Spoilage microbiota associated to the storage of raw meat in different conditions

The spoilage of raw meat is mainly due to undesired microbial development in meat during storage. The type of bacteria and their loads depend on the initial meat contamination and on the specific storage conditions that can influence the development of different spoilage-related microbial populations thus affecting the type and rate of the spoilage process. This review focuses on the composition of raw meat spoilage microbiota and the influence of storage conditions such as temperature, packaging atmosphere and use of different preservatives on the bacterial diversity developing in raw meat. In addition, the most recent tools used for the detection and identification of meat microbiota are also reviewed.     

Life Cycle Assessment (ISO 14040) Implementation in Foods of Animal and Plant Origin: Review

The importance of environmental protection has been recently upgraded due to the continuously increasing environmental pollution load. Life Cycle Assessment (LCA), wellknown as ISO 14040, has been repeatedly shown to be a useful and powerful tool for assessing the environmental performance of industrial processes, both in the European and American continents as well as in many Asian countries (such as Japan and China). To the best of our knowledge, almost no information is provided in relation to LCA implementation in Africa apart from an article related to Egypt. Although food industries are not considered to be among the most heavily polluting ones, for some like olive oil, wine, dairy, and meat processing, their impact on the environment is a heavy burden. The introduction of LCA aimed at identifying both inputs and outputs to find out which are the most detrimental to the environment in terms of water/energy consumption and solid/liquid and gas releases. In this review, a thorough coverage of literature was made in an attempt to compare the implementation of LCA to a variety of products of both plant and animal origin. It was concluded that there is a high number of subsystems suggested for the same product, thereby, occasionally leading to confusion. An idea toward solving the problem is to proceed to some sort of standardization by means of several generic case studies of LCA implementation, similarly to what had happened in the case of Hazard Analysis and Critical Control Points (HACCP) implementation in the United States, Canada, Australia, United Kingdom, and other countries.     

Effect of sulfur dioxide addition in wild yeast population dynamics and polyphenolic composition during spontaneous red wine fermentation from Vitis vinifera cultivar Agiorgitiko

The aim of the present study was to assess the effect of sulfur dioxide addition in the wild yeast population dynamics as well as the polyphenolic composition during spontaneous red wine fermentation from Vitis vinifera cultivar Agiorgitiko. The grapes were crushed and fermentation took place at 21 °C without the addition of any commercial yeast, and with and without the addition of 40 mg L^?1 SO₂. A combination of culture-dependent and culture-independent techniques was used for wild yeast population dynamics assessment and HPLC analysis for the determination of polyphenolic compounds. Regarding the former, the effect of sulfur dioxide addition was only marginal since Saccharomyces cerevisiae strains dominated the fermentation from the first day; strains belonging to Hanseniaspora spp., Lachancea thermotolerans and Metschnikowia pulcherrima species appeared only occasionally. As far as the polyphenolic content was concerned, it was enhanced with sulfur dioxide addition; however, as time progressed, the differences were reduced, suggesting that the time the juice was in contact with the skins was of greater importance than sulfur dioxide addition.     

Autoinducer-2-like activity in lactic acid bacteria isolated from minced beef packaged under modified atmospheres

