Effect of Mexican Oregano (L ippia berlandieri Schauer) Essential Oil Fractions on the Growth of A spergillus spp. in a Bread Model System

Abstract

Spices acting as antimicrobial agents can be used in combination with other factors to assure food safety. The aim of this work was to evaluate the effect of Mexican oregano (Lippia berlandieri Schauer) essential oil (EO) fractions on the growth of Aspergillus spp. using a bread model media. Fungal growth was evaluated on a wheat flour-based medium with controlled Aw (0.925, 0.950) and with five Mexican oregano EO fractions with different concentrations of thymol and carvacrol (50–200 mg/kg). Fungal growth (modified Gompertz equation) was affected by Aw values and the concentration of Mexican oregano EO fractions. Differences on thymol and carvacrol had no significant effect on the fungal growth kinetic parameters. Low Aw (0.925) and fractions with high concentration of carvacrol (1 and 2) at 100 mg/kg showed fungicidal activity. Combined methods for food preservation can include Mexican oregano EO, where Aspergillus spp. fungal growth can be inhibited. Practical Applications Incorporation of herbs and essential oils to food products can be considered as a good form to increase shelf life of the product, but usually data on antimicrobial and/or antioxidant capacity are performed under laboratory-controlled conditions. The development of predictive models that consider the effect of the food components on the effectiveness of natural antimicrobials can lead to a better understanding of the best conditions for their addition to food products. The present work describes the effect of water activity and wheat components on the antifungal activity of Mexican oregano essential oil. The composition of the essential oil and its concentration were tested in combination with water activity, and it was observed that those factors greatly affected the biological activity of the essential oil.