Grapefruit bitter taste

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). 

Hagen et a/L (42) determined the relative amounts of all the flavanone glycosides in Texas grapefruit. Their results are shown in Table III. Naringin is the dominant flavonoid in grapefruit and is primarily responsible for the immediate bitter taste in grapefruit. The equally bitter poncirin and the much less bitter neohesperidin are present in relatively small amounts and do not contribute significantly to overall bitterness. 

The bitter taste in foods is not always disliked by people. There are unexpectedly many cases in which a bitter taste has a positive effect of adding richness to food such as beer, coffee, and green tea. In these cases, if the bitter taste is eliminated or replaced by other compounds, the intrinsic value of the food might be completely lost. Therefore, the bitter taste is essential for these foods. On the contrary, however, methods to eliminate the unpleasant bitterness of cheese and grapefruit have also been investigated. These efforts also contribute to the progress in research on the bitter taste.118... 

CIC The bitter taste originates from naringin. Nootkatone imparts the characteristic fresh woody odour. Acetaldehyde and ethyl butyrate improve the juicy note and 1-p-menthane-8-thiol is responsible for the typical exotic grapefruit character. 

Naringase Naringin Naringenin + carbohydrate Removal of the bitter taste of grapefruit juice. Naringenin is less bitter than naringin. 

The key components of fresh grapefruit juices with a typical grapefruit odour are both isomers of p-mentha-l-en-8-thiol (8-188). The (- -)-(Ji)-enantiomer is present in minute concentrations (less than 1 (xg/kg), but has a very low odour threshold concentration. The (-)-(S)-p-mentha-l-ene-8-thiolhas aweak and non-specific smell. Of the other sulfur compounds, 4-mercapto-4-methylpentan-2-one (8-125) is significant, and also occurs in blackcurrants, some hop cultivars, aromatic wines and basil. A relatively high content of sesquiterpenoids is also typical. The smell and bitter taste of grapefruits arise from (-l-)-nootkatone and (-1-)-8,9-didehydronootkatone. Important odour-active compounds are numerous cyclic ethers, which are likewise found in other essential oils. For example, the essential oil contains about 13% of hnalool oxides that arise from linalool via 5,6-epoxide, and another important epoxide is ( )-4,5-epoxydec-2-enal. The fresh odour of juices is mainly influenced by aliphatic aldehydes, such as acetaldehyde. 

A bitter taste is desirable for some foods, where it is a typical taste. Examples include grapefruits, chicory leaves, cocoa, coffee, beer and tonic drinks. However, sometimes a bitter taste is considered undesirable (ofif-flavour) and the affected foods can have an unacceptable taste and can be even inedible (such as oranges, carrots... 

The flavonoid naringin is the principal component of grapefruit which contributes to the bitter taste of the fruit. 

Nootkatone has a powerful, sweet, and citrus odor and is of importance in grapefruit flavors, contributing to both the aroma and the bitter taste (356). 

The characteristic bitter taste of grapefruit is due to naringin present mainly in the peel. ... 

Another important interaction is that of limonin with the bitter flavanone glycoside naringin. Both of these bitter substances are present in grapefruit juice and Guadagni et al. (25) found that they interact at subthreshold levels in an additive way. Less than threshold amounts of limonin or naringin contribute to the bitterness of a mixture of the two compounds. The bitterness of the mixture can be predicted by adding the taste-unit contribution of each component (taste unit = concentration/ threshold). 

It is difficult to quantitatively define grapefruit qualityTn terms of bitterness because individual taste thresholds and bitterness preferences vary markedly. Guadagni et al. (37) found that 7% of a 27 member taste panel could detect as Tittle as 1.5 ppm naringin in water. Yet, another 7% of that same panel could not distinguish a 50 ppm naringin solution from water alone. 

As previously discussed by Maier and co-workers (Chapter 4), in Navel, Shamouti and certain other orange cultivars, the presence of limonin, a bitter triterpenoid, causes many economic and organoleptic problems and greatly affects the taste quality of processed fruit. Limonin is also prevalent in the grapefruit but the intrinsic quality of this fruit is further complicated by the presence of naringin, a bitter flavanone neohesperidoside (Chapter 5). 

This intense sweetener is made from grapefruit skins and it has a liquorice-like sweet taste. NHDC (9) has long been suggested as a potential intense sweetener but has only recently received legislative approvals. It is 900 times sweeter than sucrose, and chemically NHDC is the open chain analogue of neohesperedin a flavonone which occurs in Seville (bitter) oranges (Citrus aurantum). The dihydrochalcones are flavonoids which are ubiquitous in plants flavonones, chalcones and anthocyanins are also flavonoids. 

The taste of grapefruit juice is acid, fruity, bitter sweet. The peel oil has a characteristic terpeny, woody, exotic fruity character. 

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