Performance of two potential probiotic Lactobacillus strains from the olive microbiota as starters in the fermentation of heat shocked green olives Anthoula A. Argyri a , Aspasia A. Nisiotou a , Athanasios Mallouchos b , Efstathios Z. Panagou b , Chrysoula C. Tassou a, ⁎ a Institute of Technology of Agricultural Products, Hellenic Agricultural Organization-DEMETER, Sof. Venizelou 1, Lycovrissi, Attiki, Greece b Lab. of Microbiology and Biotechnology of Foods, Dept. of Food Science and Human Nutrition, Agricultural University of Athens, Iera Odos 75, Athens, Greece abstract article info Article history: Received 30 July 2013 Received in revised form 2 October 2013 Accepted 1 November 2013 Available online 16 November 2013 Keywords: Green olives Olive fermentation Probiotic bacteria L. plantarum L. pentosus The performance of two potential probiotic Lactobacillus strains from olive microbiota, namely L. pentosus B281 and L. plantarum B282 was assessed as starter cultures in Spanish-style fermentation of heat shocked green olives cv. Halkidiki. Two different initial salt levels were studied, 10% (w/v) and 8% (w/v) NaCl, and the brines were inoculated with (a) L. pentosus B281, (b) L. plantarum B282, and (c) a mixture of both strains. A spontaneous fermentation was also taken into account as control treatment. Prior to brining, olives were heat shocked at 80 °C for 10 min to reduce the level of the indigenous microbiota on olive drupes and facilitate the dominance of the inoculated cultures. Microbiological, physicochemical and sensory analyses were conducted throughout fermentation. The composition of LAB population and the evolution of added inocula were assessed by Pulsed Field Gel Electrophoresis (PFGE). The final population of LAB was maintained above 6 log cycles in olive flesh. Both L. pentosus B281 and L. plantarum B282 were able to dominate over indigenous LAB, albeit strain B281 exhibited higher recovery percentages (100 or 94.7% for B281 and 58.8% or 55.0% for B282 in 10% or 8% NaCl, respectively). L. pentosus B281 also dominated over L. plantarum B282, when the two strains were co- inoculated in olive fermentations. The sensory assessment showed higher preference for inoculated fermenta- tions of L. pentosus and L. plantarum separately in 8% NaCl, followed by the L. plantarum in 10% NaCl. The present study showed that probiotic strains L. pentosus B281 and L. plantarum B282, may offer a great potential for use as functional starter cultures in olive fermentation and deliver a promising probiotic food to the consumer. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Fermentation is one of the oldest food-processing/preservation technologies known to mankind which is considered as an important determining factor to control microbial growth, improve digestibility and nutritional value of food, and enhance food safety (Nout and Rombouts, 1992; Tassou et al., 2010). The most important industrial preparations are the Spanish or Sevillian style for green olives, the Californian style for black oxidized olives and the Greek style for natu- rally black olives (Sánchez Gómez et al., 2006). Spanish-style green olive fermentation is the most economically important olive processing (Aponte et al., 2012). Traditionally, this technique consists of a treat- ment with alkaline lye to hydrolyse the bitter glucoside oleuropein, followed by a washing step to remove the excess alkali. Brine is then added and a spontaneous fermentation, carried out mainly by lactic acid bacteria (LAB), takes place (Garrido Fernandez et al., 1995). However, the indigenous microbiota of the fruits varies as a function of the quality of the raw material, harvesting conditions and post- harvest treatments and may thus lead to variations in the sensory and organoleptic characteristics of the final product (Garrido Fernandez et al., 1997). Inoculation of the brine with an appropriate starter culture of LAB reduces the probability of spoilage and helps to achieve an improved and more predictable fermentation process (Panagou and Tassou, 2006). The preparation of improved commercial starter cultures specifically for table olives has been reported previously (Roig and Hernandez, 1991) with main focus on Spanish-style processing (Panagou et al., 2008). Depending on the geographical location or the olive production process, different LAB strains can be used as starter cul- tures. However, the majority of LAB preparations consist of Lactobacillus plantarum, Lactobacillus pentosus or both (Hurtado et al., 2010). Moreover, a heat shock treatment that has been used in some studies prior to the brining has been reported to improve olive fermentability without modifying the course of fermentation (Balatsouras et al., 1983; Chorianopoulos et al., 2005; Etchells et al., 1966). This has been attribut- ed to the partial eradication of the undesirable microbiota from the surface of heat shocked olives and the increased permeability of the plasma membrane of the fruit tissue cells (Balatsouras et al., 1983). Among the traditional fermented foods, table olives could be a promising probiotic food through the use of functional probiotic starter International Journal of Food Microbiology 171 (2014) 68–76 ⁎ Corresponding author. Tel.: +30 2102845940 1 2; fax: +30 2102840740. E-mail address: ctassou@nagref.gr (C.C. Tassou). 0168-1605/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.ijfoodmicro.2013.11.003 Contents lists available at ScienceDirect International Journal of Food Microbiology journal homepage: www.elsevier.com/locate/ijfoodmicro