Philippe Pollien

Comparison of nosespace, headspace, and sensory intensity ratings for the evaluation of flavor absorption by fat

The goal of this study was to better understand the correspondence between sensory perception and in-nose compound concentration. Five aroma compounds at three different concentrations increasing by factors of 4 were added to four matrixes (water, skim milk, 2.7% fat milk, and 3.8% fat milk). These were evaluated by nosespace analysis with detection by proton transfer reaction mass spectrometry (PTR-MS), using five panelists. These same panelists evaluated the perceived intensity of each compound in the matrixes at the three concentrations. PTR-MS quantification found that the percent released from an aqueous solution swallowed immediately was between 0.1 and 0.6%, depending on the compound. The nosespace and sensory results showed the expected effect of fat on release, where lipophilic compounds showed reductions in release as fat content increases. The effect is less than that observed in headspace studies. A general correlation between nosespace concentration and sensory intensity ratings was found. However, examples of perceptual masking were found where higher fat milks showed reductions in aroma compound intensity ratings, even if the nosespace concentrations were the same.

When machine tastes coffee: instrumental approach to predict the sensory profile of espresso coffee.

A robust and reproducible model was developed to predict the sensory profile of espresso coffee from instrumental headspace data. The model is derived from 11 different espresso coffees and validated using 8 additional espressos. The input of the model consists of (i) sensory profiles from a trained panel and (ii) on-line proton-transfer reaction mass spectrometry (PTR-MS) data. The experimental PTR-MS conditions were designed to simulate those for the sensory evaluation. Sixteen characteristic ion traces in the headspace were quantified by PTR-MS, requiring only 2 min of headspace measurement per espresso. The correlation is based on a knowledge-based standardization and normalization of both datasets that selectively extracts differences in the quality of samples, while reducing the impact of variations on the overall intensity of coffees. This work represents a significant progress in terms of correlation of sensory with instrumental results exemplified on coffee.

Mechanisms of Acrylamide Formation

The formation of acrylamide (AA) from L-asparagine was studied in Maillard model systems under pyrolysis conditions. While the early Maillard intermediate N-glucosylasparagine generated ∼2.4 mmol/mol AA, the Amadori compound was a less efficient precursor (0.1 mmol/mol). Reaction with α-dicarbonyls resulted in relatively low AA amounts (0.2–0.5 mmol/mol), suggesting that the Strecker aldehyde pathway is of limited relevance. Similarly, the Strecker alcohol 3-hydroxypropanamide generated low amounts of AA (0.2 mmol/mol). On the other hand, hydroxyacetone afforded more than 4 mmol/mol AA, indicating that α-hydroxycarbonyls are more efficient than α-dicarbonyls in transforming asparagine into AA. The experimental results are consistent with the reaction mechanism proposed, i.e. (i) Streckertype degradation of the Schiff base leading to azomethine ylides, followed by (ii) β-elimination of the decarboxylated Amadori compound to release AA, The functional group in β-position on both sides of the nitrogen atom is crucial. Rearrangement of the azomethine ylide to the decarboxylated Amadori compound is the key step, which is favored if the carbonyl moiety contains a hydroxyl group in β-position to the N-atom. The β-elimination step in the amino acid moiety was demonstrated by reacting under pyrolysis conditions decarboxylated model Amadori compounds obtained by synthesis.

Simultaneous distillation–extraction: preparative recovery of volatiles under mild conditions in batch or continuous operations

In a previous publication, a preparative apparatus was developed and optimized for simultaneous distillation–extraction (SDE) based on a theoretical model. In this paper, its performances were tested under various working conditions using a model mixture of flavourings. Separations were achieved at boiling water temperature as well as under mild conditions, which reduce artefact formation (room temperature, reduced pressure). High recoveries were obtained for batch experiments, but the boiler can also be fed from an external tank for continuous operations. This permits consideration of the preparative isolation of volatiles on a laboratory scale for subsequent fractionation and analysis, as well as industrial scale operations. Examples are given for real food flavours: one-step preparation and isolation of a reaction flavour, isolation of yoghurt and coffee flavourings, recovery of natural benzaldehyde from wastewater. In addition, the use of a food-grade solvent to achieve SDE isolation yields an ‘edible’ extract which can be reincorporated into a food without elimination of the solvent. Copyright

