Fruits citrus

M.p. 190-192 C. The enolic form of 3-oxo-L-gulofuranolactone. It can be prepared by synthesis from glucose, or extracted from plant sources such as rose hips, blackcurrants or citrus fruits. Easily oxidized. It is essential for the formation of collagen and intercellular material, bone and teeth, and for the healing of wounds. It is used in the treatment of scurvy. Man is one of the few mammals unable to manufacture ascorbic acid in his liver. Used as a photographic developing agent in alkaline solution. 

Loss of a proton from the tertiary carbocation formed m this step gives limonene an abundant natural product found m many citrus fruits Capture of the carbocation by water gives a terpmeol also a known natural product... 

Sabinene is a monoterpene found in the oil of citrus fruits and plants It has been synthe sized from 6 methyl 2 5 heptanedione by the sequence that follows Suggest reagents suitable for carrying out each of the indicated transformations... 

Crude turpentine is distilled to obtain refined products used in the fragrance and flavour industry. Only the unsaturated mono- and bicyclic terpenes are of interest for resin production. These are mainly a-pinene, p-pinene and dipentcne (D,L-limonene) (Fig. 17). D-Limonene is obtained by extraction of orange peel in citrus fruits. 

Polyterpenes. Polyterpenes is one of the first classes of non-polar tack-ifiers to be developed. Terpene monomers are a by-product in the extraction of rosin from wood stumps or tree sap, and from the extraction of oils from citrus fruits. The latter is the dominant source. As such, polyterpene prices generally mirror those of citrus fruits, which fluctuate substantially from one growing season to the next. Terpenes like rosin are cyclic, see Fig. 6, which is partly responsible for their excellent solvent properties. 

Tinplate that meets the rigid specifications imposed by these controls is sometimes supplied as special quality material and undoubtedly can give improved shelf-life, particularly with citrus fruits. The A.T.C. value has probably more effect on shelf-life determined by hydrogen swell than any other factor. 

Ascorbic acid, H2C6H606, also known as vitamin C, is present in many citrus fruits. It is a diprotic acid with the following values = 7.9 X 105 K = 1-6 X 10 12. What is the pH of a 0.63 M solution of ascorbic acid Estimate [HC6H606-] and [C4H6062-]. 

Prepare a buffer solution (pH 4.5) by dissolving 6 g acetic (ethanoic) acid and 13,6 g sodium acetate in 1 L of distilled water. Pipette 10 mL of a commercial sample of citrus fruit juice into a 1 L graduated flask and make up to the mark with oxygen-free water,... 

The world demand for citric add around 1900 amounted to some 10,000 tonnes per annum. This was realised by pressing citrus fruits and precipitation of the citric add as calcium titrate. An Italian, government-led cartel had virtual monopoly of this process and as such the price of citric add was very high. 

Mas is also proudly American. The bartender working on Wednesday, Andrew blunter, curly-headed and all-American, could have been playing John Adams in a college production of 1116. (A server walked by with a black spike Mohawk. He must be playing the natives. It s the West Village, isn t it ) And die ginger daiquiri, which Mr. Hunter developed widi Thomas Wilson, an owner, has Meyer lemon juice in it (as well as Cointreau), a citrus fruit popularized by new American chefs. 

Ascorbic acid is photosensitive and unstable in aqueous solution at room temperature. During storage of foods, vitamin C is inactivated by oxygen. This process is accelerated by heat and the presence of catalysts. Ascorbic acid concentration in human organs is highest in adrenal and pituitary glands, eye lens, liver, spleen, and brain. Potatoes, citrus fruits, blade currants, sea buckthorns, acerola, rose hips, and red paprika peppers are among the most valuable vitamin C sources [1,2]. 

Citric acid, which is extracted from citrus fruits and pineapples, undergoes three successive deprotonations with pK, values of 3.14, 5.95, and 6.39. Estimate the pH of (a) a 0.15 m aqueous solution of the monosodium salt (b) a 0.075 M aqueous solution of the disodium salt. 

The two examples of sample preparation of solids containing low concentrations of the substances of interest will be the analysis of aflatoxins in corn meal (7) and the determination of the fungicide thiabendazole in citrus fruits. It should be pointed out that the applications chosen in this section attempt to reflect a range of analyses that the analyst is likely to meet in both research and industrial laboratories. 

Chromatogram of Thiabendazole Extracted from Citrus Fruits... 

The next major discovery in this field, which was the result of a joint research effort in 1968 between M and T Chemicals, Inc., and the Dow Chemical Company in the United States (475, 524), was that tricyclo-hexyltin hydroxide ("Plictran ) possesses a very high activity against certain types of mites, and this compound was subsequently introduced by Dow as an acaricide for use on apple, pear, and citrus-fruit trees. A second triorganotin acaricide, bis(trineophyltin) oxide ("Vendex or "Torque ), has recently been introduced by Shell Chemical Company (476). Two other tricyclohexyltin compounds are currently under de-... 

