Bitterness suppression

Both directly and indirectly, flavonoid composition affects the quality of individual citrus cultivars and hybrids. Some cultivars, such as the sour orange, are directly affected by the presence of bitter neohesperidosides to the point they are unpalatable. The quality of other cultivars may be indirectly affected due to the presence of bitterness suppressing flavone neohesperidosides. Certain hybrids, such as the K early, also contain bitter flavanone glycosides at levels which reduce its acceptability. Therefore, the knowledge of the relative type and... 

Once a purified gymnemic acid became available, much psychophysical work was done to understand the nature of the sweetness inhibition effect. The work of Bartoshuk and co-workers illustrates the course taken (15). The results of a typical experiment are shown in Figure 3. The sweetness of a sucrose solution was almost completely suppressed after holding a gymnemic acid solution in the mouth for a few seconds. Further experiments were carried out to determine the effect of gymnemic acid on the other taste qualities (sour, bitter and salty). No effect of gymnemic acid on these tastes was observed. Early work with GA extracts had produced an apparent inhibition of bitter taste, but this effect was later attributed to cross-adaptation to the taste of the crude leaf extract, which was itself quite bitter. Experiments with refined (and tasteless) extracts showed no bitterness suppression. 

Keast, R. S. J., Breslin, P. A. S. (2005). Bitterness suppression with zinc sulfate and Na-cyclamate a model of combined peripheral and central neural approaches to flavor modification. Pharmaceutical Research, 22, 1970-1977. 

Although no consistently effective chemical repellent has been developed for vertebrate pests, some promising materials have been tested as repellents that are based on predator avoidance, specifically compounds from the secretions of predators. In 1995, synthetic sulfur compounds (two thietanes, a thiolane, and a substituted methyl sulfide, which were originally identified from the anal glands of the stoat, ferret, and red fox) suppressed browsing by the introduced AustraUan bmsh-tail opossum in New Zealand about as well as FEP (83). Suggestions were made that these compounds can be made more effective by the use of bitter compounds in a cocktail. 

Gulewicz, K. and Trojanowska, K. 1995. Suppressive effect of preparations obtained from bitter lupin straw against plant pathogenic fungi. Science of Legumes, 2 141-148. 

Qing Hao is bitter, cold and aromatic, and enters the Liver and Gall Bladder meridians. It can clear and disperse heat from these meridians, especially from the blood and Yin levels. In a formula that descends the Liver-Yang, Qing Hao is used as a corrective assistant to disperse and ascend the restrained Liver-Qi, which is suppressed by the heavy and cold descending minerals and herbs. Meanwhile, since Qing Hao can brighten the eyes, clear summer-heat and damp-heat, it can be selected if red and swollen eyes with blurred vision are present in the syndrome. 

Influence of Sweeteners on Bitterness. In model system studies, natural fruit juice sugars were observed to raise the limonin threshold (24). An expanded study of natural and artificial sweeteners (26) demonstrated that sucrose, neohesperidin dihydro-chalcone (NHD), hesperetin dihydrochalcone glucoside (HDG) and aspartylphenylalanine methyl ester (AP) all raise the limonin threshold. At low sweetness levels HDG was the most effective followed by AP and NHD. Sucrose was without effect up to the 2% level. At sweetness levels equivalent to 1% sucrose, HDG, AP and NHD raised the limonin threshold in water from 1.0 ppm to 3.2, 2.5 and 1.3 ppm, respectively. Because of its high sweetness intensity, the concentration of NHD (16 ppm) was considerably lower than HDG (80 ppm) and AP (90 ppm). At 3-10% sucrose sweetness equivalency, the effectiveness of NHD increased substantially, sucrose moderately and HDG slightly, while that of AP decreased. Therefore, the sweeteners HDG, AP and NHD can effectively suppress limonin bitterness at low concentrations. 

NHD has also been found to suppress naringin bitterness (26). It was suggested as being especially useful in upgrading the flavor of low B/A, early-season grapefruit juice (27). 

Control of Juice Bitterness. A number of advances have been reported in this field since it was last reviewed (3). A commercial application of the cellulose acetate adsorption technique for the removal of limonin from citrus juices was undertaken (49). New sorbent gel forms of cellulose esters for adsorption of limonin were developed (50). Knowledge was gained that limonoids are biosynthesized in citrus leaves and translocated to the fruit (12) and that specific bioregulators can inhibit accumulation of XIV in citrus leaves (15). Additional studies were carried out on the use of neodiosmin to suppress limonin and other types of bitterness (30,51). The influence of extractor and finisher pressures on the level of limonin and naringin in grapefruit juice was reported (34). Also, further studies were conducted on the microbial sources and properties of limonoate dehydrogenase (52), the enzyme that converts XIV to XV and can be used to prevent limonin from forming in freshly expressed citrus juices (53). 

The leaves of the tropical plant Gymnema sylvestre, when chewed, suppress the ability to taste sweetness. The effect lasts for hours, and sugar seems like sand in the mouth. The ability to taste other sweeteners such as saccharin is equally suppressed. There is also a decrease in the ability to taste bitterness. The active principle of leaves has been named gymnemic acid and has been found (Stocklin et al. 1967) to consist of four components, designated as gymnemic acids, Ab A2, A3, and A4. These are D-glucuronides of acety-... 

Quinine also has pharmacological activity as an antimalarial, and some studies have been made in order to find a method to diminish or suppress its bitter taste. This can be achieved by adding sweet compounds such as sucrose or aspartame or nonspecific bitter taste inhibitors such as NaCl or phosphatidic add and tannic add [39]. The effects have been studied by sensory evaluation tests in human volunteers, a binding... 

An IPC procedure assessed recoveries of urinary catecholamines during an innovative sample clean-up [95] and was optimized to avoid interferences by anti-TB drugs [96]. Adrenergic amines were determined in a variety of bitter orange-containing dietary supplements marketed as appetite suppressants a sodium dodecyl sulfate IPR and fluorescent detection were used [97]. Similarly, two classes of compounds. 

Suzuki H, Onishi H, Hisamatsu S, et al. Acetaminophen-containing chewable tablets with suppressed bitterness and improved oral feeling. Int Pharm 2004 278(1) 57-61. 

However, insolubility in water is not always a prerequisite and in some cases water-solubilizing groups achieve as well the suppression of bitterness. Examples are A-arylan-thranilic glyceryl esters" " or lincomycin phosphate. ... 

It is also well known that sweet and bitter tastes interact. It is the case for the inhibition of sucrose sweet taste by inhibitors like lactisol or methyl-4, 6-dichloro-4,6-dideoxy-galactopyranoside which was attributed to their hydrophobic character and their bitterness (Mathlouthi et al., 1993). Bitter taste was foimd to be suppressed by sweeteners such as sucrose (Bartoshuk, 1975). The masking of unpleasant taste by pleasant (sweet) stimuli is greatly sought after in pharmaceuticals. For example, cyclodextrins were described to have the ability of masking the bitterness of drugs like propantheline... 

---