed spices and spice mixtures employed for ‘Nduja curing could contribute to improve the microbial quality of this traditional sausage. However, the result of the present work indicated that processed spices exerted a negligible inhibition of foodborne pathogens growth. Thus, the addition of spice mixtures in this food does not assure alone a sufficient level of food safety. Therefore, if processed spices are used as preserving agents in meat processing, their efficacy has to be carefully and preliminarily evaluated by producers case by case.