POLARIMETRIC DETERMINATION OF STARCH IN CEREAL PRODUCTS: III. COMPOSITION AND SPECIFIC ROTATORY POWER OF STARCHES IN RELATION TO SOURCE AND TYPE

Abstract

Under the conditions of an improved calcium chloride procedure, only very small differences in specific rotation value have been observed between samples of starch obtained from the same species or genus, nine wheat starches representing hard, soft, and durum varieties grown at different stations varying only from 202.3° to 203.2°. The specific rotation values for 48 samples of starch representing 20 different genera or species also showed little divergence from 203. Average values for wheat starch were 202.7; corn, 202.9; waxy corn, 202.3; barley, 203.5; waxy barley, 202.5; rye, 202.8; oat, 202.9; rice, 203.0; waxy rice, 202.7; grain sorghum, 203.2; waxy sorghum, 202.3; buckwheat, 203.4; millet (impure), 201.4; sweet potato, 203.4; arrowroot, 203.3; tapioca, 202.8; potato, 204.1; lily (bulb), 203.9; pea, 199.4; and bean, 200.4. Storage of starch for upwards of 10 years caused a decrease in the specific rotation value.The fat content of the waxy starches was consistently lower than that of the corresponding non-waxy cereal starches. Oat starches had by far the highest fat content, averaging 1.2%. The fat content of legume, bulb, root, and tuber starches was low but measurable. The protein content of the root, bulb, and tuber starches was approximately 0.1%, and of commercial rice, 0.5%, all of the remaining starches with the exception of the impure millet being intermediate in this respect.