M: Food Microbiology & Safety Antimicrobial Activity against Beneficial Microorganisms and Chemical Composition of Essential Oil of Mentha suaveolens ssp. insularis Grown in Sardinia Giacomo Luigi Petretto, ∗ Francesco Fancello, ∗ Severino Zara, Marzia Foddai, Nicoletta P. Mangia, Maria Lina Sanna, Elasyed A. Omer, Luigi Menghini, Mario Chessa, and Giorgio Pintore Abstract: The aim of this work was to determine the chemical constituents and in vitro antimicrobial activity of the essential oil (EO) of the aerial parts of Mentha sueveolens spp. insularis grown in Sardinia (Italy) against probiotic and starter microorganisms. The gas chromatography-mass spectrometry (GC-MS) analysis allowed to identified 34 compounds, most of oxygenated monoterpene compounds (82.5%) and among them, pulegone was found as major compound (46.5%). The agar diffusion test carried out employing the EO of Mentha suaveolens spp. insularis showed a low antibacterial activity, in particular no action was noticed for probiotic bacteria belonging to lactic acid bacteria groups, whereas almost all yeasts strains tested were inhibited. The automated microtitter dilution assay showed a clear effect at increasing concentration of EO on the specific growth rate (μ) and extension of the lag phase (λ) only for S. xylosus SA23 among bacteria and for Saccharomyces cerevisiae, Tetrapisispora phaffii CBS 4417, Metschnikowia pulcherrima, and Candida zemplinina among yeasts. Results obtained in this work allow us to broaden the knowledge on the effect of EOs on probiotic and food-related microorganisms. Keywords: essential oil, fermented food, GC-MS, probiotic bacteria, yeasts Practical Application: Mentha suaveolens spp. insularis may be used in combination with probiotic bacteria into the food matrix or encapsulated in coating and edible films for food preservation. Introduction The essential oils (EOs), long been recognized to have antimi- crobial properties, counteract the growth of bacteria, yeast, and molds and have been extensively tested in vitro against a wide range of pathogenic bacteria and fungi (Kalemba and Kunicka 2003). EOs are generally obtained by distillation from various plant source and the genus Mentha sp. (Lamiaceae, family) is an important source of basic raw materials to obtain EOs. Biological and antimicrobial activity of EO extracted from various plants of mint genus has been deeply investigated (that is, Mentha pulegium EO, Mentha longifolia EO, peppermint oil, spearmint oil). How- ever, many of them are not yet completely exploited. Recently, great attention has been given to food preservation methods and alternatives to the antibiotics for the control of po- tential pathogens in the animal gastrointestinal tract using healthy natural products such as EOs (Burt 2004; Hayouni and others 2010). Food preservatives based on EOs are becoming very inter- esting and their antimicrobial activity has been widely studied in MS 20130783 Submitted 6/10/2013, Accepted 11/19/2013. Authors Petretto, Foddai, Chessa, and Pintore are with Dipartimento di Chimica e Farmacia, Univ. di Sassari, 07100, Italy. Authors Fancello, Zara, Mangia, and Sanna are with Dipartimento di Agraria, Univ. di Sassari, 07100, Italy. Author Omer is with Medicinal and Aromatic Plants Research Dept, Natl. Research Centre, EL Bohouth St., Dokki, Giza, Cairo, 12622, Egypt. Author Menghini is with Dipartimento di Farmacia, Univ. di Chieti, Pescara, Italy. Direct inquiries to author Pintore (E-mail: pintore@uniss.it). ∗ These authors contributed equally to this work. liquid, vapor phase and by bio-based active packaging materials such as coating and edible films (Devlieghere and others 2004; L´ opez-Rubio and others 2004; Emiro˘ glu and others 2010). Regarding the control of pathogens in animal gastrointestinal tract, a number of approaches have been suggested, such as the use of probiotics and EOs as feed additives (Hammer and others 1999). Moreover, in clinical setting, topical use of EOs is the most promising strategy for both skin and mucous membranes (Low and others 2011). Lactic acid bacteria (LAB) and yeasts play an important role in fermentation processes. These may be naturally present in fermented foods either because added as starter or as adjuncts starter cultures to obtain fermented foods. Besides LAB and yeasts are also members of human microbiota (are in fact present in the gastrointestinal tract, skin and the oral cavity micro- biota) and different strains of these species are used as probi- otics, namely microorganisms which, when administered in ade- quate amounts, confer a health benefit on the host (FAO/WHO 2001). Few works have explored the behavior of beneficial mi- croorganisms when incubated with EOs (Hayouni and others 2008), although few authors found that some spices can stimu- late the growth of some LAB (Zaika and Kissinger 1981; Nes and Skjelkale 1982). Mentha suaveolens, commonly known as apple mint, has been used as traditional folk medicine. The species M. suaveolens is cur- rently divided into 2 subspecies: suaveolens and insularis. M. suave- olens spp. suaveolens have been widely studied by several authors (Ouzmil and others 2002; Benayad and others 2012), whereas C  2014 Institute of Food Technologists R  doi: 10.1111/1750-3841.12343 Vol. 79, Nr. 3, 2014  Journal of Food Science M369 Further reproduction without permission is prohibited