title: Comparing PTR-MS profile of milk inoculated with pure or mixed cultures of spoilage bacteria.
abstract: The volatile organic compounds (VOCs) associated with UHT milk (n=8) inoculated with either pure inoculums of Pseudomonas fluorescens (two strains tested) or Chryseobacterium sp., or with mixed cultures of 2 or all 3 of the bacterial strains, and held at 4.5 °C for up to 26 days was measured using proton transfer reaction - mass spectrometry (PTR-MS). The VOCs evolved included a range of carbonyl compounds, alcohols, esters, and acids and had significant qualitative and quantitative differences between the inoculums. Milks inoculated with paired (mixed) bacterial cultures attained patterns similar to the VOC composition of one of the pure inoculums, which could be attributed to the domination of these bacteria within the mixed inoculum. This study will help to characterize the spoilage of milk and provide important insights into understanding the factors that limit the shelf life of milk.
authors.affiliation: Department of Food Science, University of Otago, 276 Leith Walk, 9054 Dunedin, New Zealand. Electronic address: mohammad.alothman@otago.ac.nz.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Alothman
authors.affiliation: Department of Food Science, University of Otago, 276 Leith Walk, 9054 Dunedin, New Zealand. Electronic address: karen.lusk@otago.ac.nz.
authors.forename: Karen A
authors.initials: KA
authors.lastname: Lusk
authors.affiliation: Department of Food Science, University of Otago, 276 Leith Walk, 9054 Dunedin, New Zealand. Electronic address: pat.silcock@otago.ac.nz.
authors.forename: Patrick
authors.initials: P
authors.lastname: Silcock
authors.affiliation: Department of Food Science, University of Otago, 276 Leith Walk, 9054 Dunedin, New Zealand. Electronic address: phil.bremer@otago.ac.nz.
authors.forename: Phil J
authors.initials: PJ
authors.lastname: Bremer
mesh_terms: D000818:Animals; D045247:Chryseobacterium / Q000378:metabolism*; D005506:Food Contamination; D061353:Food Storage; D006358:Hot Temperature; D013058:Mass Spectrometry / Q000379:methods; D008892:Milk / Q000737:chemistry* / Q000382:microbiology*; D011522:Protons; D011551:Pseudomonas fluorescens / Q000378:metabolism*; D013997:Time Factors; D055549:Volatile Organic Compounds / Q000032:analysis*
chemical_list: D011522:Protons; D055549:Volatile Organic Compounds
keywords: Chryseobacterium; Inoculation; Microbial interaction; Milk; PTR-MS; Pseudomonas; VOC composition