Characterization by culture-dependent and culture-independent methods of the bacterial population of suckling-lamb packaged in different atmospheres Sandra M. Osés a , Ana M. Diez a , Beatriz Melero a , Pieternel A. Luning b , Isabel Jaime a , Jordi Rovira a, * a Department of Biotechnology and Food Science, University of Burgos, Pza. Misael Bañuelos s/n, 09001 Burgos, Spain b Product Design and Quality Management Group, Department of Agrotechnology and Food Sciences, Wageningen University, P.O. Box 8129, NL-6700 EV Wageningen, The Netherlands article info Article history: Received 11 February 2013 Received in revised form 24 April 2013 Accepted 20 May 2013 Available online 28 May 2013 Keywords: Suckling lamb Shelf-life MAP qPCR PCR-DGGE abstract This study offers insight into the dynamics of bacterial populations in fresh cuts of suckling lamb under four different atmospheric conditions: air (A), and three Modified Atmosphere Packaging (MAP) envi- ronments, 15%O 2 /30%CO 2 /55%N 2 (C, commercial), 70%O 2 /30%CO 2 (O), and 15%O 2 /85%CO 2 (H) for 18 days. Microbial analyses by both conventional methods and PCR-DGGE were performed. Controversial and surprising results emerged from comparing both methods in relation to the genus Pseudomonas. Thus, conventional methods detected the presence of high numbers of Pseudomonas colonies, although PCR- DGGE only detected this genus in air-packaged samples. PCR-DGGE detected higher microbial di- versity in the control samples (A) than in the modified atmospheres (C, O, H), having atmosphere H the fewest number of species. Brochothrix thermosphacta, LAB (Carnobacterium divergens and Lactobacillus sakei), and Escherichia spp. were detected in all the atmospheres throughout storage. Moreover, previ- ously undescribed bacteria from lamb meat such as Enterobacter hormaechei, Staphylococcus equorum and Jeotgalicoccus spp. were also isolated in this study by DGGE. Additionally, qPCR analysis was used to detect and characterize strains of Escherichia coli. Virulence genes (stx 1 , stx 2 and eae) were detected throughout storage in 97% of the samples. A high CO 2 atmosphere was the most effective packaging combination doubling storage time in comparison with commercial atmosphere. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Within the EU, Spain is one of the largest producers of lamb meat (132 mil ton in 2011) with a consumption of 2.1 kg per capita in 2011 (including lamb and goat meat) (Eurostat, 2012; MARM, 2011). The consumption of suckling lamb, reared exclusively on ewe’s milk, is appreciated by consumers due to its paler and more delicate flavour (Miguélez et al., 2006; Sañudo et al., 2007). Various Protected Geographical Indications (PGI) exist in Spain that gua- rantees its quality. Since 1999, in “Castilla y León”, the EU has recognized this meat as PGI “Lechazo de Castilla y León” (Com- mission Regulation EEC No 2107/1999). It is important to highlight that suckling lamb meat is different from other red-meats (e.g. beef or elder lamb). This animal is only fed with ewe’s milk, resulting in myoglobin values of below 2 mg/g (Miguélez et al., 2008), while elder lambs have myoglobin values of around 5 mg/g (Luciano et al., 2009). Nowadays, fresh suckling lamb meat needs to be commercial- ized in smaller pieces (hind legs and forelegs) that require a longer shelf life, due to changing consumer purchase habits that involve weekly shopping trips to supermarkets and smaller family sizes. This has led to the study of different strategies to prolong shelf-life while maintaining food safety. One such strategy is to use a Modified Atmosphere Packaging (MAP) environment. However, the quality of fresh lamb meat varies according to storage conditions and atmospheric composition, which affect properties that are likely to influence its purchase, such as colour, flavour and texture (Al-Sheddy et al., 1995; Vergara and Gallego, 2001) as well as mi- crobial quality (Berruga et al., 2005; Kennedy et al., 2004). Meat products could be spoiled by different species of bacteria. Among the Gram negative bacteria Pseudomonas spp. are the dominating microflora in aerobic conditions. Moreover, many members of the family Enterobacteriaceae such as Serratia spp., Enterobacter spp. and Hafnia spp. are also easily found (Ercolini * Corresponding author. Tel.: þ34 947 258814; fax: þ34 947 258831. E-mail address: jrovira@ubu.es (J. Rovira). Contents lists available at SciVerse ScienceDirect Food Microbiology journal homepage: www.elsevier.com/locate/fm 0740-0020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.fm.2013.05.005 Food Microbiology 36 (2013) 216e222