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Personne :
Gagnon, Mérilie

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Gagnon

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Mérilie

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Université Laval. Département des sciences des aliments

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ncf12004059

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  • PublicationAccès libre
    Effect of recycled manure solids as bedding on bulk tank milk and implications for cheese microbiological quality
    (American Dairy Science Association, 2019-10-30) Roy, Denis; Gagnon, Mérilie; Fréchette, Annie; Hamelin, Laurie; Dufour, Simon
    The dairy farm environment influences the raw milk microbiota and consequently affects milk processing. Therefore, it is crucial to investigate farm management practices such as the bedding materials. The aim of this study was to evaluate the effect of recycled manure sol-ids (RMS) as bedding material on bulk tank milk and microbiological implications for cheese quality. Bulk tank samples were collected from 84 dairy farms using RMS or straw bedding. The use of RMS did not influ-ence thermophilic and mesophilic aerobic viable counts from spores. However, straw-milk samples gave higher values for mesophilic anaerobic spore-forming bacteria (0.44 log cfu/mL) than RMS-milk samples (0.17 log cfu/mL). The presence of thermoresistant lactic acid bacteria was not increased in milk from farms using RMS. Nevertheless, taxonomic profiles of thermoresis-tant bacteria isolated were different between the 2 types of milk. More Enterococcus faecalis and Streptococcusspp. were identified in RMS-milk samples. Thermore-sistant enterococci and streptococci could easily end up in cheese. Therefore, milk proteolytic activities of these isolates were tested. Neither Streptococcus spp. nor Enterococcus faecium isolates exhibited proteolytic ac-tivities, whereas 53% of E. faecalis showed some. Also, only 1 vancomycin-resistant enterococcus was detected. Survival of selected RMS-milk samples isolates (3 E. faecalis and 1 Streptococcus thermophilus) was evalu-ated during a model Cheddar cheese manufacture. Al-though those strains survived well, they did not modify the acidification curve of milk. However, they might cause organoleptic defects during cheese maturing.
  • PublicationAccès libre
    Prevalence and abundance of lactic acid bacteria in raw milk associated with forage types in dairy cow feeding
    (Elsevier Inc., 2020-04-29) Roy, Denis; Groleau, Gisèle.; Gagnon, Mérilie; Chouinard, Yvan; Ouamba, Alexandre J. K.
    Lactic acid bacteria (LAB) found in milk can be responsible for organoleptic defects in cheese. In order to identify the source of LAB thatcouldpotentiallydevelop during cheesemaking, we evaluated theirprevalence and abundanceinmilk according to thetype of forage usedin dairy cow feeding. Foragesand bulk tank milk were sampled three times on 24farms using either hay alone (control), or grass or legume silagesupplemented or not with corn silage. Both types of silageswere either noninoculated, orinoculated with commercial preparations containing at least a Lactobacillus buchneristrainalong with Lactobacillus casei, Lactobacillus plantarum, Enterococcus faecium,or Pediococcus pentosaceus. Our resultsindicate that LAB viable counts in milksamples (2.56log cfu/mL) did not differaccording to the type of forage used. A total of 1239 LAB were isolated and identified by partial 16S rRNA gene sequencing. Although inoculation increased lactobacilli abundance in grass silage by 35%, we did not observe an effect on the LAB profile of milk. Indeed, there was no significant difference in milk LAB prevalence and abundanceaccording tothe type of forage(P >0.05). Moreover, isolates belonging to the L.buchnerigroup wererarely found in bulk tank milk (3/481isolates). Random amplified polymorphic DNA typing of 406LAB isolates revealed theplausibletransfer of some strains from silage to milk (~6%). Thus, forage is only a minor contributor to LAB contamination of milk.