油炸过程中淀粉的颗粒形貌、结晶度与热力学特性变化

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

采用深层油炸模型,利用扫描电镜分析、差示扫描量热分析和x-射线衍射分析等现代仪器分析方法,研究了油炸过程中淀粉的颗粒形貌、结晶结构和热力学性质的变化规律。SEM分析表明,随着油炸温度的增加和时间的延长,淀粉颗粒形态发生了明显变化。在初炸时,淀粉颗粒逐渐膨胀;随着复炸的进行,淀粉颗粒崩解,相互靠近,融合形成大块的团聚体。同时,也导致了淀粉的碘蓝值逐渐减少。DSC测定结果表明,当初炸25 s和50 s时,淀粉分子发生了一定程度的糊化作用;当初炸75 s和100 s时,淀粉完全糊化;当复炸超过20 s时,淀粉在油炸过程中形成了淀粉-脂质复合物。X-射线衍射分析显示,当初炸超过75 s后,淀粉的结晶度均高于初炸25 s淀粉的结晶度;复炸40 s后淀粉的结晶度随油炸时间的延长而降低。

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.