EFFECT OF MEXICAN OREGANO (LIPPIA BERLANDIERI SCHAUER) ESSENTIAL OIL FRACTIONS ON THE GROWTH OF ASPERGILLUS SPP. IN A BREAD MODEL SYSTEM RAÚL ÁVILA SOSA SÁNCHEZ 1 , MARTHA C. PORTILLO-RUIZ 2 , SABINA VIRAMONTES-RAMOS 2 , LAILA N. MUÑOZ-CASTELLANOS 2 and GUADALUPE V. NEVÁREZ-MOORILLÓN 2,3 1 Facultad de Ciencias Químicas, Benemérita Universidad Autónoma de Puebla, Puebla, Puebla, México 2 Facultad de Ciencias Químicas, Universidad Autónoma de Chihuahua, PO Box 1542-C, Chihuahua, Chihuahua, México 3 Corresponding author. TEL: (52) 614-236-6000 ext. 4248; FAX: (52) 614-236-6000; EMAIL: vnevare@uach.mx Received for Publication March 2, 2014 Accepted for Publication April 29, 2014 doi:10.1111/jfpp.12287 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 evalu- ated 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. Dif- ferences on thymol and carvacrol had no significant effect on the fungal growth kinetic parameters. Low Aw (0.925) and fractions with high concentration of car- vacrol (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 condi- tions. 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 essen- tial 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 essen- tial oil. INTRODUCTION Fungi are responsible for spoilage of foodstuff during storage, with the consequent hazard for food safety, mainly because of mycotoxin contamination. It has been estimated that 5–10% of the world’s food production is lost as a result of fungal spoilage. The ability of fungi to grow in food depends on a variety of factors including water activity, pH and nutrient availability (Bluma et al. 2008; Rouse et al. 2008; Aoudou et al. 2011). Cereal-based foods, especially bread, can be contami- nated and spoiled by molds. Fungal growth on those food products can be observed visually by the production of unpleasant flavors and odors (Marín et al. 2002; Arroyo et al. 2005; Astoreca et al. 2012). Spoilage fungi that com- monly contaminate bakery products include xerophilic species of Aspergillus, Eurotium, Penicillium, Cladosporium, Mucor, Rhizopus and Neurospora genera and Wallemia sebi (Vytrasova et al. 2002; Smith et al. 2004; Guynot et al. 2005; González-Chávez et al. 2011). Journal of Food Processing and Preservation ISSN 1745-4549 Journal of Food Processing and Preservation •• (2014) ••–•• © 2014 Wiley Periodicals, Inc. 1