Sweetness and Sweeteners - American Chemical Society

Chapter 25

Downloaded by IOWA STATE UNIV on April 19, 2017 | http://pubs.acs.org Publication Date: March 4, 2008 | doi: 10.1021/bk-2008-0979.ch025

Enhancers for Sweet Taste from the World of Non-Volatiles: Polyphenols as Taste Modifiers Jakob P. Ley*, Maria Blings, Susanne Paetz, Günter Kindel, Kathrin Freiherr, Gerhard E. Krammer, and Heinz-Jürgen Bertram Flavor Research and Innovation, Symrise G m b H & Company KG, P . O . Box 1253, 37601 Holzminden, Germany *Corresponding author: [email protected], fax +49 5531 9048883

Several polyhydroxylated deoxybenzoins, benzoic acid amides and gingerdiones were synthesized and screened for their ability to enhance sweetness o f sucrose. The most active compounds tested were able to increase the sweetness of a 5 % sucrose model solution by 20 to 30 %. The compounds showed only a slight intrinsic sweetness of about 0.5 % sucrose equivalents. Simple addition of normalized sweet ratings of sucrose and test compounds resulted in ratings about 10 % lower than those determined by the panel. Some of the structures were also able to restore some of the sweetness in sugar reduced bases. As a result, the compounds can principially be used as flavor molecules to increase sweetness in selected applications and may be a good starting point to develop more active sweet taste enhancers.

400

© 2008 American Chemical Society

Weerasinghe and DuBois; Sweetness and Sweeteners ACS Symposium Series; American Chemical Society: Washington, DC, 2008.


401 Due to the increased incidence of obesity and related diseases such as diabetes type II especially in western populations, there is a high demand for food products with reduced levels of sweet and caloric carbohydrates such as sucrose and high fructose corn sirup (HFCS). On the other hand, sweetness is always a positive hedonic signal to the consumer and therefore a strong preference driver for food consumption. As a result, the products reduced in sucrose or H F C S levels should have the same sweetness impression as compared to the fall-sweetened product. For modern food development, three options offer viable solutions: the use of artificial sweeteners, the use of classical "sweet" flavors and the application of more or less tasteless sweet taste enhancers. Whereas the first two approaches are more or less state-of-the-art technology, the latter one is only rarely described in the literature (e.g. alapyraidine (/)). On the other hand the molecular basics of sweet taste reception and binding of sweet molecules seems to be clear now and a general enhancement should be possible (2, 3). Some sweeteners such as sodium cyclamate show synergistic potential in combination with sugars (4), but they have to follow the legislation for food additives and often show off-tastes (bitterness, metallic taste) and in some cases a lingering sweetness perception. In the literature, there are some hints regarding more or less tasteless sweetness modifiers: Hofmann et al described alapyraidin, a Maillard reaction product, as a sweetness enhancer (/) (alapyraidin shows in addition enhancing effects for all taste qualities (J)); lactisole, which occurs naturally in coffee beans, is a general sweet inhibitor. The modulation effects of such compounds can now indeed be explained on the molecular level (6). Alapyraidin and lactisole contain phenolic structures and therefore we decided to investigate this structural class of compounds. In addition some polyhydroxylated phenolics with isovanillic patterns show intrinsic sweetness (such as neohesperedin dihydrochalcone and analogues (7)) and with vanillic pattern bitter inhibition activities (such as homoeriodictyol (#)), which may be correlated to sweet modulating activities. Thus, we decided to screen nonvolatile polyphenols food compounds and their derivatives with a weak intrinsic aroma profile.

Experimental Syntheses Synthesis of polyhydroxylated deoxybenzoins (for structures see Figure 1) was performed via the procedures described in literature (9) starting from polyhydroxybenzene and hydroxylated phenyl acetic acid derivatives (Figure 2a).



402

17

18

19

Figure 1. Molecules evaluatedfor sweet enhancing activity.

Figure 2. Synthesis of polyhydroxylated deoxybenzoins (15, i d , 1^, short chain dehydrogingerdiones (18, 19), and polyhydroxylated benzamides (4,6 to 13).


403 Short chain dehydrogingerdiones were synthesized according to published procedures (70) starting from vanillin or isovanillin and acetoacetone (Figure 2b). Polyhydroxylated benzamides of vanillylamine were prepared by the standard condensation procedure (//) using DCCW-hydroxysuccinimide (Figure lc). A l l new compounds were purified by crystallisation or chromatography to at least 95 % and characterized by spectroscopic methods ( H - and C - N M R , HRMS, LC-MS). !

13


Sensory Evaluation For screening of sweetness enhancing activity the test compounds were directly dissolved in an aqueous 5 % sucrose solution. Panelists (healthy adults, no tasting problems known) were trained to rate sweetness intensities of different sucrose concentrations between 0 and 15 % on a structured scale of 0 (no sweetness) to 10 (very strong sweetness). A minimum of 14 testers was used for duo comparision. Mean ratings of a 5 % sucrose solution ranged between 4 and 6. For all experiments the test solutions were coded and in the case of color or cloudiness they were covered. Panelists were advised to test randomly mixed samples in the given order by the sip and spit method. The raw sensory data were analysed using the standard functions of Microsoft Excel 97. For calculation of significance Student's matched pair test was used.

