Xerophytic Gourd Root Starches. Part V: Structural Characteristics, Gelatinization Properties and Rheologic Behavior of Coyote Gourd Starch ( Cucurbita digitata Gray)

As part of a continuing study of xerophytic cucurbit starches, coyote gourd ( Cucurbita digitata Gray) root starch and starch components have been examined. Coyote gourd amylose and amylopectin fractions were highly susceptible to β‐amylolysis; average degree of polymerization and average unit chain lengths of the latter material intimated the large size and multiply‐branched asymmetrical structure of the molecules. The isolated granules were small, spherical or irregular in shape and birefringent. Crystalline regions of native granules evinced a B‐type diffraction pattern which was altered to that of the C‐type by treatment with moist heat. Gelatinization characteristics, restricted swelling and low solubility of the subject material suggested a highly organized granule architecture. Gelatinized suspensions formed stiff opaque gels upon cooling which were resistant to deformation. A strong degree of association among granule components was also evident in the rheologic behavior of the material. In general, the effects of suspension concentration, acidity and sucrose upon the rheologic performance of this material were predictable from known behavior of standard starches; the addition of salt or oil resulted in increased pasting temperatures and had variable influence upon suspension viscosities.