Alison L. Dann

Microbial growth, communities and sensory characteristics of vacuum and modified atmosphere packaged lamb shoulders

Packaging fresh lamb in a vacuum (VAC) versus a 100% CO2 modified atmosphere (MAP) may influence product shelf-life and the bacterial communities. While VAC is a common packing method and 100% CO2 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 communities 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 log10 CFU/cm(2) for VAC lamb and 4-6 log10 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.

Effect of abattoir and cut on variations in microbial communities of vacuum-packaged beef

This report builds on the earlier studies of the shelf-life of chilled Australian vacuum packaged (VP) beef primals (striploin and cube roll), products distinguished in the global marketplace for unusually long shelf-life. Notable findings in those studies were a shelf-life of at least 26weeks at -0.5°C, low microbial counts, and relatively high sensory scores. However, growth rates for total viable counts (TVC) and lactic acid bacteria (LAB) varied among the different abattoirs. The present study adds to these findings, by providing greater definition about temporal changes in bacterial communities using terminal restriction fragment length polymorphism (TRFLP) and clone library analyses of 16S ribosomal RNA (16S rRNA) gene, and measuring statistical associations among abattoir, beef cut, storage time and sensory attributes. Bacterial communities changed over time, with Carnobacterium spp. typically predominating (29-97%) at the end of storage. Variation in TRFLP profiles showed that different Carnobacterium strains predominated in different abattoirs, and that additional variation was due to the presence of other taxa typical of VP meat microbiomes. TRFLP-based community structure correlated significantly (P≤0.01) with sensorial characteristics, such as vacuum integrity, confinement odour, and intact pack appearance of beef. This study shows that Carnobacterium spp. predominate on extended shelf-life VP beef primals, while other taxa may produce subtle effects on shelf-life duration.

Occurrence of viruses within Tasmanian vegetable crops and identification of a novel Polerovirus infecting pea

Tasmanian vegetable crops (broccoli, carrots, cauliflower, common bean, and pea) were tested for virus infection with Potyviruses (all crops), members of the Luteoviridae (all except carrot), Alfalfa mosaic virus (all except brassicas), Cucumber mosaic virus (all except carrot and cauliflower), Subterranean clover stunt virus (legumes only), Tomato spotted wilt virus (legumes only) and Cauliflower mosaic virus (brassicas only) over three seasons (2007–2010). Low (and sporadic) incidence of each virus (or virus group) was found in pea crops. Only Luteovirid and SCSV infections were found in bean crops at low frequency and incidence. Virus infection was not detected in carrot crops. Broccoli crops recorded generally low incidence of all four viruses or groups tested for, whilst cabbage crops recorded very low incidence of CaMV only. In the pea and broccoli crops members of the Luteoviridae were the most prevalent viruses detected. Samples that tested positive for generic Potyvirus and Luteoviridae tests were retested using virus specific antiserum and/or RT-PCR. Potyvirus detections (from pea crops in the first year of testing) were due to infection with Pea seed-borne mosaic virus (PSbMV). These samples were all sourced from a single imported seed line. Subsequent testing over the next two seasons failed to show evidence of PSbMV which may have been eliminated with destruction of the seed source. Molecular analyses of a selection of Luteovirid isolates revealed most infections were due to Turnip yellows virus with five isolates from pea belonging to a putative novel Polerovirus species with closest homology to Cucurbit aphid-borne yellows virus.