Hollowood, Tracey Ann
(2002)
Taste-Aroma-Matrix Interactions Determine Flavour Perception.
PhD thesis, University of Nottingham.
Abstract
A newly recruited sensory panel was trained in magnitude estimation and time intensity sensory techniques. Sensory analysis was combined with instrumental analysis using MS Nose to investigate the relationship between stimulus and perception using simple model food systems.
Volatile release data was collected after swallowing aqueous solutions containing a cocktail of aroma compounds. The compounds varied in their persistence during subsequent exhalations dependent on the degree of association with the mucous lining of the throat. The rate of breathing had no effect on the shape or intensity of the release profile. The data was successfully modelled using the basic principles of interfacial mass transfer. The mechanistic model included some estimated parameters for un-measurable anatomical and physiological variables, kinetic properties of the flavour compound and terms to represent the oscillatory breathing and airflow rate. Aside from the 1st exhalation, the model fitted the data very well.
The panel rated the intensity of minty flavor in a 6% gelatine gel, containing varying concentrations of carvone. The flavor was assessed using Magnitude Estimation and Time Intensity Methods. In addition, the quantity of carvone released from the gel and reaching the assessors nose was measured, breath by breath during eating, using the MS Nose. The results showed that the quantity of volatile delivered to the nose was directly proportional to the concentration in the sample, however, the absolute quantity varied greatly between individuals. Further differences were observed in the temporal dimension of their release profiles, which related to differences in their anatomy, physiology and eating habits. In some cases, these differences were mirrored by the sensory data. The relationship between perceived intensity and sample concentration was linear for both types of sensory data. Neither the speed of eating nor the concentration of volatile reached in-nose, affected an individuals ability to judge intensity. There was evidence to suggest, however, that the speed of eating affected the level of adaptation to the carvone stimulus.
The affinity of the aroma compound for water (hydrophobicity) was an important factor in influencing the temporal characteristics of the instrumental and sensory data. When aroma release was rapid (< Tmax) the sensory response occurred slightly later whereas when the aroma release was much slower (>Tmax), with intensity increasing more gradually, the sensory response preceded the instrumental data. These phenomena were explained in terms of a lag phase for neural processing when the stimulus was presented quickly and adaptation to the stimulus when it was delivered over a longer period of time.
A trained sensory panel assessed flavour and sweetness intensity in solutions containing varying concentrations of Hydroxy Propyl Methylcellulose (HPMC), sugar and flavour volatile. The flavour and sweetness of the viscous solutions were rated using magnitude estimation with a controlled modulus. In addition, the concentration of volatile released on the breath was measured using MS Nose. For low concentrations of HPMC (<0.5g/100g), perceived flavour intensity remained the same, however, a steady decrease was noted at higher concentrations (>0.6g/100g). The change in perceived intensity occurred at the point of random coil overlap (c*) for this hydrocolloid. The perceived sweetness of the solution showed a similar pattern with increasing HPMC concentration, although the inflection at c* was not so obvious. Despite the change in perceived flavour intensity, the actual concentration of volatile measured on the breath was not affected by the change in HPMC concentration. Low order polynomial models were produced to describe perceived flavour intensity and sweetness in viscous solutions containing HPMC and potential explanations for the changes in perception were discussed.
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