Viandes bovines à longue durée de conservation conditionnées sous vide : isolement et caractérisation de souches de Carnobacterium

Poster (2012, November 13)

The lactic acid bacteria Carnobacterium divergens and Carnobacterium maltaromaticum are often associated to meat and meat products and may be used as a protective culture, improving the microbial ... [more ▼]

The lactic acid bacteria Carnobacterium divergens and Carnobacterium maltaromaticum are often associated to meat and meat products and may be used as a protective culture, improving the microbial stability and the safety of these products. In this context, the aim of this study was to isolate and characterize Carnobacterium from long shelf-life vacuum-packed beef. LAB counts after culture at +22°C remained below 2.0 log UFC/cm², even at the end of shelf life. On the other hand, the ecosystem evaluation performed by metagenomics revealed the predominance of Carnobacterium and Lactobacillus on the samples. After spreading of a peptone water suspension obtained from the samples on PCA, pure isolates were collected and identified by API 50 CHL galleries. Seventy-eight % of isolates were C. maltaromaticum, 3 % C. divergens and 19 % could not be identified. The next step of this work will consist in performing a genotypic and functional characterization of these Carnobacterium isolates. [less ▲]

Effect of duration and temperature of previous vacuum-packed storage on the microbiological quality of Belgian Blue meat packed in high-oxygen atmosphere

Poster (2012, September 05)

The aim of this experiment was to study the effect of duration and temperature of previous vacuum-packed (VP) storage on the microbiological quality of Belgian Blue (BB) beef packed in high-oxygen ... [more ▼]

The aim of this experiment was to study the effect of duration and temperature of previous vacuum-packed (VP) storage on the microbiological quality of Belgian Blue (BB) beef packed in high-oxygen atmosphere. VP striploins from bulls (B) and cows (C) were stored at −1 °C and +4 °C for up to 80 days. These meats were subsequently repackaged under modified atmosphere (MA) – 70 % O2/30 % CO2 – at different times, and stored 2 d at +4 °C and 5 d at +8 °C. The average initial counts in VP meats were 3.6 log CFU/cm² (B) and 2.7 log CFU/cm² (C) for total viable count (TVC) at +22 °C; < 2.0 log CFU/cm² (B and C) for lactic ac id bacteria (LAB) at +22 °C; 1.1 log CFU/cm² (B) and 1.3 log CFU/cm² (C) for Enterobacteriaceae at +30 °C and < 1.0 log CFU/cm² (B and C) for Pseudomonas spp. and Brochothrix thermosphacta. During the first 40 days of VP storage, temperature had a striking influence on microbial growth. The maximum count differences between storage temperatures were obtained at the 20th day of storage: 2.7 log CFU/cm² (B) and 2.9 log CFU/cm² (C) for TVC, 4.0 log CFU/cm² (B and C) for LAB and 3.6 log CFU/cm² (B and C) for Enterobacteriaceae. The difference in TVC between temperatures at the 20th day tended to disappear once the meats were repacked under MA and stored during seven days. Conversely, the difference in LAB and Enterobacteriaceae counts tended to be maintained after MA repackaging, showing that duration and temperature of VP storage had influence on microbiological quality of BB meat subsequently stored in high-oxygen atmosphere. Moreover, chilling at temperatures very close to the freezing point of meat during VP storage, which has already showed innumerous advantages for physicochemical quality of meat, was capital to maintain the microbiological quality of BB fresh meat during subsequent MA-packed storage. [less ▲]

Study of the microbial diversity in vacuum-packed chilled beef from different origins through a metagenomics approach

Poster (2012, April)

Despite a diverse initial microbial population, bacterial spoilage of vacuum-packed chilled beef is mainly due to the growth of psychrotrophic bacteria. The study of the microflora of vacuum-packed ... [more ▼]

Despite a diverse initial microbial population, bacterial spoilage of vacuum-packed chilled beef is mainly due to the growth of psychrotrophic bacteria. The study of the microflora of vacuum-packed chilled beef remains a challenge since some members of the microflora may be missed or not identified by cultivation-based methods. The aim of this study was to evaluate the microbial diversity in eight batches of vacuum-packed chilled beef from different origins (Australia, Belgium, Brazil, Ireland and United Kingdom) by metagenomics. Longissimus dorsi muscle samples were homogenized and analysed in early and late stages of their shelf life by metagenomics. The metagenomic assays consisted in DNA extraction, 16S ribosomal RNA gene amplification, pyrosequencing and data analysis. All samples, except for two batches from Australia, presented a high microbial diversity in the beginning of their shelf life. Enterobacteriaceae, Pseudomonas, Burkholderia, Lactobacillus and Sterotrophomonas were some of the major bacteria identified at this stage of storage. The dominant flora (> 80 % of relative abundance) in two Australian batches was composed by Carnobacterium. At the end of the shelf life of the samples, a decrease in microbial diversity was observed in almost all batches. At this stage of storage, Carnobacterium, Lactobacillus, Lactococcus and Enterococcus were some of the major genera identified. Carnobacterium remained the dominant flora in the two Australian batches cited above, which could explain the long shelf life applicable to this meat (140 days) as some Carnobacterium strains induce a biopreservative effect especially by producing bacteriocins with a wide inhibition spectrum. Metagenomics showed to be a very useful tool to study the microbial population of a complex matrix such as meat since some of the identified genera such as Lactobacillus and Carnobacterium are known not to grow or to grow slowly in media commonly used for the isolation and cultivation of total viable counts. [less ▲]