Results and Discussion Sweetness of food and model applications can be influenced by volatile flavors or single flavor chemicals as well as by textural modifications (13). In such studies so called congruent flavors such as peach can increase and incongruent flavors such as lemon can decrease the perceived sweetness (14). In real applications the interactions between different taste qualities are much more important. Especially in the presence of acid a strong decrease in sweetness can be perceived. For example, the sweetness of a 8 % sucrose solution containing 0.2 % citric acid was rated 30 % lower compared to 8 % sucrose without acid; similiarly the sweetness of a 10 % sucrose/0.2 % citric acid solution against a 10 % sucrose soultion was decreased by about 20 % (own results). In our study with typical "sweet" and volatile flavor molecules such as vanillin, damascenone and diacetyl, only non-significant enhancing effects lower than 15 % (based on a 5% sucrose solution) could be found. For example vanillin at 600 ppb showed a sweetness inhibiting activity of -3 % and diacetyl at 5 ppb was able to enhance the sweetness by 8 % (non-significant). Due to the strong flavor of aroma chemicals they can not be used in a broad range of applications. A l l tested volatile "sweet" flavor molecules showed no intrinsic



404 sweetness when tested at typical flavor concentrations in pure water with closed nose. Therefore we performed a synthesis program mainly based on non-volatiles (e.g. polyhydroxylated benzoic acid benzylamides, dehydrogingerdiones, deoxybenzoins, see Figure 1) to evaluate the active structural elements responsible for the sweetness enhancing effects. In most cases the investigated molecules do not occur in nature but resembled known natural compounds. Some deoxybenzoins such as 2-(6-carboxy-2,4-dihydroxy-phenyl)-1 -(4hydroxyphenyl)-ethanone were isolated previously from white salsify (15) and short chain dehydrogingerdiones were found in ginger (9). Hydroxybenzoic acid amides are not so common in nature, but some prototypes such as anduncamide (4) were found in Piper ssp. (16) and cinnamamides such as Ncoumaroyltyramine (1) were found in several plants (17).

Sweetness Enhancement We have chosen 5 % sucrose solution as test medium because changes in sweetness could most easily be detected at this concentration. In Table I the screening results are summarized. The best sweetness enhancers were the artificial hydroxybenzamides 7, 9 and 10 and the deoxybenzoins 15 and 16. Interestingly small variations in the substitution pattern, especially by adding or "moving" methyl groups on the benzoic acid moiety or on the deoxybenzoin skeleton caused loss of activity. The exchange of vanillic patterns by isovanillic substitution (e.g. 18 compared to 19 and 7 versus 8) decreased the activity dramatically. This was somewhat surprising because the isovanillic pattern occurs in many sweet structures.

Intrinsic Sweetness To distinguish simple additive effects from synergistic activities, for the most active compounds the intrinsic sweetness was determined by comparision of the 100 ppm solution of test compound with reference solutions of sucrose (0, 0.1, 0.2, 0.3, 0.4, 0.5, 1.0, 2.0, 3.0, 4.0 and 5.0 %). The averaged sweetness (Table II) was calculated by .

,

n y x

«os Ό . 5 + H i - l + w - 2 + w2 -5 +

averaged sweetness (%) = -==

î

2

4

n -5 s

—

with: η = number of panelists and: n = number of panelists who rated χ % sucrose equivalents. x


405 Table I. Sweetness Enhancing Effects of Known and Newly Synthesized Compounds in 5 % Sucrose Solution

Compound (100 ppm)

Enhancing Activity


N-courtiaroyltyramine (I) (17) dianthramide Β (2)

a

(%) 6

Profile (100 ppm in Water) sweet

11

soapy, sweet, bitter, mouthfeel

divanillin (3) (18)

9

fatty, vanillin-like, sweet, cream

aduncatnide (4) (16)

-1

fresh, fruity, sweet, mouthfeel

homoeriodictyol (5) (8)

6

sweet, vanillin-like, phenolic, mouthfeel

6

2

vanillin-like, astringent, phenolic, dry-dusty

7

22

vanillin-like, licorice

8

0

herbal, bitter, phenolic a

9

31

10

20*

sweet, vanillin-like, licorice fruity, ester

11

4

fruity, sweet, dry-dusty

12

12

milky, sweet, vanillin-like, balsamic

13

-8

fresh, cool, sweet

14

18

sweet, metallic

15

7

cream, sweet, mouthfeel

16

16

vanillin-like, spicy, woody, balsamic, clove

17

0

sweet, dry-dusty, balsamic

18

15

neutral, drying

19

-4

dry-dusty, balsamic

(p

Sweetness and Sweeteners - American Chemical Society

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