Microbial growth, communities and sensory characteristics of vacuum and modified atmosphere packaged lamb shoulders Andreas Kiermeier a , Mark Tamplin b, * , Damian May a , Geoff Holds a , Michelle Williams b , Alison Dann b a Food Safety and Innovation, South Australian Research and Development Institute, GPO Box 397, Adelaide, South Australia 5001, Australia b Food Safety Centre, Tasmanian Institute of Agriculture, University of Tasmania, Private Bag 54, Hobart, Tasmania 7005, Australia article info Article history: Received 28 February 2013 Received in revised form 1 June 2013 Accepted 28 June 2013 Available online 5 July 2013 Keywords: Shelf-life Gompertz growth model Lactic acid Terminal restriction fragment length polymorphism 454 Pyrosequencing pH abstract Packaging fresh lamb in a vacuum (VAC) versus a 100% CO 2 modified atmosphere (MAP) may influence product shelf-life and the bacterial communities. While VAC is a common packing method and 100% CO 2 MAP is used in some countries, there is little information about how these different techniques affect the growth of spoilage bacteria and sensory attributes of lamb. The aim of this study was to assess changes in microbiological and organoleptic properties, and determine differences in microbial com- munities by terminal restriction fragment length polymorphism (TRFLP) and 454 pyrosequencing, in bone-in (BI) and bone-out (BO) MAP- and VAC-packed lamb shoulders stored at 0.3  C over 12 wk. VAC and MAP lamb shoulders were acceptable in sensory test scores over 12 wk of storage at 0.3  C, despite total viable count (TVC) and lactic acid bacteria (LAB) levels increasing to 8 log 10 CFU/cm 2 for VAC lamb and 4e6 log 10 CFU/cm 2 for MAP lamb. Similar to the sensory results, there were no significant differences in microbial communities between BI and BO product. However, types of bacteria were different between VAC and MAP packaging. Specifically, while VAC shoulder became dominated by Carnobacterium spp. in the middle of the storage period, the MAP shoulder microbial population remained similar from the start until later storage times. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Most studies on vacuum (VAC)-packed meat have used beef cuts. By comparison, there is little information on the hygienic quality of sheep meat (Phillips et al., 2001). However, there are some early investigations of microbial communities on Australian and New Zealand sheep meat and in abattoirs (Gill and Penney, 1985; Phillips et al., 2006, 2001; Sumner et al., 2003; Vanderlinde et al., 1999). A recent microbiological survey on fresh sheep meat in Australian abattoirs found, in general, Total Viable Count (TVC) have shown a downward trend with counts approximately 2e 2.8 log CFU/g in the most recent survey (Phillips et al., 2013). Beef generally has a uniform surface, being largely tissue from a single muscle, and a low pH (5.5e5.8). In contrast, lamb meat tends to have a higher pH (5.6e6.8) and a heterogeneous surface, as much of the cuts are adipose rather than muscle tissue (Gill and Penney, 1985). Not much is known about the diversity of microbial community dynamics on lamb meat, as microbiological testing has depended on culture-based methods with limited ability to assess the total microbial community. In recent years, advances in molecular techniques, such as 16S rRNA gene-based terminal restriction fragment length polymorphism (TRFLP) and 454 pyrosequencing provide a culture-independent means to improve microbial com- munity analysis. TRFLP provides a generalised appraisal of the diversity of bacterial communities by assessing phylogenetic dif- ferences of fragment lengths in a given sample (Liu et al., 1997) and has been used in a variety of food such as meat (Nieminen et al., 2011) fermented beverages (Bokulich and Mills, 2012) and salmon (Powell and Tamplin, 2012). TRFLP has the advantage of been able to detect differences in a large number of samples and the data produced can be analysed using conventional multivariate statistical software. 454 Pyrosequencing can also give a phyloge- netic assessment of microbes in a complex community such as meat, for example, mince (Nieminen et al., 2011), chicken meat (Nieminen et al., 2012) and beef (Ercolini et al., 2011; Ercolini, 2013). Furthermore, combining these techniques with environ- mental and/or biochemical measurements can reveal the re- lationships between microbial community, metabolism and how this affects meat sensory perception and spoilage (Ercolini et al., 2011). * Corresponding author. Tel.: þ61 3 62266378; fax: þ61 3 62267444. E-mail address: Mark.Tamplin@utas.edu.au (M. Tamplin). 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.2013.06.016 Food Microbiology 36 (2013) 305e315