RETROGRADATION OF AMYLOPECTIN FROM MAIZE AND WHEAT STARCHES

Differential scanning calorimetry was used to study retrogradation of amylopectin (AP) isolated from corn and wheat starches. Corn AP develo ped more crystallinity during storage (as demonstrated by higher entha lpy [DELTAH] values) than did wheat AP; most of the recrystallization occurred during the first week of storage. An increase in onset temper ature of melting (T(o)) (annealing of the crystallites) continued duri ng two weeks of storage. As AP concentration was increased from 25 to 45% (w/v), DELTAH increased and T(o) decreased. Therefore, although mo re crystallites were formed at higher concentrations, those formed at lower concentrations achieved a higher degree of annealing. Retrograda tion effects were determined for some common food additives: NaCl (4%, based on weight of AP); citric acid (3.5%); sodium stearoyl lactylate (0.5%); or sucrose, glucose, and fructose (100%). The DELTAH of corn AP gels were not affected by any of the additives. The DELTAH of wheat AP gels were not affected by sodium stearoyl lactylate or the sugars, but the DELTAH of wheat AP decreased with NaCl. The rate of recrystal lization was changed with citric acid. T(o) of corn AP gel was not aff ected by NaCl or citric acid. The T(o) of wheat AP, however, decreased with NaCl. The rate of annealing decreased with citric acid. T(o) of both amylopectins was decreased by sodium stearoyl lactylate and incre ased by sugars.