MS-nose flavour release profile mimic using an olfactometer

W.L.P. Bredie and M.A. Petersen (Editors) Flavour Science: Recent Advances and Trends 9 2006 Elsevier B.V. All rights reserved.

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MS-nose flavour release profile mimic using an olfactometer Peter M.T. de Kok, Alexandra E.M. Boelrijk, Catrienus de Jong, Maurits J.M. Burgering and Marc A. Jacobs

NIZO food research, Flavour Division, P.O. Box 20, 6710 BA Ede, The Netherlands

ABSTRACT An olfactometer has been 'trained' to produce flavour release curves imitating profiles of authentic foods as measured with an MS-Nose. These sensory cues have been used to verify the effect of combining food reformulations (matrix effects) with flavour release profiles of the non-modified food. Cross-modal interactions have been proven important factors to take into account while optimising flavour intensity and quality. Understanding and tailoring the olfactometer has been proven essential in order to be able to produce reliable and accurate controlled aroma release profiles using the olfactometer. 1. I N T R O D U C T I O N A decade ago, flavour quality and flavour performance in foodstuffs were largely seen in the context of knowing the exact composition of flavour systems. Many studies focused on establishing the aroma compositions using state-of-the-art analytical methods. With the introduction of e.g. the AEDA [1] and Charm [2] methods, establishing the (relative) importance of compounds to the overall sensory impression became feasible. However, especially with the increasing consumer demand for reduced fat levels in foods, it became evident that not only flavour composition, but also flavour release is an important factor to take into account. MS-Nose technology provided a unique tool to measure in vivo flavour release profiles. These detailed release curves enabled the development of mathematical models to describe and predict release behaviour in foods [3]. Based on many studies in the field [4], understanding the parameters that affect release did increase rapidly. Liquid layer formation in the throat after swallowing proved important [5] and tools were developed to simulate and measure the effects [6].

586 Although detailed and predictive flavour release models have been developed and are available, manipulating and adapting flavour release profiles have proven difficult. As release is largely determined by the food matrix properties, experimentally verifying release profiles, and the effects variations thereof exhibit, is still lacking. Recently, Hort et al. [7] used a multi-channel flavour delivery system with time intensity measurement techniques while Hummel et al. have applied olfactometry in many studies (e.g. [8]). Using a Burghart OM4 olfactometer, odour profiles were generated closely mimicking release curves as measured using APCI-MS nose space analysis (MS-Nose). This has enabled the simulation of sensory experiences from modified foods with authentic aroma release profiles and/or (over-)compensating for food matrix effects. 2. M A T E R I A L AND M E T H O D S

For this study, in vivo and simulated release profiles were measured using an APCI-MS spectrometer (MS-nose). The in vivo release was determined for ethyl butyrate in strawberry flavoured whole milk and skim-milk. The in vivo measurements were performed using a standard protocol for swallowing and breathing [9].

Figure 1. Burghart OM4 olfactometer. For simulation of the in vivo release profiles, a Burghart OM4 four channel mono-rhinal olfactometer was used, as shown in Figure 1. The olfactometer was filled with a 60 ml solution of 10 ppm ethyl butyrate in polyethylene glycol. The sum of the dilution and flavoured flows was kept constant at 7.5 1/min and the exhaust flow was set at 8 1/min. During the release simulation the flavoured flow varied in the range 0.2-1.3 1/min for the whole milk simulation and 0.9-5.9 1/min for the skim-milk profile. Pulses duration the simulation were set at 600 ms, whereas the timing between pulses was varied according to the in vivo profile to be simulated. The generated odour concentrations were measured using the MS-Nose. 3. RESULTS After swallowing a strawberry flavoured milk sample, a broad range of flavour components is released into the air stream from the throat to the nose space. From this

587 range of components, ethyl butyrate, a sweet candy-like flavour, was selected as the model component for simulating of the release profile using the olfactometer. Hence strawberry flavoured milk- and skim milk samples were used to generate the MS-Nose time-intensity curves (not shown) for ethyl butyrate. Both samples did contain 18 ppm ethyl butyrate. Simulating the MS-Nose time-intensity curves of a particular arbitrary subject, the release profiles of skim-milk and whole milk generated with the olfactometer are shown in Figures 2a and c, respectively. The inhalation/exhalation cycles are clearly represented by peaks in the simulation. The profile for skim-milk shows high initial concentrations, which subsequently rapidly decline. skim

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Figure 2. Olfactometer simulation of release profiles. (a) and (c) APCI-MS spectrometry (MSNose) chromatograms of ethyl butyrate release in skim milk and whole milk, respectively. (b) and (d) Comparison of relative peak areas (MS-Nose) for in vivo release and integrated olfactometer generated profile. In the case of whole milk, containing 3% fat, the maximum concentrations in the release profile are substantially lower, due to partitioning of the hydrophilic flavour into the dispersed fat phase. As one would expect, the partitioning of the flavour results in a higher persistence of the release, as the fat phase acts as a flavour reservoir. Figures 2b and d compare the integrated relative peak areas in MS-Nose recorded release profiles with the integrated peak areas as were obtained using the olfactometer,

588 the latter simulating the release profiles from the MS-Nose. After careful configuration, only a single significant difference between the MS-Nose target and the olfactometerproduced load was observed for low fat skim-milk 10 seconds after the first exhalation response (second peak). In this particular instant, the olfactometer was set to generate very high flows through the flavour solution in order to simulate the maximum intense flavour release of a the lipophilic compound from a low fat system. For all lower stimuli, such as in the case of whole milk, the peak areas generated closely matched the ones obtained from the in vivo measurements. 4. C O N C L U S I O N To tailor release profiles, insight in the physics of an olfactometer and its implementation is essential. Additionally, an MS-nose is required to measure target in vivo release curves and for calibration of the instrument. Timings, solvent effects and dilutions of the flavours are important parameters to operate this system in order to successfully mimic release curves. Once experimental/operational parameters have been established, controlled aroma delivery is feasible. Early experiments have shown that cross-modal interactions (e.g. texture and orthonasal; aroma delivery) are significant. In order to minimise sensory effects while modifying textures, aroma delivery systems require extra corrections relative to unaltered transferring delivery profiles from the authentic foodstuff (not reported here). References

1. 2. 3. 4. 5. 6. 7. 8. 9.

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