311 Characteristics of starches modified using liquid ammonia and ethanol.

R. JACKOWSKI, Z. Czuchajowska, and B.-K. Baik. Department of Food Science and Human Nutrition, Washington State University, Pullman, WA 99164-6376.

Starches isolated from wheat, corn, smooth and wrinkled peas and garbanzo beans were modified using liquid ammonia and ethanol at low temperature and atmospheric pressure to produce a free-flowing powder of granular cold water gelling (GCWG) starch. Changes in molecular structure, enzyme digestibility, swelling and gelling properties and retrogradation characteristics of GCWG starches were determined and compared to the native starches. The molecular distribution patterns of amylose and amylopectin, determined using size exclusion chromatography, were similar between modified and native starches, indicating that the modification process did not alter the fine structure of the molecular composition. With enzymatic hydrolysis, GCWG starches exhibited higher dextrose equivalent (DE) values than both native and pregelatinized starches, suggesting that the modification process altered the crystalline integrity within the starch granules, allowing for easy enzyme accessibility. Modified starches formed weak gels without heat treatment and had no change in gel hardness during storage in wheat, corn, smooth peas and garbanzo beans, while native starches required heat treatment to form gels and showed an increase in gel hardness from 1.0 N to 6.4 N over 96 hr. Swelling power of modified starches from wheat, corn, smooth peas and garbanzo beans at 23 C ranged from 9 g/g to 16 g/g, while swelling power of native starches at 92.5 C ranged from 14 g/g to 17 g/g. Modified wrinkled pea starch exhibited a swelling power value of 15 g/g, whereas the swelling power of native wrinkled pea starch was 5 g/g.