Odor optimization of raw materials and articles of everyday use

We analyze everyday articles and raw materials and also technological, physical, and chemical processes that lead to undesired/desired odor changes. We identify off-odors and characterize pleasant odors, such as the odor of wood. We compare different samples, both qualitatively and quantitatively.  We identify possible reaction pathways and precursor molecules that contribute to odor formation. Advanced analytical methods enable us to detect and identify odors at a molecular level. We also are able to characterize and assess the expectations of consumers for specific products. This allows objective estimation of whether a specific product has a desired odor or an undesired off-odor. Using substantiated findings we can help you optimize the odor of your products to consumer wishes.

• Human sensory evaluation of food odors and taste, and packaging odors
  Aroma profile analysis (APA), odor transfer to food, 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), aroma extract dilution analysis (AEDA)
   

• Studies to identify off-odors
  Elucidation of compounds responsible for off-odor, forced short and long-term storage tests, modification of the manufacturing parameters, 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, Twister®, stir bar sorptive extraction (SBSE), solid-phase micro-extraction (SPME), headspace
   

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

• Monitoring of dynamic release processes of odorants in real-time
  Proton-transfer-reaction spectrometry (PTR) coupled with an time-of-flight or quadrupole mass spectrometry (PTR-TOF/Q-MS), 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

Evaluation methods for the characterization of odor in non-food products

• 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.

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)
  

Modern consumer products are made from a host of starting materials and additives. Their manufacture involves complex chemical and physical processes. When undesired product properties arise, finding the cause can be a huge challenge. In order to identify off-odors we possess start-of-the-art analytical facilities and in-depth expertise in this area. Our detailed knowledge of material properties and reaction pathways for odorous substances is utilized to discover the causes and to develop avoidance strategies. The particular focus of our research is the identification of off-odors in raw materials, other materials, and everyday consumer products and the evaluation of pleasant, desired odors in materials.
 

Reference projects

• Wood and its sensory properties
  
• Characterization and optimization of odors in plastics and recyclates
  
• Identification of irritants and off-odors in toys and children's clothing
  
• Characterization of odorous substances in adhesives