RAPID AND RELIABLE IDENTIFICATION OF FOOD-BORNE YEASTS BY FOURIER-TRANSFORM INFRARED-SPECTROSCOPY

Computer-based Fourier-transform infrared spectroscopy (FT-IR) was use d to identify food-borne, predominantly fermentative yeasts. Dried yea st suspensions provided the films suitable for FT-IR measurement. Info rmative windows in the spectrum were selected and combined to achieve optimal results. A reference spectrum library was assembled, based on 332 defined yeast strains from international yeast collections and our own isolates. All strains were identified with conventional methods u sing physiological and morphological characteristics. In order to asse ss identification quality, another 722 unknown yeast isolates not incl uded in the reference spectrum library were identified both by classic al methods and by comparison of their FT-IR spectra with those of the reference spectrum library. Ninety-seven and one-half percent of these isolates were identified correctly by FT-IR. Easy handling, rapid ide ntification within 24 h when starting from a single colony, and a high differentiation capacity thus render FT-IR technology clearly superio r to other routine methods for the identification of yeasts.