Physico-chemical characterization of natural fermentation process of Conservolea and Kalam  ata table olives and developement of a protocol for the pre-selection of fermentation starters Gianluca Bleve a, * , Maria Tufariello a , Miriana Durante a , Francesco Grieco a , Francesca Anna Ramires a , Giovanni Mita a , Maria Tasioula-Margari c , Antonio Francesco Logrieco b a Consiglio Nazionale delle Ricerche, Istituto di Scienze delle Produzioni Alimentari, Unit a Operativa di Lecce, Lecce, Italy b Consiglio Nazionale delle Ricerche, Istituto di Scienze delle Produzioni Alimentari, Bari, Italy c Department of Chemistry, Section of Food Chemistry, University of Ioannina, Ioannina, Greece article info Article history: Received 13 May 2014 Received in revised form 21 July 2014 Accepted 26 August 2014 Available online 6 September 2014 Keywords: Table olives Fermentation Microorganism selection GCeMS analysis abstract Table olives are one of the most important traditional fermented vegetables in Europe and their world consumption is constantly increasing. Conservolea and Kalam ata are the most important table olives Greek varieties. In the Greek system, the final product is obtained by spontaneous fermentations, without any chemical debittering treatment. This natural fermentation process is not predictable and strongly influenced by the physical-chemical conditions and by the presence of microorganisms contaminating the olives. Natural fermentations of Conservolea and Kalam ata cultivars black olives were studied in order to determine microbiological, biochemical and chemical evolution during the process. Following the process conditions generally used by producers, in both cultivars, yeasts were detected throughout the fermentation, whereas lactic acid bacteria (LAB) appeared in the last staged of the process. A new optimized specific protocol was developed to select autochthonous yeast and LAB isolates that can be good candidates as starters. These microorganisms were pre-selected for their ability to adapt to model brines, to have beta-glucosidase activity, not to produce biogenic amines. Chemical compounds deriving by microbiological activities and associated to the three different phases (30, 90 and 180 days) of the fermentation process were identified and were proposed as chemical descriptors to follow the fermentation progress. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction Table olives are one of the most important and popular tradi- tional fermented vegetables in Western world and in particular in Southern European countries. This product, together with olive oil, represents an important food in the Mediterranean diet. World production of table olives is estimated (2013e2014 season) in 2,574,500 tons and the 27% of this production (698,000 tons) is located in the European Union (EU) (IOOC, 2013). Spain has a leading position in table olive production with 513,100 tons, fol- lowed by Greece with 94,000 tons, by Italy with 74,000 tons and Portugal with 11,900 tons. Table olives consumption is constantly increasing throughout both EU and the world and producer countries are also the most important consumers. According to their relevance on the international markets, Kalam ata and Con- servolea are the most important table olive varieties together with Manzanilla, Sevillana and Hojiblanca and to a lesser extent Bella di Cerignola and Ascolana Tenera (Anon., 2003). Conservolea repre- sents the most economically important cultivar in Greece, corre- sponding to at least 80e85% of Greek olive production, whereas Kalam ata is the second most important cultivar used in the pro- duction of Greek table olives for domestic and foreign market (Garrido-Fernandez et al., 1997). The most important industrial preparations of table olives are the green olives by Spanish style, the black oxidized olives by Californian method and the naturally black olives by Greek style (Garrido-Fernandez et al., 1997). In the Greek system, the final product is obtained placing directly olives into brine, without any debittering pre-treatment and it is characterized by a fruity aroma and a slightly bitter taste. Today, this debittering process is carried out by spontaneous * Corresponding author. E-mail address: gianluca.bleve@ispa.cnr.it (G. Bleve). Contents lists available at ScienceDirect Food Microbiology journal homepage: www.elsevier.com/locate/fm http://dx.doi.org/10.1016/j.fm.2014.08.021 0740-0020/© 2014 Elsevier Ltd. All rights reserved. Food Microbiology 46 (2015) 368e382