Crystalline particles formed in slowly-cooled cornstarch dispersions prepared by steam jet cooking. The effect of starch concentration, added oil and rate of cooling

Abstract

Spherical/lobed and torus-shaped particles were formed when jet cooked cornstarch dispersions (4–10% starch solids) were slowly cooled for 22 h. When jet cooking was carried out in the presence of mineral oil, the torus-shaped particles did not form, but small spherical particles, about 1–2 μm in diameter, were observed. These small particles resembled those formed in wheat starch dispersions jet cooked in the absence of oil. Dispersions jet cooked without oil and cooled over a 4 h period also yielded 1–2 μm spheres in addition to the spherical/lobed and torus-shaped particles. With 4 h cooling in the presence of oil, the torus-shaped particles were absent, and the 1–2 μm spheres were the only small particles observed. Very few spherical/lobed particles were formed in the presence of oil at starch concentrations of 5 and 4%. Mineral oil droplets could affect the nature of the particles formed by selectively extracting free fatty acids from the native lipid released from cornstarch by steam jet cooking. The remaining native lipid would therefore be richer in lysophospholipids, thus favoring the formation of 1–2 μm spheres, similar to those observed with wheat starch. The rate of cooling could affect the nature of the particles formed because of its effect upon the depletion of native lipid components from the dispersion by the particles that form first at the highest temperature.