Gelatinization involves loss of starch granule structure and disruption of crystallinity. Table 2 also shows DSC thermal properties of noodles steamed for different periods of time. The results revealed that after steaming, control noodles showed lower onset and peak temperature of gelatinization than other noodles, which was due to the effect of salt or alkaline salt on the gelatinization. It has been reported that two effects of salts (effect on water activity and on starch) may conflict with each other and result in complex effect patterns depending on the concentration of salts (Chiotelli Pilosio, & Le Meste, 2002) In this study, salt and alkaline salt in noodle might act as gelatinization inhibitors by rupturing hydrogen bonds and lowering water activity, resulting in increased gelatinization temperature. Onset and peak temperature of starch galatinization in steamed noodles increased, which was consistent to the increased pasting temperature as measured by RVA, while gelatinization enthalpy dramatically upon steaming. Gelatinization enthalpy in control noodles disappeared after 2 min of steaming, while the enthalpy disappeared after 1 min for white noodles and yellow alkaline noodles. Generally, the lack of galatinization endotherm meant the sample was completely gelatinized.
Park and Baik (2004) found a similar decrease in gelatinization enthalpy in white salted noodles after 2 min of cooking. The results indicated that the rate of starch gelatinization in noodle was rapid. However, the result was not in accordance with the tendency obtained from RVA, which was due ferences between viscosity properties and thermal properties. These changes in pasting properties and thermal properties of steamed noodles indicated that at limiting water conditions starch gelatinization occurred, which further accounted for the effect of steaming on noodle and the quality of frozen cooked noodles.