| 释义 |
pectin Chem.|ˈpɛktɪn|
[f. stem pect- of pectic + -in1.]
1. a. A white neutral substance, soluble in water, formed from pectose by heating with acids, or naturally in the ripening of fruits, and constituting the gelatinizing agent in vegetable juices; in the further process of ripening, it is converted into parapectin (para- 2 a), metapectin, and other related substances (see pectic). Now recognized as having a variable composition but being principally a high-molecular-weight polymer of partially methylated galacturonic acid in which galactose and arabinose residues are also present.
1838T. Thomson Chem. Org. Bodies 146 Vauquelin, who found pectin in the tamarind, considered it as the same with pectic acid. 1866–77Watts Dict. Chem. IV. 364 Green fruits..do not contain pectin ready formed, but only pectose... When the fruit is ripe, the juice..contains a large quantity of pectin, and still more of parapectin... Lastly, fruits in the over-ripe state no longer contain a trace of pectin, that substance having been converted into metapectic acid. 1913, etc. [see pectic a. b]. 1917,1930[see galacturonic a.] 1964B. Nilson Pears Family Cookbk. 223/2 Over-ripe fruit will not set so well because it will contain less pectin. 1972Materials & Technol. V. xix. 703 Pectins, which occur only in certain plant tissues, are polymers of galacturonic acid linked by α-1,4-glycosidic units, with about two thirds of the carboxylic acid groups esterified with methanol. 1975D. Green Food & Drink from your Garden i. vii. 65 Flowers yield very little sugar, but their musts will release no pectins (the glue-like substances holding plant tissues together) and so will clear easily.
b. Any of the pectic substances.
1896Jrnl. Chem. Soc. LXX. i. 7 Pectin Substances... Many attempts have been made to establish a relationship between pectins and vegetable gums (carbohydrates). 1929R. A. Gortner Outl. Biochem. xxvii. 584 The pectin producing these jellies is the only water-soluble member of a group of related compounds known as the ‘pectic substances’, or sometimes called the ‘pectins’. 1931E. C. Miller Plant Physiol. i. 12 It is now fairly well established that these substances are not chemically combined with cellulose, although they are closely associated with it, so that they are classified under the general name of the ‘pectic compounds’ or ‘pectins’. 1966Nowakowski & Clarke tr. Kretovich's Princ. Plant Biochem. ii. 86 The ripening of fruits is characterized by the conversion of insoluble into soluble pectin.
†2. attrib. in the sense of pectic a. b. Obs.
1877Jrnl. Chem. Soc. XXXII. 502 The formula of the group of pectin bodies. 1895F. E. Weiss tr. Sorauer's Pop. Treat. Physiol. Plants vi. 123 Together with gums and acids we often find substances consisting also of carbon, hydrogen, and oxygen, which form gelatinous masses on boiling, and are termed pectin substances. 1900A. J. Ewart tr. Pfeffer's Physiol. Plants I. viii. 477 Many gums..seem to be in part allied to pectin substances.
Hence pectinaceous |-ˈneɪʃəs| a., related to or containing pectin.
1844Dunglison Med. Lex. s.v. Pectinous, A pectinous or pectinaceous vegetable principle. 1887tr. Sachs' Physiol. Plants 328 The share in metabolism taken by some other organic compounds, such as pectinaceous substances. |