Microbiota and metabolome during controlled and spontaneous fermentation of Nocellara Etnea table olives Cinzia Lucia Randazzo a, * , Aldo Todaro b , Alessandra Pino a , Iole Pitino a , Onofrio Corona b , Cinzia Caggia a a Department of Agricultural, Food and Environment, University of Catania, Italy b Department of Agricultural and Forest Science, University of Palermo, Italy article info Article history: Received 19 July 2016 Received in revised form 12 January 2017 Accepted 28 January 2017 Available online 2 February 2017 Keywords: Table olives Starter cultures VOCs LAB abstract This study is aimed to investigate bacterial community and its dynamics during the fermentation of Nocellara Etnea table olives and to study its effect on metabolome formation. Six different combination of bacterial cultures (BC1-BC6) were used as starters for table olive fermentation and one additional process, conducted without addition of any starters, was used as control (C). The processes were con- ducted in triplicate and, overall, 21 vessels were performed at industrial scale. The fermentation was monitored for 120 days through culture-dependent and eindependent approaches. Microbial counts of the main microbial groups revealed slight differences among brine samples, with the exception of LAB counts and Enterobacteriaceae, which were higher and lower, respectively, in most of the inoculated samples than the control ones. In addition, results demonstrated that the use of bacterial cultures (except the BC1), singly or in different combinations, clearly influenced the fermentation process reducing the final pH value below 4.50. When microbiota was investigated through sequencing analysis, data revealed the presence of halophilic bacteria and, among lactobacilli, the dominance of Lactobacillus plantarum group at the initial stage of fermentation, in all brine samples, except in the BC5 in which dominated Lactobacillus casei group. At 60 and 120 days of fermentation, an overturned bacterial ecology and an increase of biodiversity was observed in all samples, with the occurrence of Lactobacillus paracollinoides, Lactobacillus acidipiscis and Pediococcus parvulus. Correlation between bacterial OTU and volatile organic compounds (VOCs) revealed that, aldehydes and alcohol compounds exhibited a positive correlation with Proteobacteria, while several esters with LAB and Hafnia. In particular, esters, associated with fruity and floral notes, were positively correlated to L. paracollinoides, L. acidipiscis, and P. parvulus species. Although the VOCs amounts were sample-specific, overall aldehydes were mostly produced at the beginning of the fermentation, while acids, alcohols and esters at the end of the process. © 2017 Elsevier Ltd. All rights reserved. 1. Introduction Table olives are one of the most produced fermented vegetables in the Mediterranean countries. They are often found available on the market “in bulk”, stored at room temperature, without any thermal treatments (Panagou et al., 2013), since pasteurization is often associated with olive quality deterioration (softening and loss green colour) (Dimou et al., 2013; Abriouel et al., 2014). Thus, the fermentation is the only procedure applied for table olives pres- ervation. It is usually driven by the indigenous microbiota that is strongly influenced by the olive cultivar and technological param- eters, such as temperature and salt concentration (Panagou et al., 2003; Heperkan, 2013; Lucena-Padr os et al., 2015). Overall, lactic acid bacteria (LAB) and yeasts represent a house microbiota of table olives fermentation. Nevertheless, members of Enterobacteriaceae, Staphylococcus, Pseudomonas and molds are detected at the beginning of the process, generating off-odours and off-flavours (Romeo, 2102). In addition, table olives are a suitable substrate for growth/survival of pathogens, such as Clostridium botulinum and Listeria monocytogenes. Several reports on food-borne botulism linked to consumption of conserved olives were already published (Cawthorne et al., 2005; Jalava et al., 2011). Some studies have indicated the survival, even at low concentration, of Escherichia coli O157:H7, Salmonella Enteritidis, L. monocytogenes and Bacillus * Corresponding author. E-mail address: cranda@unict.it (C.L. Randazzo). Contents lists available at ScienceDirect Food Microbiology journal homepage: www.elsevier.com/locate/fm http://dx.doi.org/10.1016/j.fm.2017.01.022 0740-0020/© 2017 Elsevier Ltd. All rights reserved. Food Microbiology 65 (2017) 136e148