Caractérisation des viandes bovines à très longue durée de conservation sous vide

Poster (2011, December 09)

Le but de cette étude a été d’évaluer la conservabilité de viandes bovines de différentes origines (Royaume-Uni et Irlande, Australie et Brésil) et l’influence sur celle-ci de la température de ... [more ▼]

Le but de cette étude a été d’évaluer la conservabilité de viandes bovines de différentes origines (Royaume-Uni et Irlande, Australie et Brésil) et l’influence sur celle-ci de la température de conservation (1 °C vs. +4 °C). Des paramètres physico-chimiques (pH, couleur, proportion des différentes formes redox de la myoglobine (FRMb), indice TBARS et acides organiques) et microbiologiques (flore aérobie totale, flore lactique, Enterobacteriaceae, Pseudomonas spp. et Brochothrix thermosphacta) ont été mesurés sur sept lots de contre-filet conditionnés sous vide : aux ⅔ de la DLC et à la fin de la DLC. La diversité bactérienne a été évaluée par galeries API50 CHL et par métagénomique. Le pH a diminué au cours de la conservation dans deux lots. La couleur et la proportion des FRMb sont restées stables. Une augmentation de l’indice TBARS, plus prononcée à +4 °C, a été observée. Les viandes australiennes et brésilienne ont présenté des taux en acides acétique et citrique plus élevés. Tous les lots conservés à 1 °C ont présenté une qualité microbiologique satisfaisante à la fin de leur DLC (viandes britanniques et irlandaises = 35 ~ 45 jours; australiennes = 140 jours et brésilienne = 120 jours). La conservation à +4 °C a favorisé la croissance d’entérobactéries, facteur limitant de la conservation de plusieurs lots. L’identification bactérienne a révélé la présence de bactéries connues pour leur effet bioprotecteur. La phase ultérieure de ce travail consistera à étudier la dynamique de la flore microbienne endogène en fonction des conditions environnementales appliquées (température, atmosphère). [less ▲]

Influence of temperature on conservability of chilled vacuum packed beef from different origins

Poster (2011, August 07)

The objective of this experiment was to study the conservability of chilled vacuum-packed meat depending on storage temperature (–1 °C vs. +4 °C) during the last third of their shelf life. Physicochemical ... [more ▼]

The objective of this experiment was to study the conservability of chilled vacuum-packed meat depending on storage temperature (–1 °C vs. +4 °C) during the last third of their shelf life. Physicochemical parameters (pH and colour) and microbiological growth (total aerobic bacteria, lactic acid bacteria, Enterobacteriaceae, Pseudomonas spp. and Brochothrix thermosphacta) of Longissimus dorsi samples from different origins (United Kingdom and Ireland, Australia and Brazil) were measured at: i) 2/3 of their shelf life and ii) the end of their shelf life. Sample bacteria population growing on MRS was identified by API 50 CHL strips. Unlike Irish and British samples, pH of some Australian and Brazilian samples decreased during conservation. The colour of the samples remained stable and it did not seem to be influenced by temperature. All samples conserved at –1 °C presented a satisfactory microbiological quality at the end of their shelf life (British and Irish meat = 35~45 days; Australian meat = 140 days and Brazilian meat = 120 days). On Australian and Brazilian samples, temperature did not influence total aerobic bacteria growth, but conservation at +4 °C favoured lactic acid bacteria and Enterobacteriaceae growth. API 50 CHL strip identifications revealed the presence of bacteria like Lactobacillus brevis, Carnobacterium maltaromaticum and Lactobacillus fermentum, which occur naturally in fresh meat and are known for their bioprotective effect against other microorganisms. Further analyses are being carried out using molecular methods in order to study the initial bacteria population diversity and it evolution during storage. [less ▲]

Chilling of heavy carcasses from double muscled cattle: time-temperature evolution and predictive modelling of growth of Listeria monocytogenes and Clostridium perfringens

Poster (2010, August)

