Cereal Chem 65:474-483   |  VIEW ARTICLE

Paste and Gel Properties of Prime Corn and Wheat Starches With and Without Native Lipids.

S. Takahashi and P. A. Seib. Copyright 1988 by the American Association of Cereal Chemists, Inc. 

Corn starch showed higher fresh paste consistency than wheat starch, and, after aging 24 hr, its gels were more firm at 6% solids or less. Between 7 and 30% solids, gels of wheat starch were more firm than those of corn starch. The lipids in wheat and corn starches were reduced 88-97% by boiling three times in four parts of a 3:1 (v/v) mixture of ethanol/water. Iodine-binding capacity of corn and wheat starches was highest after extraction with 75% n-propanol at 100 C compared to other solvents. Soxhlet extraction with methanol removed 93% lipid from corn starch, but only 78% from wheat starch as judged by iodine-binding capacity; hot 75% ethanol removed 97% lipid from wheat starch, but only 88% from corn starch. Amylograms of the low-lipid starches in 1% carboxymethylcellulose showed an initial, rapid increase in consistency as temperature rose 10 C beyond gelatinization. Then, consistency increased slowly and steadily up to 95 C. This initial rapid increase coincided with the rapid release of amylose into the soluble phase of the paste. Amylograms of the low-lipid starches in water showed a decrease in pasting temperature, no pasting peak, and reduced consistency and setback. When prime wheat starch was impregnated with 2% wheat starch lipids, the pasting peak and consistency in the amylograph increased, and a strong second peak was observed during the cooling cycle. When the same amount of wheat starch lipid was added to the starch paste after it reached 95 C in the amylograph, the peak during the cooling cycle was markedly reduced, as was setback. Setback was not observed at 2% added lipids. Wheat lipids decreased gel strength and syneresis somewhat during storage at 4 C, but they did not affect syneresis during freeze-thaw treatment.