Search

The potential adulteration of kid or lamb rennet with calf rennet is of interest for some Protected Designation of Origin cheeses producers and those looking for a specific cheese typicality. The approach proposed here for the authentication of kid or lamb rennet is based on the immuno-detection of bovine pepsin possibly present in calf rennet in varying quantities. The developed immunoassay (indirect ELISA) used a monoclonal antibody (mAb) raised against bovine pepsin. This mAb was found to be specific as it didn't cross-react with the pepsin of animal species other than bovine (kid, lamb, pig) and with other milk-clotting enzymes (chymosin and microbial enzymes). Adulteration tests were conducted with kid and lamb rennets spiked with a wide range of calf rennet (from 0 to 100% v/v). The presence of bovine pepsin was detected at low levels down to 6 mg/L in kid and lamb rennets. Good linear relationships were obtained between added bovine pepsin concentration and the absorbance values over the range 1.25–120 mg/L. Results showed that indirect ELISA proved to be an interesting tool for testing rennets authenticity targeting bovine pepsin as an indicator of the bovine adulteration of kid and lamb rennets.

6 graph.; Pepsin and chymosin are milk-clotting enzymes found in rennets. They differ in their pH and temperature sensitivities and their milk-clotting activity (MCA)/proteolytic activity ratio which impact cheese technology. Therefore, characterization of rennet should not be limited to its total MCA, but also its enzymatic composition. Monoclonal antibodies against pepsin, obtained from mice immunized with purified pepsin, were characterized. A specific inhibition enzyme-linked immunosorbent assay (ELISA) was developed for the quantification of pepsin in rennets. The limit of quantification was 143 ng pepsin/ mL. The precision within runs ranged from 7.0 to 9.4%, for rennets with low and high pepsin concentrations, respectively. The precision among runs also ranged from 8.8 to 11.4%. Satisfying recovery, from 84.7 to 100.3%, was found with spiked samples. The applicability of the developed inhibition ELISA for pepsin quantification was assessed by analyzing commercial rennets, and compared to the standard chromatographic method 110A of International Dairy Federation. The relation and agreement between methods were evaluated using Deming regression analysis and Bland-Altman plot. A good agreement was found with a fixed bias. By means of bias subtraction, inhibition ELISA could be a reliable alternative for rapid and sensitive determination of pepsin in rennet.

International audience; Poplar crates are widely used in contact with foodstuffs. One of the major markets for poplar crates is apple packaging. As a direct food contact material, wood is subject to European regulation no 1935/2004, which requires no negative effect of material or packaging on foodstuffs. This study aims to quantify the transfer of Penicillium expansum conidia and Escherichia coli from poplar specimens to Golden apples. This [microorganisms-poplar-Golden apple] model was developed taking into account realistic parameters with extreme and usual conditions. Poplar specimens were artificially contaminated with P. expansum and E. coli. They were then put in contact with apples and stored in a climatic room for up to one week. Both wood specimens and apples were analyzed to assess the survival of microorganisms on wood specimens and the proportion of microorganism transfer to apples. Whereas P. expansum conidia survived but did not grow on wood specimens, E. coli mortality was observed after one hour of contact with wood. The proportion of both microorganisms transferred to apples was less than 0.25%. The impact of wood moisture content, contact time between wood and apples, and apple supply variability on the transfer levels were studied. The hygroscopic properties of wood were discussed. The low and reproducible transfer levels observed demonstrate that poplar is a safe packaging material for apples.

