Antimicrobial efficacies of plant extracts and sodium nitrite against Clostridium botulinum

This study was conducted to evaluate the antibotulinal activities of some plant extracts, alone or in combination with nitrite (NaNO2). Water- and 99.5% ethanol-soluble extracts (1:9 plant material weight-by-solvent volume, 25 °C, 48 h) of 90 kinds of fresh and dehydrated herbs and spices were tested. The aqueous extract of clove and alcohol extracts of lemon eucalyptus, mace and licorice exhibited greater antibotulinal activities in TPGY medium with MIC ranging from 0.05% to 0.2%. However in TPGY, only the aqueous extract of Coptis rhizome exhibited synergistic antibotulinal activity with NaNO2, reducing the individual MIC of NaNO2 from 6–8 ppm to 2 ppm with 0.05% Coptis extract. In a model meat food, the alcohol-soluble extracts of nutmeg (0.05%) and sage (0.02%), and the aqueous fraction of clove extract (0.05%) exhibited antibotulinal activities in combination with 10 ppm NaNO2. The observed synergy between plant extracts and NaNO2 that resulted in lower MIC of both additives have significant repercussion in the control of botulism in minimally processed meat products without compromising organoleptic properties.