Delayed bitterness

Maier, V. P. Beverly, G. D. Limonin monolactone, the nonbitter precursor responsible for delayed bitterness in certain citrus juices. J. Food Sci., 1968, J3, A88-A92. 

Limonoids are C2(, nortriterpenoids deriving from a C30 triterpene precursor. The best known limonoids are the Azadirachta indica (neem tree) antifeedant azadirachtin (C50L C40 C6 -C60(epoxide methylene cross-link) furan) and the Citrus species (Rutaceae) bitter antifeedant limonin (G50L G40 G6 G6 C50L(epoxide)-furan). Limonin gives a delayed bitter taste to Citrus fruit. The limonoids are typically bitter compounds with insect antifeedant activity... 

Limonin (= Citrolimonin Citrus aurantium, C. limon (lemon), Bitter (delayed bitter... 

Limonin and nomilin are two bitter limonoids present in citrus juices. Systematic organoleptic tests showed that the bitterness threshold is 6 ppm (5) for limonin, and 6 ppm (6) or 3 ppm (7) for nomilin. The bitterness due to limonin develops gradually in juices after extraction from certain varieties of oranges, grapefruit, lemon, Natsudaidai, mandarin and some other minor citrus such as Iyokan and Ponkan. This phenomenon is generally referred to as "delayed bitterness". 

Limonoids are a group of chemically related triterpene derivatives found in the Rutaceae and Meliaceae families. There are two groups of limonoids the aglycones and their corresponding glucosides. A total of 36 limonoid aglycones have been isolated from Citrus and its hybrids (Table 1). Five of them are bitter in taste -limonin, nomilin, nomilinic acid, obacunoic acid and ichangin (Fig. 1). In citrus juices, limonin is the major cause of delayed bitterness. 

Liu Y, Alford AR, Rajab MS, Bentley MD (1990) Effects and modes of action of citrus limonoids against Leptinotarsa decemlineata. Physiol Entomol 15 37-45 Maier VP, Beverly GD (1968) Limonin monolactone, the nonbitter precursor responsible for delayed bitterness in certain citrus juices. J Food Sci 33 488-492 Maier VP, Grant ER (1970) Specific thin-layer chromatography assay of limonin, a citrus bitter principle. J Agric Food Chem 18 250-252... 

Saccharin. Sacchatin [81-07-2] C H NO S, which is approximately 300 times as sweet as sucrose ia coaceatratioas up to the equivaleat of a 10% sucrose solutioa, has beea used commercially as a nonnutritive sweeteaer siace before 1900, predomiaanfly ia carboaated soft drioks, tabletop sweeteaers, and dietetic foods marketed primarily to diabetics. In 1977, the FDA proposed a ban on sacchatin because of its association with bladder cancer ia laboratory animals. At the time, it was the only commercially available nonnutritive sweetener, and pubflc outcry led to a delay of the ban, which was officially withdrawn ia 1991. Instead, the FDA required that warning labels be placed on all foods that contained the iagredient. Although sacchatin is heat stable, the pubflc debate over its safety, as well as the fact that approximately one-third of the population perceives it to have a bitter aftertaste, has limited its use. 

Taste characteristics in general determine applicability of intense sweeteners. A time-intensity profile of sweetness perception similar to sucrose is desirable, and a delay in sweetness onset or a lingering sweetness are generally perceived as less pleasant. Side-tastes like bitter, liquorice or metallic taste are disadvantages which limit the applicability of some sweeteners. 

One of the approaches found most suitable to explain the sensorial properties of sweet, bitter, and sweet-bitter substances proves to be the physico-chemical approach especially as concerns hydration and surface properties (DeSimone and Fleck, 1980 Funasaki et al., 1996 Fimasaki et al., 1999 Mathlouthi and Hutteau, 1999). Thus, solution properties of sweet and bitter molecules were found informative on their type of hydration (hydrophobic or hydrophilic) and on the extent of the hydration layer (Fiutteau et al., 2003). Physico-chemical properties (intrinsic viscosity, apparent specific volume, and surface tension) and NMR relaxation rates of the aqueous solutions of sucrose, caffeine, and sucrose-caffeine mixtures were used in the interpretation of the taste modalities of these molecules and to explain the inhibition of caffeine bitterness by sucrose (Aroulmoji et al., 2001). Caffeine molecules were found to form an adsorption layer whereas sucrose induces a desorption layer at the air/water interface. The adsorption of caffeine gradually increases with concentration and is delayed when sucrose is added in the caffeine solution (Aroulmoji et al., 2004). 

History indicates that Archibald Scott Couper (1831-1892) discovered the tetravalence of carbon (and carbon-carbon bonding) simultaneously with and independently of Kekule. His publication was delayed for technical reasons by his Director Adolph Wurtz. When he was scooped by Kekule, he complained bitterly and was promptly fired by Wurtz. A physical breakdown before he was 30 effectively ended this promising scientist s career. ... 

An electronic tongue based on dnal shear horizontal surface acoustic wave (SH-SAW) devices was developed to discriminate between the basic tastes of sour, salt, bitter, and sweet [57]. Sixty MHz SH-SAW delay line sensors were fabricated and placed below a miniature PTFE housing containing the test liquid. All the tastes were correctly classified without the need for a selective biological or chemical coating. 

---