International audience; In recent years, foodborne viruses, especially human noroviruses (NoV) and hepatitis A virus (HAV), have been increasingly reported as the causes of foodborne disease outbreaks. Soft red fruits, especially raspberries, have a high incidence among the types of food concerned. Due to low infectious doses and low concentrations of enteric viruses in food samples, it is necessary to have an efficient and rapid detection method to implement prevention measures. A standard method for virus detection and quantification in food, including raspberries (XP CEN ISO/TS 15216-1 and -2,2013) is currently available. This method proposes a consensus detection approach by RT-real time PCR (RT-qPCR) but also a virus extraction procedure based on the elution-concentration principle. In this study, an alternative method of extraction in which RNAs are directly extracted from food matrices (based on direct RNA extraction) has been optimized. First, each step was improved to make it a highly rapid, specific and simple method. Second, the standard virus concentration method was compared with the optimized direct RNA extraction one. Human enteric viral surrogates, Murine Norovirus (MNV) and F-specific RNA bacteriophage GA, were selected according to their adhesion properties and resistance to pH close to our main targets (NOV and HAV). Raspberries were artificially contaminated using two different techniques (immersion and spotting) in order to define a recovery rate and the amounts of virus recovered. Results showed that the direct RNA extraction method revealed significantly higher viral extraction efficiency (46.2%) than the elution-concentration method (20.3%), with similar proportions of inhibitors for both. In the same way with inoculation by spotting, the best recovery rate of GA phage (39.7% against 0.7%) and MNV (42.8% against 0.5%) was observed by direct RNA extraction. For the lowest concentrations of phage and virus in the immersion bath, only the direct RNA extraction method allowed their recovery. Direct RNA extraction proved to be more effective (best recovery rate), faster (

International audience; The aim of this study was to run challenge tests to investigate the behaviour of Listeria monocytogenes in raw milk Cantal type uncooked pressed cheeses throughout the cheese process and during storage in different packagings (stretch film, vacuum packs and kraft paper) at 6 degrees C during two-thirds of the storage period, then at 10 degrees C; for kraft paper the last five days were at 15 degrees C. Whatever the weight of the cheese (10 or 40 kg), L. monocytogenes only increased during the first 24 h of cheese making and decreased significantly in both cores and rinds during ripening at 9 degrees C from day 45 to day 360. In cores, decay rate can depend on milk properties and in our experiment were associated with high levels of lactate and acetate during ripening. The decrease continued significantly in the cores during storage in all three packagings, more rapidly than during ripening. The populations of the pathogen were usually similar whatever the packaging. In rind, L monocytogenes decreased most significantly during storage in kraft paper; after 45 days of storage the counts were significantly lower in kraft paper than under vacuum whereas Gram positive non lactic acid bacteria and yeasts were at hither counts. The low a(w) (

Representative cider microorganisms (47 yeast strains and 16 bacterial strains) were studied for their ability to produce volatile phenols in a synthetic medium simulating cider conditions and supplemented with the necessary precursors. The various strains were tested for cinnamoyl esterase activity and only Lactobacillus collinoides were able to hydrolyse chlorogenic acid. Phenolic acid decarboxylase (PAD) activities were observed for 6 yeasts and 4 bacterial species allowing them to produce vinylphenols from hydroxycinnamic acids. On the other hand, 4 bacterial species exhibited phenolic acid reductase (PAR) activities leading to the formation of hydroxyphenylpropionic acids. Brettanomyces/Dekkera anomala and L. collinoides were able to produce 4-ethylcatechol (4-EC) and 4-ethylphenol (4-EP) from caffeic and p-coumaric acid, respectively, indicating that both species exhibit PAD and vinylphenol reductase (VPR) activities. In the experimental conditions used, the production of ethylphenols by L. collinoides was faster than the one observed for D. anomala.

Objective Bone marrow mesenchymal stem cells (MSC) participate in the bone marrow microenvironment by providing growth factors and matrix proteins, which play a role in the regulation of hematopoiesis, through cell-to-cell interactions. Recently, MSC have been demonstrated to improve expansion of cord blood heamtopoietic stem cells (HSC). Methods In this report, we evaluated the impact of MSC on ex vivo expansion of adult mobilized peripheral blood stem cells (PBSC). Moreover, the effect of MSC on the expanded PBSC allostimulatory capacity was also investigated, due to the well-known immunomodulatory properties of MSC. In addition, the requirement for cell-cell contact in this MSC coculture system was investigated using a transwell system. Results Our results show that MSC greatly improved the expansion rate of adult PBSC cells relative to the absolute number of 1) clonogenic cells, 2) long-term cultured cells, or 3) CD34 + cells. Whereas high levels of IL-6 on its own was sufficient to significantly improve PBSC expansion, direct contact between MSC and PBSC was required to achieve maximal expansion. Finally, MSC decreased the allostimulatory capacity of expanded PBSC. Conclusion Our data show that MSC efficiently improve expansion of adult PBSC, together with decreasing their allostimulatory capacity. Therefore, this study should provide a clinically relevant method for optimizing PBSC ex-vivo expansion, in particular when poor grafts are obtained.