Variability between farms of New Zealand raw bovine milk flavour: Identification and characterisation of odorous outliers

Abstract Raw milk samples (n = 66, 250) were odour tested, as part of routine industrial quality control, and those few outliers with atypical odour (n = 312; 8 types) were collected from New Zealand farms between September 2017 and July 2018. For every odorous sample, a control (n = 301) was collected on the same day from the same geographical region. Solid phase micro-extraction/gas chromatography–mass spectrometry was used to conduct a targeted analysis for naturally occurring flavour-diagnostic volatile compounds. Data were analysed to characterise the outliers and to determine the potential of using chemical analysis data for milk assessments. Butyric acid and ethanol were diagnostic of many odorous samples. para-Cresol may indicate butyric acid production through mechanisms other than lipolysis. An inability to reliably predict odour classification from chemical analyses was characteristic of many samples found to contain flavour concentrations near sensory thresholds or analytical detection limits or both.