Antimicrobial activity of cinnamon and clove oils under modified atmosphere conditions

Mixtures of cinnamon and clove oils were tested for inhibitory activity against important spoilage microorganism of intermediate moisture foods. Four fungal species (Aspergillus flavus, Penicillium roqueforti, Mucor plumbeus and Eurotium sp.), four yeasts species (Debaryomyces hansenii, Pichia membranaefaciens, Zygosaccharomyces rouxii and Candida lipolytica), and two bacteria species (Staphylococcus aureus and Pediococcus halophilus) inoculated separately on agar plates were sealed in a barrier pouch and exposed to essential oil volatiles under a modified at mosphere of low O2 (< 0.05–10%) and high CO2 (20% or 40%), with the balance being N2. A. flavus and Eurotium sp. proved to be the most resistant microorganisms. Cinnamon and clove oils added between 1000 and 4000 μL at a ratio of 1:1 were tested for minimum inhibitory volume (MIV) against molds and yeasts. The gas phase above 1000 μL of the oil mixture inhibited growth of C. lipolytica and P. membranaefaciens; 2000 μL inhibited growth of A. flavus, P. roqueforti, M. plumbeus, Eurotium sp., D. hansenii, and Z. rouxii, while inhibition of A. flavus required the addition of 4000 μL. Higher ratios of cinnamon oil/clove oil were more effective for inhibiting the growth of A. flavus.