Effect of Beverage Base Conditions on Flavor Release - ACS

Chapter 27

Effect of Beverage Base Conditions on Flavor Release K.

D.

Deibler and T. E. Acree

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on February 18, 2017 | http://pubs.acs.org Publication Date: September 7, 2000 | doi: 10.1021/bk-2000-0763.ch027

Department of Food Science and Technology, Cornell University, Geneva, NY 14456

Flavor released from model beverage systems in a Retronasal Aroma Simulator (RAS) was measured using solid phase microextraction (SPME) and gas chromatography mass spectrometry (GC-MS). Treatments, including temperature, air flow, percent acidity, p H , in addition to odorant, sweetener and solvent concentrations, were varied over values commonly used in commercial products. To account for interactive effects of factors, a one fourth replicate of a 2 full factorial experimental design was used to determine main effects of the beverage treatments on each odorant. Concentration, airflow, and the interaction of these two factors, affected most compounds consistently. The remaining factors affected the odorants differently. The changes in the ratio of odorants associated with specific ingredient and environmental factors are discussed in terms of their potential to modulate flavor. 9

A beverage is a complicated mixture with several ingredients that could influence the volatility of odorants. Whenever the composition of a beverage is changed, a new standard state of maximum entropy is established where new interactions result in a different enthalpy state. The high potency sweeteners commonly used in beverages such as sucralose, aspartame, and acesulfame potassium can interact directly with odorant compounds. The sweeteners and acids can affect the ionic environment of the solution modulating volatility indirectly. Solvents and other ingredients can also influence the volatility of odorant compounds both directly and indirectly. Sensory analyses have shown that the flavor of a beverage was perceptibly different when base ingredients (non-volatile components) of a beverage are changed and the same odorant ingredients used (1, 2). This is evident in many commercial products where there was an attempt to have the same flavor in two beverages with different base solutions such as diet and regular beverages. The goal of this study was to evaluate some of the ingredient and physical factors which may affect the volatility of odorants.

© 2000 American Chemical Society

Roberts and Taylor; Flavor Release ACS Symposium Series; American Chemical Society: Washington, DC, 2000.

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334 Headspace sampling from a simulated mouth system for aroma analysis is intended to capture volatiles at the concentrations that would come in contact with the olfactory epithelium (3). Due to the very low levels that the odorants are present in a beverage and subsequently in the headspace, direct headspace sampling does not produce enough analyte to be detected with most chromatographic methods, therefore, the headspace is usually concentrated on an absorbant such as with solid phase microextraction (SPME) (4-10). Under static conditions, S P M E changes the headspace concentration while it approaches equilibrium; in a dynamic situation, such as in a simulated mouth, the fiber comes to equilibrium without depleting the headspace. However, the use of an appropriately controlled standardization method to account faselectivity of S P M E coating materials is required (77).

Experimental Procedures

Stock Solution The compounds for the ethanol based stock solutions (Table I) were selected based on purity, having odor activity, existence in a beverage (e.g. coffee, citrus), and having no overlapping retention times under the chromatographic conditions used. Since so many compounds had overlapping retention times, two solutions were used to increase the number of compounds that could be evaluated. Compounds were used at levels to produce a model beverage with the odorants at concentrations commonly found in beverages (4.0 - 0.02 parts per million (ppm)).

Table I. Odorants used in stock solutions. Stock A

CAS # "~ppm in\ Stock 3-methylbutyl acetate ~ 123-92-2 ^1600 Heptanal 111-71-7 800 Ethyl valerate 539-82-2 800 Benzaldehyde 100-52-7 1600 Octanal 124-13-0 600 p-cymene 99-87-6 2000 E-ocimene 13877-91-3 800 γ-terpinene 99-85-4 2000 Nonanal 124-19-6 800 Fenchol 1632-73-1 1200 Camphor 464-49-3 400 Ethyl octanoate 106-32-1 800 Perilla aldehyde 2111-75-3 1600 Citronellyl acetate 150-84-5 800 Ethyl decanoate 110-3 8-3 800 Cinnamyl acetate 103-54-8 1200

StockB Ethyl valerate a-pinene Myrcene 1,4-cineole 1,8-cineole linalool isoborneol decanal neral E-cinnamic aldehyde geranial undecanal geranyl acteate dodecanal ethyl dodecanoate

CAS #

ppm in Stock 539-82-2 200 80-56-8 600 123- 35-3 600 470-67-7 800 470-82-6 800 78-70-6 600 124- 76-5 100 112-31-2 100 5392-40-5 500 104- 55-2 1000 141-27-5 500 112-44-7 200 105- 87-3 200 112-54-9 300 106- 33-2 500


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Justification for Sampling from RAS A solution of stock solution Β in 500 m L water was prepared. 50 m L of this solution was allowed to equilibrate for 2 hours in a 75 m L glass bottle with an i.d. of 3 cm and a teflon septum cap. The headspace was extracted for 5 minutes with a S P M E with 95 pm thick polydimethylsiloxane (PDMS) coating (Supelco, Bellefonte, PA). The remainder of the solution was placed in a retronasal aroma simulator (RAS) with the humidified air flowing over the solution (5). The "breath" leaving the R A S was sampled by S P M E exposed to the flow for 5 minutes and evaluated by gas chromatography mass spectrometry (GC-MS) multiple ion monitoring.

