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Starch granule morphology differs markedly among plant species. However, the mechanisms controlling starch granule morphology have not been elucidated. Rice (Oryza sativa) endosperm produces characteristic compound-type granules containing dozens of polyhedral starch granules within an amyloplast. Some other cereal species produce simple-type granules, in which only one starch granule is present per amyloplast. A double mutant rice deficient in the starch synthase (SS) genes SSIIIa and SSIVb (ss3a ss4b) produced spherical starch granules, whereas the parental single mutants produced polyhedral starch granules similar to the wild type. The ss3a ss4b amyloplasts contained compound-type starch granules during early developmental stages, and spherical granules were separated from each other during subsequent amyloplast development and seed dehydration. Analysis of glucan chain length distribution identified overlapping roles for SSIIIa and SSIVb in amylopectin chain synthesis, with a degree of polymerization of 42 or greater. Confocal fluorescence microscopy and immunoelectron microscopy of wild-type developing rice seeds revealed that the majority of SSIVb was localized between starch granules. Therefore, we propose that SSIIIa and SSIVb have crucial roles in determining starch granule morphology and in maintaining the amyloplast envelope structure. We present a model of spherical starch granule production. [ABSTRACT FROM AUTHOR]

Alternative forms of protein are an important focus in nutrition. This study sought to compare the effects of pelleting and extrusion on nutrient composition and protein quality measurements of Canadian pulses. Pulses used for the study included: 2 pea variety (Amarillo and dunn), lentils, chickpeas, and faba bean. Ingredients were ground through a 10/64" or a 2/64" screen to create a coarse and fine ground product, respectively. Both coarse and fine ground ingredients were pelleted at 60-65, 70-75, and 80-85 C0. Fine ground ingredients were extruded at three different temperatures (110, 130, 150 C0) and two moisture levels (18 and 22%). Samples were collected for all runs at the beginning, middle, and end of each run for both pelleted and extruded samples. Samples were analyzed for proximate analysis, amino acids including lysinoalanine, total and damaged starch, and total dietary fibre (including insoluble and soluble). Data were analyzed using a mixed model via proc glimmix in SAS, where ingredient, process, grind, temperature, and extrusion moisture were treated as fixed effects with different interactions selected based on model investigated. Crude protein content of whole pulses was highest in faba bean and lowest in the Amarillo pea, with faba bean protein content significantly higher than all other pulses, and lentil protein content significantly higher than Amarillo peas (P < 0.05). All pelleting temperatures, nested within grind, significantly increased crude protein content of all pulses compared to whole pulses (P < 0.05). All extrusion moistures significantly increased crude protein content of all pulses compared to whole pulses (P < 0.05) and moisture/temperature interactions were significantly higher for all pulses compared to whole pulses (P < 0.05). Amino acid comparisons produced similar significant results. This suggests that pelleting and extrusion processing can have a positive impact on protein content of pulses and protein quality measurements in pulses. [ABSTRACT FROM AUTHOR]