Combination of odour-stimulation tools and surface response methodology for odour recombination studies

The objective of this study was to evaluate the relative impact of 12 odour-active compounds on the odours of three different non-processed semi-hard kinds of cheese using a combination of different odour stimulation tools. Based on a previous study, eight odorants were identified as contributors to the basic odour of the cheeses, and four additional odorants were identified as contributors to the specificity of each cheese. The eight basic odorants were dispatched into four vessels of an olfactometer, which delivered mixtures following a Box-Behnken design. Each odour mixture was compared with each real cheese odour based on a direct similarity rating. An optimal basic composition of the four olfactometer vessels for each of the three cheeses was obtained. One vessel that contained a mixture of four odorants significantly impacted the odour similarity scores; thus, the four odorants (3-methyl butane-1-ol, butanoic acid, 3-methylbutanoic acid and dimethyl trisulphide) were individually tested along with four additional odorants (2,3-dimethyl pyrazine, benzaldehyde, methyl 2-methyl-3-furyl disulphide and gamma heptalactone) in a second experiment using the olfactoscan technique. A paired comparison between real cheese odours and the odour mixtures delivered by the olfactometer combined with odorants eluted from a gas-chromatograph indicated that dimethyl trisulphide primarily contributed to one of the cheese odours and butanoic acid contributed to another cheese odour. Gamma heptalactone had a positive impact, whereas benzaldehyde and 1-octen-3-one had a negative impact, on the similarity between the recombined odour and the odour of the third cheese. This original approach is a promising tool for the reformulation of food aromas

Configural perception of 6-odorant mixtures in newborn rabbits and human adults

International audienc

Rabbit neonates and human adults perceive a blending 6-component odor mixture in a comparable manner.

Young and adult mammals are constantly exposed to chemically complex stimuli. The olfactory system allows for a dual processing of relevant information from the environment either as single odorants in mixtures (elemental perception) or as mixtures of odorants as a whole (configural perception). However, it seems that human adults have certain limits in elemental perception of odor mixtures, as suggested by their inability to identify each odorant in mixtures of more than 4 components. Here, we explored some of these limits by evaluating the perception of three 6-odorant mixtures in human adults and newborn rabbits. Using free-sorting tasks in humans, we investigated the configural or elemental perception of these mixtures, or of 5-component sub-mixtures, or of the 6-odorant mixtures with modified odorants' proportion. In rabbit pups, the perception of the same mixtures was evaluated by measuring the orocephalic sucking response to the mixtures or their components after conditioning to one of these stimuli. The results revealed that one mixture, previously shown to carry the specific odor of red cordial in humans, was indeed configurally processed in humans and in rabbits while the two other 6-component mixtures were not. Moreover, in both species, such configural perception was specific not only to the 6 odorants included in the mixture but also to their respective proportion. Interestingly, rabbit neonates also responded to each odorant after conditioning to the red cordial mixture, which demonstrates their ability to perceive elements in addition to configuration in this complex mixture. Taken together, the results provide new insights related to the processing of relatively complex odor mixtures in mammals and the inter-species conservation of certain perceptual mechanisms; the results also revealed some differences in the expression of these capacities between species putatively linked to developmental and ecological constraints

Chapter 5 - Perceptual interactions in complex odor mixtures: the blending effect

absen

Human perception of the RC mixture.

<p>3D representation (2 different views) of the sensory map obtained from the free sorting task FS1 based on the sorting of the RC mixture and of its components (EA, D, V, IA, B, F) by human adults. The map was drawn using a non-metric MDS analysis. Ellipsoids represent 95% confidence intervals and were calculated using a bootstrap algorithm.</p

Rabbit perception of the RC vs. M^V and M^D mixtures.

<p>Proportions of 2 day-old rabbit pups responding in an oral activation test A) to the RC mixture, the component V of this mixture (white bar) or to another mixture of 6 components including V (M^V; grey bar), after conditioning to the odorant V (group V+; n = 16); or B) to the component D of the RC mixture (white bar) or to another mixture of 6 components including D (M^D; grey bar), after conditioning to the odorant D (group D+; n = 15).</p

Rabbit perception of the RC mixture.

<p>Proportions of 2 day-old rabbit pups responding in an oral activation test, after conditioning to one odorant of the RC mixture (IA+, EA+, D+, B+, F+ or V+), to the odorant they were conditioned to (white bars), to another unfamiliar component from RC (grey bars) and to the RC mixture (black bars) (n = 16, 19, 20, 19, 13 and 16; respectively in IA+, EA+, D+, B+, F+ and V+).</p

Elemental perception of the RC mixture by newborn rabbits.

<p>Proportions of 2 day-old rabbit pups responding in an oral activation test to the RC mixture (black bar) and to its components (white bars) after 1 conditioning to RC (RC+) or in absence of conditioning to RC (RC−) (n = 54 and 25, respectively).</p

Rabbit perception of the RC vs. RC-X mixtures.

<p>Proportions of 2 day-old rabbit pups responding in an oral activation test A) to the RC mixture deleted of one component (RC-X where X represents the removed component; grey bars) and to the component D from the RC mixture (white bar) after conditioning to the component D (results were pooled from 3 groups of pups; n = 53); or B) to the RC mixture deleted of the component D, and to the component V from the RC mixture (white bar) after conditioning to the odorant V (one group; n = 20).</p

Human perception of RC mixtures varying in component's proportions.

<p>3D representations (2 different views) of the sensory map obtained from the free sorting task FS4 based on the sorting, by human adults of the RC mixture and several mixtures formulated as RC but with varying proportions of two components (RC^{(B−, EA+)} and RC^{(V−, IA+)} (light blue), equalized proportions of odorants at 16.7% (RC^1/6, dark blue), redistributed components proportion (RC^mod; dark blue), omission of odorant V or B (RC-V and RC-B, yellow). The map was drawn using a non-metric MDS analysis. Ellipsoids represent 95% confidence intervals and were calculated using a bootstrap algorithm.</p