Fifteen fingerprints (assigned to Leuconostoc spp., Leuconostoc mesenteroides, Weissella viridescens, Leuconostoc citreum, and Lactobacillus sakei) of 89 lactic acid bacteria (LAB) isolated from minced beef stored under modified atmospheres at various temperatures were screened for their ability to exhibit autoinducer-2 (AI-2)-like activity under certain growth conditions. Cellfree meat extracts (CFME) were collected at the same time as the LAB isolates and tested for the presence of AI-2-like molecules. All bioassays were conducted using the Vibrio harveyi BAA-1117 (sensor 1(-), sensor 2(+)) biosensor strain. The possible inhibitory effect of meat extracts on the activity of the biosensor strain was also evaluated. AI-2-like activity was observed for Leuconostoc spp. isolates, but none of the L. sakei strains produced detectable AI-2-like activity. The AI-2-like activity was evident mainly associated with the Leuconostoc sp. B 233 strain, which was the dominant isolate recovered from storage at 10 and 15°C and at the initial and middle stages of storage at chill temperatures (0 and 5°C). The tested CFME samples displayed low AI-2-like activity and inhibited AI-2 activity regardless of the indigenous bacterial populations. The LAB isolated during meat spoilage exhibited AI-2-like activity, whereas the LAB strains retrieved depended on storage time and temperature. The production of AI-2-like molecules may affect the dominance of different bacterial strains during storage. The results provide a basis for further research concerning the effect of storage temperature on the expression of genes encoding AI-2 activity and on the diversity of the ephemeral bacterial population.     

Potential of a simple HPLC-based approach for the identification of the spoilage status of minced beef stored at various temperatures and packaging systems

The shelf life of minced beef stored (i) aerobically, (ii) under modified atmosphere packaging (MAP), and (iii) under MAP with oregano essential oil (MAP/OEO) at 0, 5, 10, and 15 °C was investigated. The microbial association of meat and the temporal biochemical changes were monitored. Microbiological analyses, including total viable counts (TVC), Pseudomonas spp., Brochothrix thermosphacta, lactic acid bacteria, Enterobacteriaceae, and yeasts/moulds, were undertaken, in parallel with sensory assessment, pH measurement and HPLC analysis of the organic acid profiles. Spectral data collected by HPLC were subjected to statistical analysis, including principal component analysis (PCA) and factorial discriminant analysis (FDA). This revealed qualitative discrimination of the samples based on their spoilage status. Partial least squares regression (PLS-R) was used to evaluate quantitative predictions of TVC, Pseudomonas spp., Br. thermosphacta, lactic acid bacteria, Enterobacteriaceae, and yeasts/moulds. Overall, the HPLC analysis of organic acids, was found to be a potential method to evaluate the spoilage and microbial status of a meat sample regardless of the storage conditions. This could be a very useful tool for monitoring the quality of meat batches during transportation and storage in the meat food chain.     

Characterization of the Enterobacteriaceae community that developed during storage of minced beef under aerobic or modified atmosphere packaging conditions

The whole cell protein and macrorestriction analysis of DNA of Enterobacteriaceae isolates recovered from minced beef stored at 0, 5, 10 and 15 °C aerobically and under modified atmosphere packaging consisting of 40% CO₂-30% O₂-30% N₂ in the presence (MAP+) and absence (MAP−) of oregano essential oil were studied. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) profiles obtained from whole cell protein analysis of the Enterobacteriaceae isolates revealed seven groups. Moreover, application of a modified PFGE protocol with XbaI restriction, resulted into 19 different fingerprints. The Enterobacteriaceae community of fresh meat consisted of Serratia liquefaciens and Serratia proteamaculans. S. liquefaciens strain VK23 was the dominant isolate of Enterobacteriaceae for the most conditions adopted, except 10 °C and 15 °C under MAP + and 10 °C under MAP−. In the latter cases, Hafnia alvei represented the dominant fingerprint. Citrobacter freundii was recovered from minced beef stored aerobically, while H. alvei and Proteus vulgaris were recovered under MAP. Storage conditions affected the Enterobacteriaceae community; modified atmosphere packaging increased both species and strain diversity.     

Genotypic characterization of Brochothrix thermosphacta isolated during storage of minced pork under aerobic or modified atmosphere packaging conditions

A total of 306 colonies were isolated from the selective medium for Brochothrix spp., during the spoilage of minced pork stored at 0, 5, 10 and 15°C and packed aerobically and under modified atmosphere packaging conditions (MAP). Brochothrix biodiversity was assessed by Pulsed Field Gel Electrophoresis (PFGE), and representative strains were further analysed by Rep-PCR using primer (GTG)(5) and Sau-PCR with primers SAG(1)and SAG(2). Although, different results were obtained from the different methods, a significant diversity among isolates recovered from aerobic conditions was observed. On the contrary, isolates from MAP showed a lower degree of heterogeneity. The storage conditions affected the Brochothrix diversity, the strains isolated in the initial stage being different from the ones present at the final stage of storage at chill temperatures. A representative number of isolates, based on the results of the clustering by molecular methods, were subjected to 16S rRNA gene sequencing, revealing that all belonged to Brochothrix thermosphacta.     