A method has been reported for the quantification of five fungicides (shown in Figure 5.39) used to control post-harvest decay in citrus fruits to ensure that unacceptable levels of these are not present in fruit entering the food chain [26]. A survey of the literature showed that previously [27] APCl and electrospray ionization (ESI) had been compared for the analysis of ten pesticides, including two of the five of interest, i.e. carbendazim and thiabendazole, and since it was found that APCl was more sensitive for some of these and had direct flow rate compatibility with the HPLC system being used, APCl was chosen as the basis for method development. 

Figure 5,39 Structures of various fungicides used in the control of post-harvest decay in citrus fruits. Reprinted from J. Chrormtogr., A, 912, Fernandez, M., Rodriguez, R., Pico, Y. and Manes, J., Liquid chromatographic-mass spectrometric determination of post-harvest fungicides in citrus fruits , 301-310, Copyright (2001), with permission from Elsevier Science.

Citrus fruits from markets in Spain were analyzed for residues of methyl parathion along with other organophosphorus insecticides (Torres et al. 1997). Of the 171 orange samples analyzed, 14 had levels of methyl parathion <0.2 ppm, while 5 had levels >0.2 ppm. Levels ranged from the 0.1 ppm limit of detection to 3.8 ppm depending on the type of orange. Of the 15 grapefruit samples analyzed, 1 was found to contain methyl parathion at a level of 0.3 ppm. 

Torres CM, Pico Y, Marin R, et al. 1997. Evaluation of organophosphoms pesticide residues in citrus fruits from the Valencian community (Spain). J Assoc Off Anal Chem 80 1122-1128. 

Carboxylic acids with one acid group are known as monobasic acids while those with two acid groups are dibasic acids. All acids with more than one acid group are in the class of polybasic acids. The simplest organic acid, formic acid, is responsible for the irritation of bee and ant stings. Vinegar is a 5% solution of acetic acid in water. The acetic acid is responsible for the characteristic sour taste. Citric acid, found in citrus fruits and used in soft drinks, is a tribasic acid with three carboxylic acid groups. The dibasic acid, adipic acid, is a major component of nylon. 

Of this class of naturally occurring, sweet compounds, the flavanone glycosides found in citrus fruits have achieved considerable interest, owing to the systematic studies of Horowitz and Gentili " (see Fig. 20). 

Our molecular inset shows citric acid, which has three carboxylic acid functional groups. Citric acid is present in all citrus fruits as well as many other tart-tasting foods, including berries, pineapples, pears, and tomatoes. Lemons are acidic because they contain as much as 3% citric acid by mass. 

Carrots were also the main sonrces of a-carotene, whereas tomatoes and tomato prodncts were the major sources of lycopene. Lutein was mainly provided by peas in the Republic of Ireland and United Kingdom. Spinach was found to serve as the major source in other countries. Lutein and zeaxanthin xanthophylls are found in a wide variety of fruits and vegetables, particularly green leafy vegetables, but also in some animal products such as egg yolks. In all countries, P-cryptoxanthin was obtained primarily from citrus fruits. 

Carotenoids and prostate cancer — Numerous epidemiological studies including prospective cohort and case-control studies have demonstrated the protective roles of lycopene, tomatoes, and tomato-derived products on prostate cancer risk other carotenoids showed no effects. " In two studies based on correlations between plasma levels or dietary intake of various carotenoids and prostate cancer risk, lycopene appeared inversely associated with prostate cancer but no association was reported for a-carotene, P-carotene, lutein, zeaxanthin, or p-cryptoxanthin. - Nevertheless, a protective role of all these carotenoids (provided by tomatoes, pumpkin, spinach, watermelon, and citrus fruits) against prostate cancer was recently reported by Jian et al. ... 

Kato, M. et al.. Accumulation of carotenoids and expression of carotenoid biosynthetic genes during maturation in citrus fruit. Plant Physiol. 134, 82, 2004. Cunningham, F.X. Jr. and Gantt, E., One ring or two Determination of ring number in carotenoids by lycopene epsilon-cyclases, Ptvc. Natl. Acad. Sci. USA 98, 2905, 2001. 

Rouse, A.H. 1953. Distribution of pectinesterase and pectin in component parts of citrus fruits. Food Technol. 7 360-362. 

Cold-pressed essential oils from the peel are some of the most important by-products recovered during the processing of Citrus fruits. The presence of limonene in the aqueous discharges, with its antimicrobial activity [1], decreases the effectiveness of the waste treatment system and increases the time necessary for the biological breakdown of the organic matter produced in the peel oil recovery system [2,3]. Additional recovery of essential oils from waste water would increase industry s returns and reduce the pollution problems associated with the disposal of waste water [4,5]. Several methods for reducing the levels of residual essential oils in the aqueous effluent have been developed over the years [6-11]. 

To remove the essential oil from the peel of citrus fruits, the oil glands, which are located in the flavedo (the outer coloured portion of the peel), are ruptured by mechanical systems. The oil is washed away with a spray of water to produce an oil-in-water emulsion with small peel particles. To prevent absorption of the essential oil by the spongy albedo (the iimer white portion of the peel), this emulsion is passed through a screening device (finisher) of 0.5 to 0.7 mm in diameter, which removes the coarsest particles of the fruit peels [12]. 

---