Changes in Morphological Characteristics, Crystallinity, and Thermodynamic Properties of Starches during Deep-fat Frying

Abstract:

A deep-fat-frying (DFF) model was employed to study the changes in morphological characteristics, crystal structure, and thermodynamic characteristics of starches during the DFF process using advanced analytical methods, including scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and X-ray diffractometry (XRD). The SEM results indicated that there were significant changes in the morphological characteristics of starch granules with increasing frying temperature and time. During the initial frying, the granules expanded. As frying proceeded, the starch granules disintegrated, moved close to each other, and ultimately merged to form large aggregates. Simultaneously, the iodine blue value of starch decreased gradually. The DSC results showed that a certain degree of gelatinization occurred in starch molecules during the first 25 s and 50 s of initial frying; the starch was completely gelatinized after 75 s and 100 s of initial frying, and an amylose-lipid complex was formed after 20 s of repeated frying. XRD indicated that after 75 s of initial frying, the degree of crystallinity of the starch was higher than that after 25 s of initial frying. After 40 s of repeated frying, the crystallinity of starch decreased with frying time.