Quantification of key aromatic compounds in plant-based yoghurt alternatives and dairy yoghurts produced using different starter cultures and citric acid and threonine supplements

Key aroma compounds in a large set of coconut- and soy-based yoghurt alternatives and dairy yoghurts representing a broad spectrum of aromas, flavours and their intensities were quantified using head-space solid-phase microextraction (HS-SPME) coupled with gas chromatography mass-spectroscopy (GCMS), 4-methyl-2-pentanol as an internal standard, and the method of external calibration. The importance of matrix matching of external calibration standards to samples by appropriate preparation using the same or similar milk base as well as a pH adjustment was demonstrated. Spike recovery measurements indicated satisfactory measurement accuracy. Moreover, measured concentrations were generally comparable in magnitude to those presented in the literature for similar products. Matrix matching was shown to be less critical for measurement accuracy when deuterated analogues of the aroma compounds are used as internal standards. Finally, addition of citric acid and threonine supplements before fermentation increased aromatic compound production by some starter cultures. This is a novel approach to enhancing the aromas and flavours of plant-based yoghurt alternatives or masking their off-flavours.