Whayman and co-workers1-3 studied starch isolated from varieties of cane grown in Queensland and from raw sugar. They related its properties to other starches and determined its influence on milling technology. Cane starch occurs in irregular granules which vary from 1 to 5 pm in maximum diameter, and has an amylose content of 14 +l% when measured on starches sampled throughout the cane-growing regions of the state. The amylopectin fraction absorbs less iodine in its complex than amylopectins from potato and waxy maize, and A,,, is at a lower wavelength. These properties were attributed to a higher degree of branching in the cane amylopectin.
Our studies were primarily to verify this hypothesis on the structural character of cane amylopectin. Amylolysis of starch isolated from raw sugar frequently indicates a residual component resistant to enzymic degradation but large enough to absorb iodine, as in the calorimetric method for starch analysis4. Our secondary objective was to determine whether amylase-resistant macrodextrins were produced during amylolysis of cane starch.
Amylopectins were prepared from starch recovered from cane variety NC0310 and potatoes grown locally. Amylopectin from waxy maize was purchased from ICN Pharmaceuticals (Cleveland, Ohio). Amylose was removed by complexing with 1-butanol, using the method of Schoch5. A second treatment of the amylopectin fractions with 1-butanol ensured no carry-over of amylose. Failure of the cane amylopectin to form a complex with 2-nitropropane confirmed the absence of an intermediate fraction6. The amylopectins were considered to be free of amylose, using the criteria of repeated treatment with butanol and similar spectral properties to those reported by Whayman and Willersdorfz.
Properties of average chain-length, light absorption by the iodine complex, and beta-amylolysis limit are shown in Table I.
Average chain-lengths were determined by periodate oxidation and IHn.m.r. spectroscopy. The amount of formic acid produced was the basis of the