Amylopectin retrograded

In the present chapter the effect of sucrose and hydrocolloids (xanthan gum, guar gum, and sodium alginate) on (i) Tg of the freezeconcentrated matrix (7 ), (ii) amylose and amylopectin retrogradation, and (iii) rheological behavior of the system, are analyzed in gelatinized water-starch formulations frozen at different rates and stored at — 18°C. Besides, the importance of Tg as a parameter related to texture quality of starch-sucrose-hydrocolloids-based foods during frozen storage is discussed. 

Recrystallization of amylopectin is a reversible process that can be analyzed by DSC below 100°C (Miles et al., 1985). Amylopectin retrogradation was measured in starch systems containing sucrose from DSC runs immediately after freezing and after 91 days of storage at —80 and — 18°C. Aliquots of gelatinized pastes were run between 20 and 120°C at a heating rate of 10°C min in order to detect the presence of the amylopectin retrogradation peak. 

The addition of sucrose shifted T g towards lower values (onset between — 23 and — 22°C, depending on the system). Thus, commercial storage temperatures (= — 18°C) lie above Tg in starch-sucrose systems, allowing molecular mobility this fact led to amylose and amylopectin retrogradation... 

From the results of the present work, it can be concluded that the storage at the usual commercial temperatures (T = — 18°C slightly above T g) affects the quality of aqueous starch sucrose pastes without gums caused by amylose and amylopectin retrogradation. However, when hydrocolloids are included in the formulations, the usual storage conditions allows main-tainence of acceptable textural attributes. 

Silverio J, Fredriksson H, Andersson R, Ehasson AC, Aman P. The effect of temperature cycling on the amylopectin retrogradation of starches with different amylopectin unit-chain length distribution. Carbohydr Polym 2000 42 175-184. 

Vandeputte GE, Venneylena R, Geeromsb J, Delcoura JA. Rice starches, in. Structural aspects provide insight in amylopectin retrogradation properties and gel texture. J Cereal Sci 2003 38 61-68. 

The formation of crystal nuclei, which proceeds very rapidly at 0 °C and does not occur at temperatures below — 5 °C (Fig. 15.54), determines the rate of amylopectin retrogradation. The nuclei grow most rapidly shortly before the melting point (60 °C) is reached (Fig. 15.54). 

Temperatures above 14 also inhibit staling, e. g., increasing the storage temperature from 21 to 35 decreases the rate of amylopectin retrogradation by a factor of 4 and improves freshness of the crumb, but the aroma is dissipated. Increased protein or pentosan content slows retrogradation. A choice - actually a rule -to extend the shelf hfe or freshness of the baked product is the use of emulsifiers, such as mono-... 

Retrogradation is another important property of starch. It is generally accepted that retrogradation is involved in the staling of baked products such as bread. In particular it appears that retrogradation is the recrystallisation of the amylopectin present. Notably, retrogradation is still a subject of research. The application of techniques such as 13C NMR allows insights that older techniques do not provide. 

Fredriksson, H., Bjork, L, Andersson, R., Liljeberg, H., Silverio, J., Eliasson, A. -C., Aman, P. (2000). Studies on a-amylase degradation of retrograded starch gels from waxy maize and high-amylopectin potato. Carbohydrate Polymers, 43, 81-87. 

Starch (amylose and amylopectin) hydrolysis along with ester-fication, etherification or oxidation have been previously discussed as available methods for producing starch derivatives with improved water dispersibilities and reduced retrogradation potential (, ). Since oxidative and hydrolytic reactions are simple, easily controlled chemical modifications, starch-derived polymers made by hydrolysis alone or oxidative and hydrolytic processes were developed and tested. 

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