Release and perception of aroma compounds during consumption

Key words: MS-Nose, in vivo aroma release, aroma perception, mouth model, artificial throat, liquid protocol, sweeteners, reversible protein-aroma interactions, emulsions, oil content, droplet size distribution, gel hardness, texture, cross-modal interactions.This thesis evaluated and validated the MS-Nose as a tool to measure aroma release during food consumption. Subsequently, the MS-Nose was used to enhance understanding of the interaction between release and perception of aroma during consumption. Cross-modal interactions, intra and interpersonal variation, and the development of a more relevant in vitro testing device (the artificial throat) were investigated.For aroma release measurements of liquids, a strict protocol was developed to reduce intra and interpersonal variation in mouth movements, breathing, and swallowing. With the use of this protocol it was shown that appropriate concentrations of both sweeteners and protein did not affect in vivo aroma release, despite their well-established effect on aroma release in static headspace and mouth model studies. Also for emulsions, the effect of oil content was smaller under in vivo conditions than under static headspace and mouth model conditions. These discrepancies indicate the necessity to perform in vivo aroma release measurements, rather than static headspace and mouth model studies to investigate the effect of food parameters on the release of aroma compounds during consumption.An artificial throat simulating the consumption of liquid foods was developed and validated as an alternative for conventional model systems, which generally focus on simulating aroma release during oral processing. The results obtained with the artificial throat correlated linearly with in vivo aroma release measurements. The aroma release and perception of a range of gels with different gel hardnesses were evaluated and a cross-modal interaction was demonstrated: An increase in gel hardness decreased the perceived aroma intensity, while the in vivo aroma release was unaffected.These findings have increased the understanding of aroma release and perception and will open the way to new approaches to modulate perceived aroma intensity

Effect of whey protein on the In Vivo Release of Aldehydes.

Retention of aldehydes by whey proteins in solutions buffered at a range of pH values was studied under static and dynamic headspace conditions and in vivo in exhaled air. Static headspace measurements showed a clear increase in retention in the presence of whey proteins for aldehydes with longer carbon chains and for buff er solutions with higher pH values. For in vivo aldehyde release measurements, these effects were much less pronounced. The presence of saliva or the binding of aldehydes to the surface of the oral cavity was not responsible for this effect. This difference can be explained by the highly dynamic conditions of in vivo aroma release of liquid products, due to the relatively large flow of air during exhalation. After swallowing, a thin film of aldehyde solution remains in the pharynx; subsequent exhalation will release both the free aldehydes present in this film and those reversibly bound to the whey protein

A protocol of measurement of In Vivo Aroma release from beverages.

The quality of in vivo aroma release measurements of beverages can be improved when a strict protocol is used to control variation in aroma release due to human factors. A trained panel was able to significantly discriminate between aqueous aroma solutions with a concentration difference as low as 17%. This protocol and headspace measurements have been applied to a lemon-lime type beverage with either bulk or lowcalorie intense sweeteners. The ingredients examined did not influence aroma release at concentrations relevant to the beverage industry. Aroma release was only affected by very high concentrations of sucrose

New device to simulate swallowing and in vivo aroma release in the throat from liquid and semiliquid food systems.

This paper describes a novel device to simulate in vivo aroma release from liquids. This artificial throat simulates the act of swallowing followed by exhalation and shows aroma release curves that are similar in shape to in vivo release profiles. Liquids are poured down a tube, and a thin liquid film remains at the inner wall of the tube. Subsequently, aroma compounds release from this film into a stream of air flowing through this tube, which is analyzed by MS-Nose analysis. The effects of air flow rate, contact time with glass surface, presence of saliva, and addition of whey protein, as well as volume, concentration, temperature, and viscosity of the liquid have been studied and compared with aroma release measurements in vivo. A high level of agreement was found. These results confirm the importance of swallowing for aroma release of liquids, as mentioned in the literature, and the usefulness of the new mimicking device

Effect of emulsion properties on release of esters under static headspace, in vivo, and artificial throat conditions in relation to sensory intensity

The effects of oil content and droplet size distributions of dilute oil-in-water emulsions on release of four esters with different hydrophobicities were studied under in vivo, static headspace, and artificial throat conditions. The effect of oil content on orthonasal and retronasal perceived intensity of ethyl hexanoate was studied using a seven-person panel. With increasing oil content and with a higher hydrophobicity of the aroma compound, a stronger decrease in aroma release was found. This effect was stronger under static headspace conditions than under in vivo and artificial throat conditions, and the sensory intensity of ethyl hexanoate was perceived stronger orthonasally than retronasally. The lowest effective oil content was determined for all systems. Of the compounds tested, droplet size distribution only influenced the in vivo release of geranyl acetate. The artificial throat results correlated well with in vivo release, giving support to the assumption that a thin layer of liquid remaining in the throat after swallowing determines aroma release