On the role of short-chain free fatty acids for the development of a cheese-like off-note in pasteurized yoghurt

Free fatty acids (FFA) were quantified in fresh and stored, pasteurized yoghurt samples by gas chromatography without derivatization after clean-up on anion exchange SPE cartridges. After storage for 9 months the yoghurts elicited a cheese-like off-flavour, the intensity of which increased in parallel with the increase in FFA. Their generation was more pronounced at higher storage temperatures and was attributed to the activity of a heat-resistant lipase occurring in the yoghurt. Descriptive sensory experiments performed by adding FFA to fresh yoghurt demonstrated that these compounds were responsible for the off-flavour. Furthermore, odour thresholds of FFA in fresh yoghurt were determined and revealed higher thresholds of the respective compounds than their concentrations. It was, therefore, concluded that the acids produced the cheese-like flavour by synergistic sensory behaviour.