Retrogradation (starch)

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Retrogradation is a reaction that takes place when the amylose and amylopectin chains in cooked, gelatinized starch realign themselves as the cooked starch cools.[1]

When native starch is heated and dissolves in water, the crystalline structure of amylose and amylopectin molecules is lost and they hydrate to form a viscous solution. If the viscous solution is cooled or left at lower temperature for a long enough period, the linear molecules, amylose, and linear parts of amylopectin molecules retrograde and rearrange themselves again to a more crystalline structure. The linear chains place themselves parallel and form hydrogen bridges. In viscous solutions the viscosity increases to form a gel. At temperatures between –8 and +8 °C the aging process is enhanced drastically.

Retrogradation can expel water from the polymer network. This is a process known as syneresis. A small amount of water can be seen on top of the gel. Retrogradation is directly related to the staling or aging of bread.[2]

Retrograded starch is less digestible (see resistant starch).

Chemical modification of starches can reduce or enhance the retrogradation. Waxy, high amylopectin, starches also have a much lesser tendency to retrogradate. Additives such as fat, glucose, sodium nitrate and emulsifier can reduce retrogradation of starch.

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References[edit]

  1. ^ Wang, Shujun; Li, Caili; Copeland, Les; Niu, Qing; Wang, Shuo (2015-09-01). "Starch Retrogradation: A Comprehensive Review". Comprehensive Reviews in Food Science and Food Safety 14 (5): 568–585. doi:10.1111/1541-4337.12143. ISSN 1541-4337. 
  2. ^ Cereals in breadmaking: a molecular colloidal approach, Ann-Charlotte Eliasson, Kåre Larsson, CRC Press, 1993, pages: 126-129, ISBN 0-8247-8816-8, ISBN 978-0-8247-8816-2

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