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[ren-in] /ˈrɛn ɪn/
noun, Biochemistry
a coagulating enzyme occurring in the gastric juice of the calf, forming the active principle of rennet and able to curdle milk.
1895-1900; renn(et) + -in2 Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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British Dictionary definitions for rennin


an enzyme that occurs in gastric juice and is a constituent of rennet. It coagulates milk by converting caseinogen to casein Also called chymosin
Word Origin
C20: from rennet + -in
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Word Origin and History for rennin

milk-curdling enzyme, 1897, from rennet + -in (2).

Online Etymology Dictionary, © 2010 Douglas Harper
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rennin in Medicine

rennin ren·nin (rěn'ĭn)
A milk-coagulating enzyme found especially in the gastric juice of the fourth stomach of young ruminants, used in making cheeses and junkets. Also called chymosin.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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rennin in Science
An enzyme that catalyzes the coagulation of milk. Rennin is found in the gastric juice of the fourth stomach of young ruminants and is used in making cheese. Also called chymosin.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Article for rennin

protein-digesting enzyme that curdles milk by transforming caseinogen into insoluble casein; it is found only in the fourth stomach of cud-chewing animals, such as cows. Its action extends the period in which milk is retained in the stomach of the young animal. In animals that lack rennin, milk is coagulated by the action of pepsin (q.v.), as is the case in humans. A commercial form of rennin, rennet, is used in manufacturing cheese and preparing junket.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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