Monitoring the succession of the biota grown on a selective medium for pseudomonads during storage of minced beef with molecular-based methods

In the present study, the succession of the biota grown on a selective medium for pseudomonads (pseudomonas agar based medium – PAB) during the storage of meat under different conditions was monitored. Thus, minced beef was stored aerobically and under modified atmosphere packaging in the presence (MAP+) and absence (MAP−) of oregano essential oil at 0, 5, 10 and 15 °C. A total of 267 pure cultures were recovered from PAB throughout the storage period and subjected to PCR-Denaturing gradient gel electrophoresis (PCR-DGGE) for their differentiation. In parallel, the direct analysis of the whole cultivable community (WCC) from the same medium was applied. These two approaches were used in order to indicate the lack of selectivity. Fifteen different DGGE fingerprints were obtained after PCR – DGGE analysis of the isolates, which were assigned to Pseudomonas putida (3 fingerprints), Pseudomonas fragi and Pseudomonas fluorescens, Pseudomonas spp., Serratia liquefaciens (2), Citrobacter freundii, Serratia grimesii, Hafnia alvei (3), Rahnella spp. and Morganella morganii. Twelve of them occurred during the direct analysis of the WCC. The biota succession found to be affected from the different storage conditions. However, the outcome of the two strategies was quite different, which is leading to the use of different appropriated molecular approaches in order to widen the knowledge of bacterial succession of meat.     

Microbial population dynamics during spontaneous fermentation of Asparagus officinalis L. young sprouts

The aim of the present study was to assess the spontaneous fermentation of Asparagus officinalis L. young sprouts. For this purpose, asparagus fermentation was performed according to a traditional procedure originating from northern Greece. Young asparagus sprouts were cut, submerged in a brine solution (8 % NaCl) and placed in room temperature for fermentation to occur. Fermentation was monitored by measuring pH and total titratable acidity values as well as by qualitative and quantitative assessment of the microbiota dynamics. The latter was performed by classical microbiological techniques; clustering was performed by SDS-PAGE of whole cell proteins and rep-PCR and identification by sequencing of the 16S-rRNA gene. A culture-independent approach [PCR-denaturing gradient gel electrophoresis (DGGE)] was also applied in order to obtain a more integrated view of the microbiota dynamics. Lactic acid bacteria prevailed the fermentation forming a microbial consortium that was stable at species level; Lactobacillus sakei and Enterococcus faecium dominated until the 5th day while Weissella viridescens and W. cibaria dominated from the 7th day until the end of fermentation. Combination of SDS-PAGE with rep-PCR resulted in a very efficient clustering and differentiation also at sub-species level, revealing a succession at that level of all species throughout fermentation. On the other hand, application of PCR-DGGE was of limited usefulness.     

中厚板轧机技术

奥钢联公司的中厚板轧机技术是一种全生产线的最佳技术,它包括PLATE轧制模型,与液压系统相结合的自动化系统HAGC,控制厚度的Hgdroplate软件包,最佳矩形中厚板PVR模型,控制中厚板板宽与立辊轧机相接的自动化系统(AWC) ,大型工作辊弯曲技术及控制中厚板板形和平直度的自动化系统ADCO冷却装置和中厚板冷却控制的AICOLINE模型,预平整机技术和全液压热平整控制平直度的PLANE平整模型等等,在整个工艺线路中,这些技术融合了高新技术设备和自动化集成,以提高中厚板质量,增加成材率,降低成本为最终目的.