Short communication Yeast biota associated to naturally fermented table olives from different Italian cultivars Rosanna Tofalo ⁎, Giorgia Perpetuini, Maria Schirone, Giovanna Suzzi, Aldo Corsetti Dipartimento Scienze degli Alimenti, Università degli Studi di Teramo, Via C.R. Lerici 1, 64023 Mosciano Sant'Angelo (TE), Italy abstract article info Article history: Received 31 July 2012 Received in revised form 27 November 2012 Accepted 6 December 2012 Available online 28 December 2012 Keywords: Yeasts population PCR-DGGE Technological properties Italian table olives The yeast communities associated with the fermentation of six different cultivars of Italian table olives were stud- ied. Molecular identification of a total of 117 isolates was achieved by a combination of PCR-RFLP of the 5.8S ITS rRNA region and sequencing of the D1/D2 domain of the 26S rRNA gene. In addition, the isolates were differenti- ated by RAPD-PCR. The yeast population was also monitored by a culture-independent method based on PCR-DGGE analysis. This combined strategy resulted to be a powerful and reliable tool to investigate table olives yeast ecology and revealed that Saccharomyces cerevisiae was present in all the processed olives. Moreover, strains were characterized on the basis of different properties of technological interest. In particular, β-glucosidase, cata- lase, pectinolytic, xylanolytic, esterase and lipase activities were investigated and the ability to grow up in presence of different salt concentration (5–7.5–10–14–20% w/v) was evaluated. The majority of strains showed catalase ac- tivity and none of them expressed pectinolytic, xylanolytic, esterase or lipase activities. Six strains belonging to Pichia galeiformis and six strains of Wicheramomyces anomalus showed β-glucosidase activity. Only 10 S. cerevisiae strains were able to grow in presence of 14% NaCl. The obtained results offer valuable information on yeast popu- lation biodiversity and dynamics in naturally fermented Italian table olives and show the potential use of some yeast strains, besides lactic acid bacteria, as a part of mixed starter cultures for table olive fermentation. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Table olives are currently the most important fermented vegeta- ble produced in the developed world. Either as an appetizer accom- panying alcoholic and non-alcoholic beverages or in salads, pizzas and Mediterranean-style meals, table olives are highly appreciated for both their sensory characteristics and nutritive value, and their use is extensive in all markets (IOOC, 2011; Marsilio et al., 2005). According to IOOC (2008) table olives are the product “prepared from the sound fruits of varieties of the cultivated olive tree (Olea europaea L.) which are chosen for their production olives whose volume, shape, flesh-to-stone ratio, fine flesh, taste, firm- ness and ease of detachment from the stone make them particularly suitable for processing.” The most significant production methods of table olives are the Spanish-style and the Californian style involving both a de-bittering process with sodium hydroxide solu- tions (Gómez et al., 2006) and the Greek style for black olives which ferment after immersion in brine without any preliminary treat- ment (natural fermentation) (Tofalo et al., 2012a). Besides these classical processing methods different kinds of traditional methods are also used. For instance, in Marche region (Central Italy) olives known as “Ascolana tenera” are largely produced by local growers. They are hand harvested from mid-September to mid-October when they have reached a yellowish-green surface colour. These kinds of olives are now well known worldwide as a stoned olive fruit stuffed with assorted minced meats and vegetables and dipped in breadcrumbs before frying (Marsilio et al., 2005). In Italy table olives rep- resent one of the most famous fermented vegetables. In fact, three culti- vars have enjoyed Protected Denomination Origin (PDO) status: Bella di Cerignola, in 2000, with the full name “Bella della Daunia olives variety Bella di Cerignola” (Regulation EC No 1904/2000), “Nocellara del Belice,” in 1998 (Regulation EC No 134/1998) (Tofalo et al., 2012a); “Ascolana del Piceno,” in 2006 (Regulation EC No 46/2006). Table olives represent a complex habitat where Lactic Acid Bacte- ria (LAB) and yeasts co-interact and develop throughout the process. As a result, olives acquire the organoleptic qualities afforded by the local environment which includes the presence of the adventitious microbiota that grows during fermentation (Garrido-Fernández et al., 1997). Moreover, the conditions prevailing in this habitat deter- mine the metabolic activity, growth and survival of yeast population (Arroyo-López et al., 2006; Coton et al., 2006; Hurtado et al., 2008; Nychas et al., 2002). Microbiological studies revealed that the species of yeast mainly present in this ecological niche belong to the genera Saccharomyces, Pichia, Debaryomyces and Candida (Arroyo-López et al., 2008). Yeasts can play a double role during olive fermentation, in fact they are associated with the production of volatile compounds (e.g. alco- hols, ethyl acetate, acetaldehyde) and metabolites that improve the taste and aroma and the preservation characteristics of this fermented food. Moreover, they can enhance LAB growth by the release of nutritive compounds (Alves et al., 2012; Arroyo-López et al., 2008; Hernández et al., 2007). On the other hand, yeasts may cause gas-pocket formation, International Journal of Food Microbiology 161 (2013) 203–208 ⁎ Corresponding author. Tel.: +39 0861 266911; fax: +39 0861 266915. E-mail address: rtofalo@unite.it (R. Tofalo). 0168-1605/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.ijfoodmicro.2012.12.011 Contents lists available at SciVerse ScienceDirect International Journal of Food Microbiology journal homepage: www.elsevier.com/locate/ijfoodmicro