Lipid breakdown and sensory analysis of milk inoculated with Chryseobacterium joostei or Pseudomonas fluorescens

The lipolytic activity, lipid oxidation, sensory effect and production of volatile compounds by Chryseobacterium joostei and Pseudomonas fluorescens in full cream milk, incubated at 4 and 25 °C, were investigated. Lipolytic activity, measured by the amount of free fatty acids released, showed high levels for both organisms. Although no significant differences between C. joostei and Ps. fluorescens were observed at 4 °C, C. joostei was significantly (P < 0.001) more lipolytic than Ps. fluorescens at 25 °C. Lipid oxidation was measured by thiobarbituric acid analysis. No significant differences between any of the inoculated milk samples were noted. During sensory analysis, C. joostei produced stronger odours than Ps. fluorescens. Different odours were also described for the two species. Volatile compound analysis determined that C. joostei has the ability to produce the same amount of off-odours during psychrotrophic and mesophilic growth conditions as Ps. fluorescens, but with different odour profiles.