Susanne Paetz

Characterization of Flavor Modulating Effects in Complex Mixtures via High Temperature Liquid Chromatography

The identification of flavor modulating compounds, for example, bitter masking or sweet enhancing compounds, in complex mixtures such as botanical extracts or food preparations is difficult and time- and work-intensive. To accelerate this process, an improved screening method was developed on the basis of the separation of complex matrixes by the so-called LC Taste setup and subsequent comparative sensory analysis. The eluent containing only water and ethanol was diluted with a basic tastant solution (500 mg L(-1) caffeine and 5% sucrose, respectively) and evaluated by a trained panel by duo comparison tests. This novel method was applied to the known flavor and taste modulating substances homoeriodictyol (1), sterubin (2), hesperetin (3), and lactisol (9) as well as to simple mixtures of homoeriodictyol (1), sterubin (2), and hesperetin (3). To evaluate the potential of the method for more complex matrixes, the protocol was applied to plant extracts from Yerba Santa (Eriodictyon californicum) and honeybush tea (Cyclopia intermedia). The flavor modulating activities reported for homoeriodictyol (1), sterubin (2), and hesperetin (3) could be confirmed in these complex mixtures.

Structural analogues of homoeriodictyol as flavor modifiers. Part III: short chain gingerdione derivatives.

In order to find new flavor modifiers, various short chain gingerdione derivatives were synthesized as structural analogues of the known bitter masker homoeriodictyol and evaluated by a sensory panel for masking and sweetness enhancing activities. 1-(4-Hydroxy-3-methoxyphenyl)hexa-3,5-dione ([2]-gingerdione) and the homologue 1-(4-hydroxy-3-methoxyphenyl)hepta-3,5-dione ([3]-gingerdione) at concentration ranges 50-500 mg kg (-1) showed the most promising masking activity of 20-30% against bitterness of a 500 mg kg (-1) aqueous caffeine solution. Additionally, both compounds were able to reduce the bitterness of a 5 mg kg (-1) quinine solution by about 20%; however, the bitter tastes of salicine, the model peptide H-Leu-Trp-OH, and KCl solutions were not reduced. Whereas for bitter masking activity a vanillyl moiety seems to be important, some of the tested isovanillyl isomers showed an interesting sweet enhancing effect without exhibiting a significant intrinsic sweetness. The isomer 1-(3-hydroxy-4-methoxyphenyl)hexa-3,5-dione ([2]-isogingerdione) at 100 mg kg (-1) caused a significant and synergistic increase of 27% of sweet taste of a 5% sucrose solution.

Synthesis and sensory studies of umami-active scaffolds.

The class of 2‐isopropyl‐5‐methylbicyclo[4.1.0]heptane‐7‐carboxamides, 1–4, has been identified as potent umami‐tasting molecules. A scalable synthesis of this challenging scaffold and new sensory insights will be presented. Interestingly, the umami characteristics differ remarkably, depending on constitutional and stereochemical features of the parent scaffold. During our studies, we could identify the carboxamide moiety as a crucial factor to influence the umami intensity of these scaffolds. In addition, the configuration of the cyclopropyl moiety exerts some influence, whereas the absolute configuration of the menthyl scaffold, at least the tested D‐ and L‐configuration, is less important.

Evaluation of unsaturated alkanoic acid amides as maskers of epigallocatechin gallate astringency.

Some foods, beverages, and food ingredients show characteristic long-lasting aftertastes. The sweet, lingering taste of high intensity sweeteners or the astringency of tea catechins are typical examples. Epigallocatechin-3-gallate (EGCG), the most abundant catechin in green tea, causes a long-lasting astringency and bitterness. These sensations are mostly perceived as aversive and are only accepted in a few foods (e.g., tea and red wine). For the evaluation of the aftertaste of such constituents over a certain period of time, Intensity Variation Descriptive Methodology (IVDM) was used. The approach allows the measurement of different descriptors in parallel in one panel session. IVDM was evaluated concerning the inter- and intraindividual differences of panelists for bitterness and astringency of EGCG. Subsequently, the test method was used as a screening tool for the identification of potential modality-selective masking compounds. In particular, the intensity of the astringency of EGCG (750 mg kg(-1)) could be significantly lowered by 18-33% during the time course by adding the trigeminal-active compound trans-pellitorine (2E,4E-decadienoic acid N-isobutyl amide 1, 5 mg kg(-1)) without significantly affecting bitterness perception. Further, structurally related compounds were evaluated on EGCG to gain evidence for possible structure-activity relationships. A more polar derivative of 1, (2S)-2-[[(2E,4E)-deca-2,4-dienoyl]amino]propanoic acid 9, was also able to reduce the astringency of EGCG similar to trans-pellitorine but without showing the strong tingling effect.

