Spherulitic crystallization of starch: influence of botanical origin and extent of thermal treatment

Numerous, well-developed spherulites exhibiting strong birefringence were formed in aqueous dispersions of mung bean and potato starch rapidly quenched (150 °C/min) from 180 °C. Ordinary maize starch yielded less numerous, less well-developed, coarse spherulites than did mung bean and potato starch. Acid-modified maize starch yielded large numbers of very round spherulites displaying moderately strong birefringence. Wheat, tapioca and arrowroot starches formed few or very poorly developed spherulites. No spherulitic morphology was observed in oat, rice, or sorghum starch dispersions. Equivocal results were obtained for amaranth and yellow pea starches. Potato and mung bean starches required heating to at least 170 °C before spherulite formation was observed. Acid-modified maize starch formed spherulites after heating to only 160 °C and possibly as low as 150 °C.