Preparation of spherulites from amylose–palmitic acid complexes

We conducted a systematic study of the formation of spherulites from amylose–palmitic acid complexes. The independent variables included final heating temperature, intermediate quench temperature, final quench temperature and cooling rates. Spherulites were characterized by different techniques: optical microscopy, scanning electron microscopy, differential scanning calorimetry, X-ray diffraction, transmission electron microscopy and resistant starch content. Three distinct types of spherulite morphology were observed: spherical, sintered (“snowball”) and torus/disc shaped. Spherical-shaped particles were formed at higher endpoint heating temperatures and exhibited mixed B+V-type XRD patterns. Torus-shaped spherulites formed from samples heated to 140 °C followed by slow cooling, and exhibited V-6I type XRD patterns. Resistant starch estimated for spherulites formed by heating to 180 °C followed by cooling to 40 °C at 1 °C/min vs. those formed by heating to 140 °C, cooled to 90 °C at 1 °C/min then to 40 °C at 0.04 °C/min was 28% and 39%, respectively. Morphology of the amylose–PA spherulites after resistant starch determination for spherical spherulite shows distinct pores and uneven surface texture. In contrast, the torus-shaped spherulites were degraded with evidence of recrystallization.