We evaluate products and raw materials, and technological, physical and chemical processes that lead to (un)desirable changes not only by identifying offensive odours, but also by investigating desirable material odours, such as characterising predominant smells (e.g., the smell of wood), comparing different samples both qualitatively and quantitatively, and formulating hypotheses about the formation pathways of such odorants, which are verified by studying potential precursors. We use state-of-the-art analytical methods to detect and identify such odors on a molecular basis; these procedures can be complemented by varios methods for evaluating consumer expectations of specific products, which allows for an objective assessment to be made on whether certain odour attributes are considered to be desirable or are indeed off-odors.
We have performed analyses on the odor attributes of diverse product groups and raw materials including (selected examples):
Our analytical and methodological repertoire for characterising aromas/odours in food and non-food products includes:
The characterization of individual odorants is typically achieved using high-resolution gas chromatography-olfactometry (HRGC-O) coupled to mass spectrometry (MS). The use of GC-O allows for odour-active compounds to be clearly distinguished from odourless molecules. As such, individual compounds that have an odor character resembling or relating to the off-odor can be isolated already during the analyses (cf. Fig. 1). This focussed analytical approach allows for a direct comparison between problematic samples and unaffected control samples.
Fig. 1: Chromatogram of a mineral water sample using GC-O, with examples of odour-active regions indicated by the text and arrows (© Fraunhofer IVV)
The identification of odor-active trace compounds is achieved using 2D-HR-GC-O/MS, which offers a high degree of compound separation (cf. Fig. 2). Odor compounds are thereby separated in two independent gas chromatographic columns, each housed in a separate oven that are coupled via a cryogenic trap, and are then analyzed on the basis of their mass spectrum and odour qualities as detected at an olfactory detection port by a trained sensory assessor.
We routinely align our chemo-analytical assessments with human sensory evaluations to maximise the likelihood that all of the odor-active compounds that are responsible for the off-odor of a sample are ascertained.
Fig. 2: Schematic of 2D-HRGC-MS/O systems (© Fraunhofer IVV)
Often, even minute traces of highly odoros substances can alter the flavor of a food. Combining analytical and olfactory assessment methods offers a highly accurate and directed analysis of odor-active compounds at trace concentrations. This has enabled us, for example, to identify the key compounds responsible for a plastic-like off-flavor, or similarly a medicinal off-flavor, in mineral water samples.