Physical and Molecular Characterization of Millet Starches

Abstract

Cereal Chem. 91(3):286-292This study investigated the physical and molecular starch characteristics of four Canadian-grown millet species: pearl, foxtail, proso, and finger millet. The millet starch granules ranged from about 2.5 to 24 μm in size and were mainly polygonal with a few spherical ones. Their amylose contents ranged from 28.6 to 33.9%, with finger and pearl millets having much more of long amylose chains than short amylose chains compared with foxtail and proso millets. Starches also differed in the molecular structure of their branched amylose, with finger and pearl millets having longer glucan chains between branch points. The enthalpy of gelatinization of starch granules ranged from 11.8 to 13.2 J/g, and the enthalpy of melting of the retrograded starches ranged from 2.2 to 5.9 J/g. The onset temperature of gelatinization (T o ) of the starches ranged from 62.8 to 70.6°C. Addition of iodine vapor to the granular starches showed significant (P < 0.05) differences in the ratio of the absorbance to scattering coefficient (K/S) values, indicating differences in the rigidity of the glucan chains present in the granules. Starches with short amylose chains exhibited higher K/S values. Iodine vapor addition resulted in altered X-ray diffractogram peak intensities. The study suggested differences in the structure and granular architecture of the millet starches.

Molecular and thermal characterization of starches isolated from African rice (Oryza glaberrima)

“…l max values were only slightly reduced after b-amylolysis and showed that the internal chains of rice AP also interacted with iodine. Similar results were obtained with AP from wheat [14], millet [33], maize [34], and potato [35] starches. However, similar or even higher l max values were observed in the AP region for the b-LDs from NERICA 4, Koshihikari, and WITA 4.…”

“…A higher LC AM : SC AM ratio indicates higher amount of long chains of amylose while a lower LC AM :SC AM ratio indicates higher amount of short chains of amylose. The LC AM :SC AM ratio in this study was largely found to be similar to foxtail and proso millet starches but lower than pearl and finger millet starches [33]. Gel-permeation chromatograms of rice starches and their corresponding b-limit dextrins (b-LDs) fractionated on Sepharose CL-2B along with their l max values are shown in Fig.…”

Starch hydrolysis kinetics of intermediate wheatgrass (Thinopyrum intermedium) flour and its effects on the unit chain profile of its resistant starch fraction

“…The average chain lengths of the resistant starch fractions ranged from 4.75 to 7.47. These values were significantly less than that average values of 17–18 reported for amylopectins from millet, rice, maize, and potato (Annor, Marcone, Bertoft, & Seetharaman, ; Bertoft, ,). The significantly shorter average unit chains of the resistant starch fractions were consistent with the fact that they were hydrolyzed by the starch degrading enzymes.…”

Effect of growing location and variety on nutritional and functional properties of proso millet (Panicum miliaceum) grown as a double crop

“…Previously reported amylose contents for proso millet starches span a relatively wide range with some studies reporting values ranging from ca. 27%–34% of total starch (Annor, Marcone, Bertoft, & Seetharaman, ; Zhang et al., ), and others reporting less than 20% of total starch (Kumari & Thayumanavan, ; Wen, Liu, Meng, Zhang, & Zhao, ). White proso, Sunrise from both locations, and Dawn from Waseca had the highest amylose contents, which were significantly different from those of most other varieties.…”