Cereal Chem. 78(2): [186][187][188][189][190][191][192] Differential scanning calorimetry (DSC) was used to study the effect of sucrose on wheat starch glass transition, gelatinization, and retrogradation. As the ratio of sucrose to starch increased from 0.25:1 to 1:1, the glass transition temperature (T g , T g ′) and ice melting enthalpy (∆H ice ) of wheat starch-sucrose mixtures (with total moistures of 40-60%) were decreased to a range of -7 to -20°C and increased to a range of 29.4 to 413.4 J/g of starch, respectively, in comparison with wheat starch with no sucrose. The T g ′ of the wheat starch-sucrose mixtures was sensitive to the amount of added sucrose, and detection was possible only under conditions of excess total moisture of >40%. The peak temperature (T m ) and enthalpy value (∆H G ) for gelatinization of starch-sucrose systems within the total moisture range of 40-60% were increased with increasing sucrose and were greater at lower total moisture levels. The T g ′ of the starchsucrose system increased during storage. In particular, the significant shift in T g ′ ranged between 15 and 18°C for a 1:1 starch-sucrose system (total moisture 50%) after one week of storage at various temperatures (4, 32, and 40°C). At 40% total moisture, samples with sucrose stored at 4, 32, and 40°C for four weeks had higher retrogradation enthalpy (∆H) values than a sample with no sucrose. At 50 and 60% total moisture, there were small increases in ∆H values at storage temperature of 4°C, whereas recrystallization of samples with sucrose stored at 32 and 40°C decreased. The peak temperature (T p ), peak width (δT), and enthalpy (∆H) for the retrogradation endotherm of wheat starch-sucrose systems (1:0.25, 1:0.5, and 1:1) at the same total moisture and storage temperature showed notable differences with the ratio of added sucrose. In addition, T p increased at the higher storage temperature, while δT increased at the lower storage temperature. This suggests that the recrystallization of the wheat starch-sucrose system at various storage temperatures can be interpreted in terms of δT and T p .The phase transitions associated with ordering and disordering, such as glass transition, gelatinization, and retrogradation in starch systems have been intensively investigated with differential scanning calorimetry (DSC) (Donovan 1979; Zeleznak and Hoseney 1987a,b;Slade and Levine 1988;Kalichevsky et al 1992).The glass transition temperature (T g , T g ′) in starch decreases with increasing water content due to the plasticization effect of water (Slade and Levine 1987). The T g of starch systems with water contents >20% drops below room temperature (Zeleznak and Hoseney 1987a) and below 0°C for water contents ≥50% (Slade and Levine 1988). At temperatures below T g , the material becomes a glassy solid and molecular motion is so slow that crystallization does not occur in a realistic period of time. At temperatures above T g , however, the material is a rubbery liquid and sufficient motion of the polymer can occur, allowing a retro...

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