Rubemamine and Rubescenamine, Two Naturally Occurring N-Cinnamoyl Phenethylamines with Umami-Taste-Modulating Properties

Sensory screening of a series of naturally occurring N-cinnamoyl derivatives of substituted phenethylamines revealed that rubemamine (9, from Chenopodium album) and rubescenamine (10, from Zanthoxylum rubsecens) elicit strong intrinsic umami taste in water at 50 and 10 ppm, respectively. Sensory tests in glutamate- and nucleotide-containing bases showed that the compounds influence the whole flavor profile of savory formulations. Both rubemamine (9) and rubescenamine (10) at 10-100 ppm dose-dependently positively modulated the umami taste of MSG (0.17-0.22%) up to threefold. Among the investigated amides, only rubemamine (9) and rubescenamine (10) are able to directly activate the TAS1R1-TAS1R3 umami taste receptor. Moreover, both compounds also synergistically modulated the activation of TAS1R1-TAS1R3 by MSG. Most remarkably, rubemamine (9) was able to further positively modulate the IMP-enhanced TAS1R1-TAS1R3 response to MSG ∼ 1.8-fold. Finally, armatamide (11), zanthosinamide (13), and dioxamine (14), which lack intrinsic umami taste in vivo and direct receptor response in vitro, also positively modulated receptor activation by MSG about twofold and the IMP-enhanced MSG-induced TAS1R1-TAS1R3 responses approximately by 50%. In sensory experiments, dioxamine (14) at 25 ppm in combination with 0.17% MSG exhibited a sensory equivalent to 0.37% MSG.

Investigation on Key Molecules of Huanglongbing (HLB)-Induced Orange Juice Off-flavor

Orange fruits from huanglongbing (HLB)-infected trees do not fully mature and show a severe off-flavor described as bitter-harsh, metallic, and less juicy and fruity. The investigation of juice from HLB-infected (HLBOJ) and healthy control oranges (COJ) by gas chromatography-mass spectrometry showed higher concentrations of fruity esters, such as ethyl butyrate and ethyl 2-methylbutyrate, and soapy-waxy alkanals, such as octanal and decanal, in the COJ, whereas the HLBOJ showed higher concentrations of green aldehydes such as hexanal and degradation compounds of limonene and linalool such as α-terpineol. Application of aroma extract dilution analysis on terpeneless peel oil led to the identification of long-chained aldehydes such as ( E, E)-2,4-decadienal, ( Z)-8-tetradecenal, trans-4,5-epoxy-( E)-2-decenal, ( Z)-4-decenal, and octanal with the highest flavor dilution factors among 25 odor-active volatiles in the peel oil of healthy oranges. Taste-guided fractionation and identification of the HLBOJ secondary metabolites followed by sensory validation revealed that flavanoids such as hesperidin may modulate the flavor to evoke the unacceptable harsh/metallic taste impression. Quantitation of the bitter components showed good correlation between the limonoid and flavanoid concentrations with the off-flavor and quality of the oranges obtained throughout the season.

Multiple Time–Intensity Profiling (mTIP) as an Advanced Evaluation Tool for Complex Tastants

Some foods, beverages, and food ingredients are characterized by their long-lasting aftertaste. Multiple time–intensity profiling (mTIP) was used to measure the aftertaste of compounds and mixtures over a certain period of time. Up to four different descriptors were recorded in parallel for a complex testing system, a sweetened green tea beverage. This method can also be used to evaluate possible masking effects. The bitterness and astringency of epigallocatechin gallate (EGCG) in particular was reduced by adding the “tingling” compound trans-pellitorine.