Limonin responses

Flavones contribute to plant tissue color provided that they occur in high concentrations or are complexed with metal ions. Some flavones participate in taste for example, the highly methoxylated aglycones nobiletin, sinensetin and tangeretin are responsible for the bitter taste of citrus peel. On the other hand, some glycosylated flavones (for instance neodiosmin and rhoifolin) reduce the bitterness of some substances (limonin, naringin, caffeine, quinine) [2]. 

Fruit juices can be deacidified with a weak base anion-exchange resin. Removal of compounds which cause a bitter taste is a more popular application (26,27). It is accomplished with resins that have no ion-exchange fimctionality. In essence, they are similar to the copolymer intermediates used by resin manufacturers in the production of macroporous cation and anion exchangers. These products are called polymeric adsorbents. They are excellent for removal of limonin [1180-71-8] and naringin [1023647-2], the principal compounds responsible for bitterness in orange, lemon, and grapefruit juices. The adsorbents are regenerated with steam or alcohol. Decaffeination of coffee (qv) and tea (qv) is practiced with the same polymeric adsorbents (28). 

The amount of limonin incorporated into the juice is influenced by a number of juice processing variables. Factors such as the maceration of albedo, central vascular bundle and carpellary membranes, the time of contact between the rag and the juice, and the amount of pulp incorporated into the final juice product are known to influence juice limonin content. The uneven distribution of XIV in the various tissues of the fruit (Table VII) is largely responsible for the effects of processing variables (33). 

Chalcones and Pihydrochalcones. Chalcones and dihydro-chalcones are Intensely sweet compounds (39) that are effective in raising the threshold at which the bitterness of naringin and limonin is perceived (46). As illustrated in Figure 5, chalcones are easily formed fromTlavanone glycosides by the addition of alkali and dihydrochalcones are formed from hydrogenated chalcones. Like the flavanone neohesperidosides, the chalcones and dihydrochalcones vary in the intensity of their taste response. 

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. 

Numerous organoleptic studies have been done on bitterness as a function of limonin and/or naringin, and a myriad of additive and perhaps synergistic results have been obtained (9). Table I presents a generalized response as measured in a variety of taste studies. 

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... 

The chemical responsible for the bitter principle of lemons. It Is contained in the white spongy inner part of the rind. Too much limonin released into the juice during extraction produces bitter juice. 

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