Bitter substances

As was mentioned earlier, bitter substances are composed of a broad range of chemical structures, thus, there often is little commonality in structure to permit the utilization of a single analytical approach. Methods for this analysis have to be designed for each bitter component (or group of components) to be analyzed. There are numerous methods in the literature, most depending upon HPLC since bitter substances are typically nonvolatile [98,109,110]. 

Hollowood, T.A., J.M. Davidson, L. DeGroot, R.S.T. Linforth, A.J. Taylor, Taste release and its effect on overall flavor perception, in Chemistry of Taste Mechanisms, Behavior, and Mimics, P.G.D. Paredes, Ed., Amer. Chem. Soc., Washington, D.C., 

Volatile Compounds in Foods, AJ Zeist, The Netherlands, Nutrition and Food Research, Utrechtseweg, 1995. 

Seifert, R.M.B., R.G. Guadagni, D.G. Black, G. Harris, Synthesis of some 2-methoxy-3-alkylpyrazines with strong bell pepper-like aromas, J. Agric. Food Chem., 18, p. 246, 1970. 

MarsUi, R., Ed., Flavor, Fragrance, and Odor Analysis, Marcel Dekker, New York, 2002, p. 425. 

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When food contains both sweet and bitter substances, the temporal pattern of reception, ie, the order in which sweet and bitter tastes are perceived, affects the total quaUtative evaluation. This temporal effect is caused by the physical location of taste buds. The buds responding to sweet are located on the surface and the tip of the tongue, the bitter in grooves toward the rear. Therefore, the two types of taste buds can be activated sequentially. 

In the extraction of citms juices it is desirable to have as gende an extraction pressure as possible. There should be minimal contact time between juice and pulp to reduce the amount of bitter substances expressed from the peel into the juice. The amount of suspended soHds in citms juice is controlled in a subsequent separation in a finisher. A screw action is used to force the juice through a perforated screen and separate the larger pulp particles from the juice. The oil level in the juice is adjusted by vaporizing under a vacuum (10). The separated pulp is washed and finished several times to produce a solution which is then either added back to the juice to increase juice yield, or concentrated to produce pulp wash soHds, also called water extract of orange soHds, which can be used as a cloudy beverage base. 

Beer taste can be spoiled by contaminating bacteria or yeasts. The most common bacteria are lactic and acetic acid producers and T ymomonas. Wild yeasts can be anything other than the intended strain S. uvarum is considered a contaminant of ale fermentations and S. cerevisiae a contaminant of lager fermentations. The common wild yeast contaminants are S. diastaticus and species of Picbia, Candida and Brettanomjces. It may be noted that the flavor of beer may be improved by the ability of yeast to adsorb bitter substances extracted from hops, such as humulones and isohumulones. 

By far the most important constituents of hops are the bitter substances, humulones (a-acids), lupulones (P-acids), and then oxidation products. 

Stomach and intestinal ulcers. 8.3 Side effects Occasionally, headaches may be caused in people who are sensitive to bitter substances. 8 4 Dosage and manner of use Boiling water (ca. 150 ml) is poured over two tea-spoonfuls of the Lea, covered and allowed to draw for 5 10 min, and then passed through a tea strainer. If not otherwise pre.scribed, a cup of the fresh and 8.2 Dosage and manner of use Boiling water fca. 150 ml) is poured over a table-spoonful of the tea, covered and allowed to draw for ca. 10 min., and then passed through a tea strainer. 11 not otherwise prescribed, a cup of the freshly prepared tea is drunk warm several times a day between meals. 8.3 Note Store protected from light and moisture. 

The taste of aqueous quinine hydrochloride solution with and without sucrose was examined in four volunteers (males, aged 23 28). All considered 1 mM quinine hydrochloride quite bitter, ImM quinine hydrochloride and 100mM sucrose bitter-sweet, and 1 mM quinine hydrochloride and 500 mM sucrose sweet though bitter. Sucrose is thus shown to lessen the bitterness of quinine hydrochloride solution, as generally already known. Quinine hydrochloride and sucrose are bitter and sweet substances, respectively, and thus a sweet substance may alter oscillation, when a bitter substance is present, to that corresponding to a sweet substance. 