The time/temperature combination during carcass chilling is of concern in order to avoid bacterial growth. The chilling speed is lower in carcasses with high muscular development such as large cattle from ... [more ▼]

The time/temperature combination during carcass chilling is of concern in order to avoid bacterial growth. The chilling speed is lower in carcasses with high muscular development such as large cattle from the Belgian Blue breed. Three slaughterhouses were selected for temperature and pH measurements during the chilling process at 6 different days on 4 half carcasses in order to obtain representative data from heavy carcasses with high muscular development. Predictive microbiology was used to evaluate the potential growth of Listeria monocytogenes and Clostridium perfringens on the surface and in the depth of the carcasses. The gamma concept was chosen as secondary model taking into account the effect of temperature, pH and water activity on the selected bacteria during the chilling process. The predicted growth potential of Listeria monocytogenes is influenced by the different environmental conditions of the selected slaughterhouses and could reach 1.4 log CFU/cm² after the chilling process. The potential growth of Clostridium perfringens is limited due to unfavourable conditions during the first hours and to low temperature later. It can be concluded that when the initial level of contaminating bacteria is not excessive the speed at which the carcass is currently chilled is sufficient to limit the growth of these two pathogens and to ensure the product quality [less ▲]

Evaluation of the endorcine disrupting chemicals contamination in the North Sea porpoise population using in vitro assays

Poster (2009)

During the last decades, the production endocrine disrupting chemicals reached such levels that they are now spread all over nature. They are known to be very slowly degraded, decreasing the environmental ... [more ▼]

During the last decades, the production endocrine disrupting chemicals reached such levels that they are now spread all over nature. They are known to be very slowly degraded, decreasing the environmental quality and posing ecological risks. Marine mammals inhabiting polluted environments accumulate high levels of these chemicals, so they can be considered good indicators of marine pollution. Thirteen major organochloride pollutants were chosen to make subject of this study: o,p’-DDD; p,p’-DDD; p,p’-DDE; o,p’-DDT; p,p’-DDT; HCB; α-HCH; β-HCH; γ-HCH; δ-HCH; PCB 138; PCB 153 and PCB 180. All these chemicals will have their endocrine disrupting effects characterized individually and collectively by report gene expression assays. The MCF7-ERE cells used in these assays were produced in the Molecular Biology and Genetic Engineering Laboratory of the University of Liège and are originated from a human mammary carcinoma. They carry a gene expressing the synthesis of luciferase and controlled by oestrogen receptors. Then, the thirteen chemicals will be searched in the blubber tissues of porpoises by the use of gas chromatography-mass spectrometry. The blubber samples will also have their endocrine disrupting effect characterized. For the moment, the estrogenic effects of the HCH isomers were put in evidence. The next steps of this work must be soon accomplished. It is expected a great level of these compounds to be found in the samples. On the other hand, their endocrine disrupting effects and how they act in agonist, antagonist and synergist ways are subject that still needs to be cleared. [less ▲]

Contamination du marsouin commun (Phocoena phocoena) de la Mer du Nord par des perturbateurs endocriniens persistants

Master's dissertation (2009)

Endocrine disrupters are molecules able to interfere with the endocrine system and are largely spread in the environment. The evaluation of the estrogenic activity of some of these substances by reporter ... [more ▼]

Endocrine disrupters are molecules able to interfere with the endocrine system and are largely spread in the environment. The evaluation of the estrogenic activity of some of these substances by reporter gene assays was the first aim of this paper. The substances chosen are also persistent organic pollutants (POP), which are capable to bioaccumulate in several organisms. Then, the occurrence of these substances was evaluated in the blubber tissue of North Sea harbour porpoises (Phocoena phocoena). Harbour porpoises are good indicators of the environmental contamination and therefore of seafood by POP. These POP were quantified by GC-MS and also by reporter gene assays. For the achievement of these aims, different analytical methods were developed. The following raking is proposed for the studied substances, according to their estrogenic activity: o,p’-DDT > o,p’-DDD > β-HCH > p,p’-DDT > p,p’-DDD > p,p’-DDE > δ-HCH > PCB 138 > γ-HCH > α-HCH > PCB 153 > HCB > PCB 180. None of them presented anti-estrogenic activity. The analysed samples presented high levels of POP, sometimes associated with estrogenic activity, confirming the occurrence of endocrine disruptors in these animals. [less ▲]

Avaliação Bacteriológica, Sensorial e Composição Centesimal de Três Formulações de Carne de Jacaré-do-Papo-Amarelo (Caiman latirostris) em Conserva

Poster (2006)

Avaliação Nutricional da Rotulagem Nutricional Obrigatória Utilizada em Salsichas Normais e Light

Poster (2004)