Odor optimization of raw materials and articles of everyday use

Odor characterization and optimization

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.


Products and raw materials

We have performed analyses on the odor attributes of diverse product groups and raw materials including (selected examples):

  • dyes, pigments, paints, inks
  • solvent and base formulations
  • plasticisers, lubricants, UV stabilisers
  • adhesives, binders
  • cleaning agents
  • cosmetics and body care products, as well as their associated raw materials
  • plastics, polymers, recyclates
  • wood, paper and cardboard products, cellulose-based materials
  • textiles, clothing materials, leather products, functional materials
  • articles of daily use, toys
  • furniture and furnishings
  • raw materials (for example, fats or fat derivatives, cellulose or cellulose derivatives)

Evaluation methods

Our analytical and methodological repertoire for characterising aromas/odours in food and non-food products includes:

  • Identification and characterisation of odorants using gas chromatography-olfactometry (GC-O), aroma extract dilution analysis (AEDA), and GC-O or 2D-GC-O coupled with mass spectrometry (2D-GC-O/MS)
  • Synthesis and comparative evaluation of reference compounds and suitable standards for quantitation, e.g., stable isotope dilution assay (SIDA) analysis
  • Comprehensive analytical characterisation of off-odours and aroma compounds using mass spectrometry, nuclear magnetic resonance (NMR), retention indices (RI), stereo-chemistry evaluations, and assessment of compounds with respect to their odour properties (odour attributes and thresholds)
  • Comprehensive structure-odour-activity relationship assessments
  • Recombinant odour trials to verify structural elucidations
  • Sensory assessments and evaluations according to standardised methods (DIN/ISO), as well as tailored sensory tests adapted to particular problems or products/product groups, specifically taking into account physiological aspects such as adaptation or partial anosmia. Sensory assessment can also be treated from a multi-sensory perspective
  • Determination of odour and taste thresholds in relation to the matrix properties of a food or raw material, as well as in relation to multi-sensory aspects. Detection, perception, and stimulation (e.g., trigeminal) thresholds of stimuli can be determined, as necessary
  • Characterization and assessment of odour release and emissions from raw materials and products, including during technological processes via on-line mass spectrometry (for example, during heat treatment, roasting, or fermentation processes; link PTR-MS)

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.

Range of services

  • Human sensory evaluation of food odors and taste, and packaging odors
    Aroma profile analysis (APA), triangle tests, hedonic evaluations

  • Combined instrumental and sensory analyses of odor-active compounds in foods and packaging
    Gas chromatography (GC) coupled with flame ionization detection (GC-FID), olfactometry (GC-O), mass spectrometry (GC-MS), or a combination of these (GC-MS/O and 2D-GC-MS/O). GC sample preparation techniques such as aroma extract dilution analysis (AEDA), Twister®, stir bar sorptive extraction (SBSE), solid-phase micro-extraction (SPME), headspace

  • Studies to identify off-odors
    Elucidation of compounds responsible for off-odor, short and long-term storage tests, precursor studies

  • Simulation of aromas and off-odors on the lab-scale

  • Isolation and purification of odorants
    Various distillation techniques such as solvent assisted flavor evaporation (SAFE) and condensation/trapping techniques

  • Quantitative determination of odorants at trace levels
    e.g. via stable isotope dilution analysis (SIDA), diverse methods for quantification, on-line detection in the gas-phase

  • Monitoring of dynamic release processes of odorants in real-time via in vivo or in vitro studies
    Proton-transfer-reaction mass spectrometry (PTR-MS) and proton-transfer-reaction time-of-flight mass spectrometry (PTR-TOFMS), with calibration using an advanced Gas Calibration Unit (GCU-a)

  • Development of concepts for optimizing desired aroma impressions and investigations into the causes of off-odors with development of avoidance strategies