Effects of Sesquiterpene Lactones on Seed Germination. Sesquiterpene lactones are common constituents of the Asteraceae but are also found in other angiosperm families and in certain liverworts (31,32). These highly bitter substances exhibit a wide spectrum of biological activities (J 3) which include cytotoxicity, anti-tumor, anti-microbial, insecticidal (34) and molluscicidal (35) properties. Furthermore, they are known causes for livestock poisoning and contact dermatitis in humans (33). Structure-activity relationship studies on sesquiterpene lactones have demonstrated that biological activity frequently depend on the presence of the cr... 

Bitter taste can be masked by sweeteners, by salt or by dipeptides containing aspartic or glutamic acids (22,25,24,25). The bitter-masking potential of sugars wife quinine was recently assessed, and quinine-equivalent values were derived to predict masking ability of these substances. Attenq)ts to mask bitter taste may be successful only wife certain bitter substances. 

The true scientific era of the salicylates began in England in 1763, when the Reverend Edward Stone presented a report to the Royal Society on the use of willow bark as a fever treatment. Stone was a believer in the rather curious Doctrine of Signatures, which maintained that one could find cures where the diseases themselves were spawned. Since fevers were often associated with swamps, probably because of mosquito-borne infectious agents, Stone searched swamplands for cures. He tasted a sprig of willow and was stunned by its bitterness. Aware that quinine, an equally bitter substance, was useful in the treatment of malarial fever. Stone decided to give willow... 

The extraction of the bitter substance of hops is a complex process. During boiling and subsequent fermentation, large losses of bitter substances are incurred, and only 25—30% of the bitter substances in hops are present in the finished beer. The amount of loss depends on composition of the wort, pH, etc. Much of these bitter substances is adsorbed by the warm sludge and is lost during its separation. Wort boiling takes place in the wort kettle or copper of various constructions. An example appears in Figure 7. 

Dried raw hops contain about 13 to 23% bitter substances, as... 

The yields of bitter substances in the CO2 extracts are similar to those obtained with pellets and dichloromethane extracts. The long term stability of the beer is similar to the others. 

CC>2-Extraction of cloves gives a yield of 18 to 25% with extraction conditions of 350 bar and 65°C. The extraction pressure should not be too high, otherwise waxes and bitter substances enter the extract. The content of volatile oil is more than 80%, of which the content of Eugenol is around 70%. 

A Forster. Investigation by means of HPLC of hop bittering substances in beer during different ageing conditions. Proc Conv Inst Brew (Aust NZ Sect) Brisbane 20 109-117, 1988. 

R Franiau, R Mussche. Quantitative determination of hop bitter substances and their derivatives in hop extracts by thin layer chromatography. J Inst Brew 80 59-67, 1974. 

I McMurrough, JR Byrne. HPLC analysis of bittering substances, phenolic compounds, and various compounds of alcoholic beverages. In LML Nollet, ed. Food Analysis by HPLC. New York Marcel Dekker, 1992, pp 579-641. 

This small tropical family produces tubers which are used in some regions as food after the removal of bitter substances. 

Many bitter substances have been mentioned as substitutes for hops, but they are very seldom found in beer. 

The complete examination for these bitter substances is long and complicated and does not always give certain results reference may be made to special publications on the subject. A short test, which is sufficient in many cases, is as follows 100 c.c. of the beer are evaporated to about one-half the volume, basic lead acetate being then added until no further precipitation occurs. The liquid is next filtered and the excess of lead in the filtrate precipitated with ammonium sulphate. If, after being again filtered, the liquid has a distinctly bitter flavour, the presence of extraneous bitter substances is indicated. 

They vary widely in composition, but in general may be divided into Liqueurs free from sugar, such as absinthe liqueurs containing sugars and bitter substances, termed bitters, and true liqueurs, which contain sugars and essential oils or vegetable extracts. 

Investigation of the Bitter Substances.—For the complete investigation of the various injurious bitter principles, reference must be made to the special articles in books dealing with the subject.2... 

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