Storage retrogradation rate

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. 

Seiko DSC 580 with DSC 10 module heating rate 1 C min" in both the first and second runs sample mass ca 45 mg. The ratio of the heat required for regelatinization (AH2) after storage for 14 days at 5 °C to the heat required for the gelatinization (AH,) is defined as retrogradation ratio. 

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-... 

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