Volatile organic compounds associated with milk spoilage by psychrotrophic bacteria

The volatile organic compounds of milk contaminated with psychrotrophic bacteria were studied by HS-SPME and GC/MS. Pseudomonas fluorescens PS14, Pseudomonas fragi PS55, Pseudomonas mosselii PS39, Pseudomonas rhodesiae PS62 and Serratia marcescens S92 were inoculated in sterilised milk (2.5% fat) stored at either 5 °C or 10 °C. A total of 47 volatile organic compounds (VOCs) belonging to seven chemical groups were identified in the spoiled milk. Volatile organic compound patterns peculiar to the inoculate bacterial strains were highlighted. 3-Methylbutan-1-ol, 2 methylpropan-1-ol, 3-hydroxybutan-2-one, butan-2,3-dione, butanoic and hexanoic acids were revealed as potential chemical spoilage indexes of milk spoilage due to the activity of the five psychrotrophic strains studied.