Andreia Bianchini, Jayne Stratton, Steve Weier, Carmen Cano and Lucia Miceli Garcia
The antimicrobial activity of 25 essential oils and plant extracts against Salmonella Typhimurium and Penicillium roqueforti was tested by disc diffusion and quantified by agar dilution. Afterwards, the effect of the most promising essential oils was studied in an extruded pet food product over 21 days, with the oil mixed either into the product or as part of its coating. In vitro, the best inhibitors for Salmonella were cinnamon essential oil (EO) at 0.05% and thyme EO at 0.1%, while P. roqueforti was best inhibited by cinnamon EO at 0.01% and spearmint EO at 0.5%. When tested in the extruded product, cinnamon EO (0.05% and 0.1%) and spearmint EO (0.5%) proved ineffective against P. roqueforti, either mixed into the product or as part of its coating. Only cinnamon EO (0.1%) as part of the coating was able to reduce Salmonella significantly faster than the control (p-value=0.0408) during storage for 21 days. Based on the results, spice essential oils can act as inhibitors of Salmonella in a pet food product, when present at a sufficient concentration.