Retrogradation (starch) (original) (raw)
Retrogradation ist die Rückbildung zuvor verkleisterter Stärke. Dies geschieht hauptsächlich mit der in der Stärke enthaltenen Amylose, da diese, im Gegensatz zu Amylopektin, nicht aus einem dreidimensionalen Glucose-Netzwerk aufgebaut ist und daher das Wasser nicht so gut fixieren kann.
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| dbo:abstract | Retrogradation ist die Rückbildung zuvor verkleisterter Stärke. Dies geschieht hauptsächlich mit der in der Stärke enthaltenen Amylose, da diese, im Gegensatz zu Amylopektin, nicht aus einem dreidimensionalen Glucose-Netzwerk aufgebaut ist und daher das Wasser nicht so gut fixieren kann. Retrogradation ist in erster Linie die Ursache für Altbackenwerden von Gebäcken. Die im Mehl befindliche Stärke gibt dabei die physikalisch gebundene Flüssigkeit teilweise wieder ab und geht in einen kristallinen Zustand über (z. B. Stärkekörner). Das dadurch altbackene Gebäck nimmt eine weiche, schaumgummiartige Konsistenz an. Die Retrogradation der Stärke wird durch niedrige Temperaturen stark begünstigt. Zwischen −7 und +7 °C verstärkt sich die Alterung um den Faktor drei. Da die Retrogradation um den Gefrierpunkt besonders schnell verläuft, sollten frische Backwaren nicht im Kühlschrank gelagert werden.Die Verhärtungswirkung lässt sich durch Zugabe von Fetten, Emulgatoren und α-Amylase verzögern. (de) Retrogradation is a reaction that takes place when the amylose and amylopectin chains in cooked, gelatinized starch realign themselves as the cooked starch cools. When native starch is heated and dissolved 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. Amylose crystallization occurs much faster than crystallization of the amylopectin. The crystal melting temperature of amylose is much higher (about 150 ℃) than amylopectin (about 50–60 ℃). The temperature range between cooking starch and storing in room temperature is optimum for amylose crystallization, and therefore amylose crystallization is responsible for the development of initial hardness of the starch gel. On the other hand, amylopectin has a narrower temperature range for crystallization as crystallization does not occur at a temperature higher than its melting temperature. Therefore, amylopectin is responsible for development of the long-term crystallinity and gel structure. Retrogradation can expel water from the polymer network. This process is 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. Retrograded starch is less digestible (see resistant starch). Chemical modification of starches can reduce or enhance the retrogradation. Waxy, high amylopectin, starches also have much less of a tendency to retrogradate. Additives such as fat, glucose, sodium nitrate and emulsifier can reduce retrogradation of starch. (en) Il fenomeno della retrogradazione dell'amido è alla base della formazione del pane raffermo e può essere considerato come l'inverso della gelatinizzazione: esso consiste nella tendenza da parte dell'amido a riassumere la struttura originaria. Il raffermamento è il processo che causa il deterioramento (il diventare raffermo) del pane e di altri cibi ricchi di carboidrati complessi. Sebbene l'amido in realtà non riesca mai a tornare in una configurazione simile a quella iniziale, si forma una struttura intermedia rigida dovuta all'avvicinamento delle catene di amilosio e alla crescita di cristalli di amilopectina. La quantità di amido retrogradato è quindi direttamente proporzionale al contenuto di amilosio. Quando con il passare del tempo, nel caso del pane, si verifica la migrazione dell'acqua verso la crosta esterna si ha la cristallizzazione dei componenti amilacei con conseguente aumento della consistenza (pane raffermo). La digeribilità in questo caso diminuisce, anche se la retrogradazione dell'amido sembra collegata ad una riduzione del cancro al colon. Il fenomeno di retrogradazione è massimo alla temperatura di circa -3 °C, mentre viene ritardato dal congelamento. (it) Retrogradacja skrobi – zjawisko polegające na przemianie formy spiralnej skrobi w liniową i porządkowaniu się wyprostowanych łańcuchów amylozy w zwarte micele, których strukturę stabilizują wiązania wodorowe, tworzące się między grupami hydroksylowymi cząsteczek skrobi położonych blisko siebie. Proces retrogradacji jest szczególną cechą kleików i żeli skrobiowych. Tendencję do retrogradacji wykazują przede żele zawierające duże ilości amylozy. Natomiast amylopektyna, ze względu na jej rozgałęzioną strukturę, hamuje retrogradację. Powstające w czasie retrogradacji agregaty (micele) są nierozpuszczalne w zimnej wodzie i wydzielają się one z kleików skrobiowych w formie dendrytów. Konsekwencją procesu retrogradacji jest zmniejszenie przestrzeni międzycząsteczkowych, co prowadzi do eliminacji wody z makrostruktury kleiku lub żelu i odwodnienia tego materiału (synerezy). (pl) |
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| rdfs:comment | Retrogradation ist die Rückbildung zuvor verkleisterter Stärke. Dies geschieht hauptsächlich mit der in der Stärke enthaltenen Amylose, da diese, im Gegensatz zu Amylopektin, nicht aus einem dreidimensionalen Glucose-Netzwerk aufgebaut ist und daher das Wasser nicht so gut fixieren kann. (de) Retrogradation is a reaction that takes place when the amylose and amylopectin chains in cooked, gelatinized starch realign themselves as the cooked starch cools. When native starch is heated and dissolved 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. Amylose crystallizati (en) Il fenomeno della retrogradazione dell'amido è alla base della formazione del pane raffermo e può essere considerato come l'inverso della gelatinizzazione: esso consiste nella tendenza da parte dell'amido a riassumere la struttura originaria. Il fenomeno di retrogradazione è massimo alla temperatura di circa -3 °C, mentre viene ritardato dal congelamento. (it) Retrogradacja skrobi – zjawisko polegające na przemianie formy spiralnej skrobi w liniową i porządkowaniu się wyprostowanych łańcuchów amylozy w zwarte micele, których strukturę stabilizują wiązania wodorowe, tworzące się między grupami hydroksylowymi cząsteczek skrobi położonych blisko siebie. Proces retrogradacji jest szczególną cechą kleików i żeli skrobiowych. Tendencję do retrogradacji wykazują przede żele zawierające duże ilości amylozy. Natomiast amylopektyna, ze względu na jej rozgałęzioną strukturę, hamuje retrogradację. (pl) |
| rdfs:label | Retrogradation (Chemie) (de) Retrogradazione dell'amido (it) Retrogradation (starch) (en) Retrogradacja skrobi (pl) |
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