Dextrin: Difference between revisions

{{Pathnav|Dietary supplement|Dietary fiber|frame=1}}

{{横線}}

'''Dextrins''' are a group of low-molecular-weight [[carbohydrate]]s produced by the [[hydrolysis]] of [[starch]] and [[glycogen]]. Dextrins are mixtures of [[polymer]]s of D-[[glucose]] units linked by α-(1→4) or α-(1→6) [[glycosidic bonds]].

Dextrins can be produced from starch using [[enzyme]]s like [[amylase]]s, as during digestion in the human body and during [[Malt#Malting|malting]] and [[mashing]] in beer brewing or by applying dry heat under acidic conditions ([[pyrolysis]] or [[roasting]]). This procedure was first discovered in 1811 by [[Edme-Jean Baptiste Bouillon-Lagrange]]. The latter process is used industrially, and also occurs on the surface of [[bread]] during the baking process, contributing to flavor, color and crispness. Dextrins produced by heat are also known as '''pyrodextrins'''. Starch hydrolyses during roasting under acidic conditions, and short-chained starch parts partially rebranch with α-(1,6) bonds to the degraded starch molecule. See also [[Maillard reaction]].

Dextrins are white, yellow, or brown powders that are partially or fully water-soluble, yielding [[Optical rotation|optically active]] solutions of low [[viscosity]]. Most of them can be detected with [[iodine test|iodine solution]], giving a red coloration; one distinguishes erythrodextrin (dextrin that colours red) and achrodextrin (giving no colour).

White and yellow dextrins from starch roasted with little or no acid are called '''British gum'''.

[[File:Dextrin skeletal.svg|thumb|A dextrin with α-(1→4) and α-(1→6) [[glycosidic bond]]s]]

Yellow dextrins are used as water-soluble [[glue]]s in remoistenable envelope adhesives and paper tubes, in the mining industry as additives in [[froth flotation]], in the [[foundry]] industry as [[green strength]] additives in [[sand casting]], as [[textile printing|printing thickener]] for [[batik]] [[resist dyeing]], and as binders in [[gouache]] paint and also in the leather industry.

White dextrins are used as:  

* a crispness enhancer for [[food processing]], in food batters, coatings, and [[glaze (cooking technique)|glazes]], ([[International Numbering System for Food Additives|INS number]] 1400)  

* a stabilizing agent for certain explosive metal [[Azide | azides]], particularly [[Lead(II) azide]]

Owing to their rebranching, dextrins are less digestible. Indigestible dextrins have been developed as soluble stand-alone [[fiber supplement]]s and for adding to processed food products.

* Maltodextrin

{{Main|Maltodextrin}}

Maltodextrin is a short-chain [[starch]] sugar used as a [[food additive]]. It is also produced by enzymatic hydrolysis from gelled starch, and is usually found as a creamy-[[white]] [[hygroscopic]] spray-dried powder.  Maltodextrin is easily digestible, being absorbed as rapidly as [[glucose]], and might either be moderately [[sweet]] or have hardly any flavor at all.

* Cyclodextrin

{{Main|Cyclodextrin}}

The cyclical dextrins are known as cyclodextrins. They are formed by [[enzymatic]] degradation of starch by certain [[bacteria]], for example, ''[[Paenibacillus macerans]]'' (''Bacillus macerans''). Cyclodextrins have toroidal structures formed by 6-8 [[glucose]] residues.

* Amylodextrin is a linear dextrin or short chained [[amylose]] ([[degree of polymerization|DP]] 20-30) that can be produced by enzymatic hydrolysis of the alpha-1,6 glycosidic bonds or debranching amylopectin. Amylodextrin colors blue with iodine.

*(Beta) Limit dextrin is the remaining polymer produced by enzymatic hydrolysis of [[amylopectin]] with beta [[amylase]], which cannot hydrolyse the alpha-1,6 bonds at branch points.

* Highly branched cyclic dextrin is a dextrin produced from enzymatic breaking of the amylopectin in clusters and using branching enzyme to form large cyclic chains.

* {{annotated link|Brewing}}

* {{annotated link|Cellodextrin}}

* {{annotated link|Starch gelatinization}}

{{wiktionary}}

* {{cite EB9 |wstitle= Dextrin |volume= VII |page=146 |short=1}}

*[https://web.archive.org/web/20070701050826/http://www.cfsan.fda.gov/~dms/eafus.html EAFUS]

{{Carbohydrates}}

{{Authority control}}

{{二次利用}}

[[Category:Edible thickening agents]]

[[Category:Pyrotechnic chemicals]]

[[Category:Starch]]