Influence of Foam Structure on the Release Kinetics of Volatiles from Espresso Coffee Prior to Consumption

The relationship between the physical structure of espresso coffee foam, called crema, and the above-the-cup aroma release was studied. Espresso coffee samples were produced using the Nespresso extraction system. The samples were extracted with water with different levels of mineral content, which resulted in liquid phases with similar volatile profiles but foams with different structure properties. The structure parameters foam volume, foam drainage, and lamella film thickness at the foam surface were quantified using computer-assisted microscopic image analysis and a digital caliper. The above-the-cup volatile concentration was measured online by using PTR-MS and headspace sampling. A correlation study was done between crema structure parameters and above-the-cup volatile concentration. In the first 2.5 min after the start of the coffee extraction, the presence of foam induced an increase of concentration of selected volatile markers, independently if the crema was of high or low stability. At times longer than 2.5 min, the aroma marker concentration depends on both the stability of the crema and the volatility of the specific aroma compounds. Mechanisms of above-the-cup volatile release involved gas bubble stability, evaporation, and diffusion. It was concluded that after the initial aroma burst (during the first 2-3 min after the beginning of extraction), for the present sample space a crema of high stability provides a stronger aroma barrier over several minutes.

Influence of in-mouth aroma release on individual perception

Abstract The relationship between individual in-mouth aroma release and individual aroma perception was investigated. Large variations in aroma release between subjects exist and the question to answer is to what extent these individual differences have an impact on aroma perception. To assess this, 13 subjects performed a 3-AFC test (three alternative forced choices), while their in-mouth aroma release simultaneously was measured by proton transfer reaction mass spectrometry (PTR-MS). In each test three solutions were consumed by the panellists, two of them were the reference at 6 ppm V, one the target at varying concentrations from 6.5 to 15 ppmV. The subjects had to identify the sample of the highest aroma concentration. A correlation between individual aroma release and aroma perception could be confirmed. Higher ability to discriminate between samples of low concentration difference was found for those subjects that showed a higher in-mouth release and a lower variability.

Prediction of the overall sensory profile of espresso coffe by on-line headspace measurement using proton transfer reaction-mass spectrometry

Abstract Analytical and sensory profiling were performed on different commercially available espresso coffees. Chemical information about differences in composition of the coffee headspace characterising different coffee blends was obtained by on-line analysis using PTR-MS. In addition, an expert panel trained for coffee tasting described each sample by scoring key flavour attributes on an 11-point intensity scale. The overall sensory description of each sample was correlated with the analytically obtained differences in chemical composition to develop a tool predicting the sensory profile based on analytical data. This novel and efficient approach of characterising the coffee aroma by on-line analysis may shorten the time required for the development of new products and improve quality control in a more automated and objective manner.

fMRI-based Neuronal Response to New Odorants in the Newborn Brain

The sense of smell is one of the oldest and the most primitive senses mammals possess, it helps to evaluate the surrounding environment. From birth, smell is an important sensory modality, highly relevant for neonatal behavioral adaptation. Even though human newborns seem to be able to perceive and react to olfactory stimuli, there is still a lack of knowledge about the ontogeny of smell and the underlying central processing involved in odor perception in newborns. Brain networks involved in chemosensory perception of odorants are well described in adults, however in newborns there is no evidence that central olfaction is functional given the largely unmyelinated neonatal central nervous system. To examine this question, we used functional magnetic resonance imaging (fMRI) in the newborn to characterize cortical response to olfactory and trigeminal odorants. Here we show that brain response to odors can be measured and localized using functional MRI in newborns. Furthermore, we found that the developing brain, only few days after birth, processes new artificial odorants in similar cortical areas than adults, including piriform cortex, orbitofrontal cortex and insula. Our work provides evidence that human olfaction at birth relies on brain functions that involve all levels of the cortical olfactory system.