Test Conditions Nine factors were evaluated within the range used for beverages at minimum, maximum and midpoint values as indicated in Table II. Design-Expert® (Stat-ease, Inc., Minneapolis, M N ) was used to design an experiment that accounted for interactive effects of factors by using a one fourth replicate of a 2 full factorial experimental design consisting of 133 combinations of the factors. Flavor solution concentration was included to verify that differences could be measured under these test conditions. 9

Table II. Factors Varied in Experiment _ FACTOR Temperature (°F) A i r Flow Rate (mL/s) Concentration (relative) % Acid pH (phosphoric/citric acid) Aspartame (ppm) Acesulfame Κ (ppm) Sucralose (ppm) Ethanol (ppm)

Minimum 35 50 1 5 2.5 100 40 50 1

Maximum

""Too

150 10 10 3.5 700 250 250 10,000

Model Beverage A model beverage was prepared to a total volume of 500 m L in a volumetric flask and the stock solution was added just before beginning shearing and extracting air flow. The shearing of the R A S insured complete mixing of the stock solution in the beverage. A single unit concentration refers to a 0.1 m L of the stock solution added, while a 10 units concentration refers to a 10 fold concentration, thus 1 m L of stock solution was added to the beverage. Percent acidity and p H were controlled with phosphoric acid, citric acid and potassium citrate. A l l ingredients were food grade. The model beverage was placed in the retronasal aroma simulator (RAS) with the



336 humidified air flowing over the solution (5). The air flow leaving the R A S was sampled by S P M E exposed to the flow for 5 minutes and evaluated by gas chromatography mass spectrometry (GC-MS) multiple ion monitoring. The S P M E exposure time of 5 min was determined based on the minimum time to reach 90% absorption of the stock solution in 500 m L of water at 15 mL/s air flow rate in the R A S . When using S P M E to sample from the R A S , analyte concentration in the flow remained essentially constant due to the large sample size, continual stirring, and the short extraction time. Initially (PDMS) and carbowax/divinylbenzene coated S P M E ' s were used; however, no additional selectivity was gained using the two coatings, so P D M S 95 pm thickness was used for the entire experiment. S P M E fibers were conditioned as recommended by Supelco before use. Before each sampling, the fiber was cleaned at 225 °C for 5 minute in a G C injection port. Periodically R A S flow over 1 mL of stock in 500 m L water was extracted to monitor for coating depletion. S P M E blanks were measured to verify no artifacts were interfering with sampling. The fiber was desorbed in a G C - M S for two min at 240 °C with the injection valve closed for the initial one min. G C - M S parameters were: 0.32 mm χ 50 m OV101 column in an HP5890 gas chromatograph, constant flow, initial temperature 35 °C for 3 min, increased 4 °C/min to 150 °C, injector temperature 240 °C, detector temperature 260 °C.

Results and Discussion In order to measure the volatiles from a beverage which could potentially affect perception, volatiles liberated from a sample in a simulated mouth, a R A S , were evaluated (3). The R A S allowed for control of temperature, flow rate of air over the beverage, and stirring. The stainless steel container provided an inert environment with a relatively large sample size. Figure 1 shows a gas chromatogram of a beverage headspace sampled under static near equilibrium conditions (representing the odorants resulting from opening a bottle of beverage; Figure lb) compared to a chromatogram of the headspace from the same beverage in the dynamic conditions of a simulated mouth (RAS, representing the actual vapor phase stimulus array of aroma chemicals available when drinking the beverage; Figure la). It is noteworthy that some of the major odorants, such as decanal and geranial, became much less prominent in the R A S headspace, while other odorants like ethyl undecanoate almost vanished from the relative array of compounds. Dodecanal, which had the fifth most prominent peak among odorants from the simulated mouth sample, became the predominant volatilized chemical in the static system. On the other hand, ionone was almost non existent in the static headspace sample, but prominent from the R A S . The different ratio of the volatiles in Figure l a to l b demonstrates the importance of sampling headspaces which represent the headspace composition in the mouth. P D M S - S P M E provided sufficient selectivity and concentration power for extraction of the beverage odorants under the controlled situation of this model (77). The replicated midpoints showed a reproducibility of the sampling method and model production with a standard error range of 0.1-3%. Many statistically significant (p

Effect of Beverage Base Conditions on Flavor Release - ACS

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