| 释义 |
pectic, a. Chem.|ˈpɛktɪk|
[ad. Gr. πηκτικ-ός, f. πηκτ-ός congealed, curdled, f. stem πηγ- of πηγνύειν to make firm or solid.]
a. In pectic acid, a transparent gelatinous substance formed by chemical action from pectin, and forming an important constituent of fruit-jellies. Also, of or pertaining to pectin.
(By further transformation it is converted into parapectic acid (para- 2 a) and metapectic acid.) pectic fermentation, the fermentation supposed to be produced by pectase, which converts pectin into pectic and other related acids.
1831T. Thomson Chem. Inorg. Bodies (ed. 7) II. 120 Braconnot gave it the name of pectic acid, from the great tendency which it has to form a jelly with water. 1863Mitchell Farm of Edgewood 225 Pears have a modicum of pectic acid at a certain stage of their ripeness. 1866–77Watts Dict. Chem. IV. 363 Under the influence of acids or alkalis, pectin is gradually modified, and ultimately transformed into a strongly acid compound called metapectic acid, passing however through a series of intermediate modifications called by Frémy parapectin, metapectin, pectosic acid, pectic acid, and parapectic acid. 1893Syd. Soc. Lex., Pectase, an organic albuminoid ferment found in unripe fruits and roots, which determines the Pectic fermentation. 1930[see galacturonic a.]. 1964D. D. Davies et al. Plant Biochem. iii. 147 Pectic acid is the simplest pectic substance and is the basis of the others. Pure pectic acid appears to be an unbranched chain of α-1,4 linked D-galacturonic acid units which are present in the C-1 chair form..of the pyranose ring. Any compound of this structure which is large enough to possess colloidal properties is classed as a pectic acid. Most pectic acids appear to contain about 100 units with a minimum of approximately 5 units. 1972[see pectinase].
b. Applied to a class of substances that includes the pectins and other colloidal polymers of galacturonic acid.
1889Chem. News 1 Nov. 221/2 The author [sc. L. Mangin] shows the presence of pectic compounds in vegetable membranes. 1913Haas & Hill Introd. Chem. Plant Products ii. 126 Comparatively little is known about the chemistry of pectin or the pectic bodies, as there appear to be several of these substances. 1957E. V. Miller Chem. Plants i. 14 Pectin is perhaps the pectic compound with which the layman is most familiar. 1966R. M. Devlin Plant Physiol. vii. 137 During the ripening of the fruit, protopectin is converted into the more soluble pectic substances—pectin and pectic acid. 1973J. A. Goss Physiol. Plants xvi. 344 In contrast to the other pectic substances, pectin is water-soluble, and is located in the protoplasm of the cell. |