101 research outputs found
Starch analysis using hydrodynamic chromatography with a mixed-bed particle column
Columns packed with commercial glass beads 5 and 19 lm average size and a mixture of both (0.7 volume
fraction of large particles) were used to analyse starch composition by hydrodynamic chromatography
(HDC), applying water as mobile phase. To obviate retrogradation, experiments were carried out at
column temperatures of 15 and 3 °C and several types of starch were assayed. In what concerns amylopectin
and amylose separation, a better resolution and a lower pressure drop were obtained for the mixed
binary packing when compared with the packing containing uniform 5 lm glass beads. A more efficient
cooling of the mobile phase was also obtained with the mixed packing, which was determinant for
improving resolution. For the Hylon VII starch the relative retention times (RRT) were 0.777 and 0.964
for amylopectin and amylose, respectively, while for the Tapioca starch the obtained RRTs were 0.799
and 0.923. Application of unbound glass beads as column packing not only might reduce equipment
and running costs in preparative scale separations, but also proved to be useful as a fast and reliable
method to monitor the amylose and amylopectin content of starch samples of different sources.FEDERThe authors wish to thank FCT for the grant provided to Dr. Alexander Yelshin (Yelshyn). This work was developed under the framework of the project POCI-EQU-58337/2004, partially funded by FEDER
Developmental Localization and Methylesterification of Pectin Epitopes during Somatic Embryogenesis of Banana (Musa spp. AAA)
The plant cell walls play an important role in somatic embryogenesis and plant development. Pectins are major chemical components of primary cell walls while homogalacturonan (HG) is the most abundant pectin polysaccharide. Developmental regulation of HG methyl-esterification degree is important for cell adhesion, division and expansion, and in general for proper organ and plant development.Developmental localization of pectic homogalacturonan (HG) epitopes and the (1→4)-β-D-galactan epitope of rhamnogalacturonan I (RG-I) and degree of pectin methyl-esterification (DM) were studied during somatic embryogenesis of banana (Musa spp. AAA). Histological analysis documented all major developmental stages including embryogenic cells (ECs), pre-globular, globular, pear-shaped and cotyledonary somatic embryos. Histochemical staining of extracellularly secreted pectins with ruthenium red showed the most intense staining at the surface of pre-globular, globular and pear-shaped somatic embryos. Biochemical analysis revealed developmental regulation of galacturonic acid content and DM in diverse embryogenic stages. Immunodots and immunolabeling on tissue sections revealed developmental regulation of highly methyl-esterified HG epitopes recognized by JIM7 and LM20 antibodies during somatic embryogenesis. Cell walls of pre-globular/globular and late-stage embryos contained both low methyl-esterified HG epitopes as well as partially and highly methyl-esterified ones. Extracellular matrix which covered surface of early developing embryos contained pectin epitopes recognized by 2F4, LM18, JIM5, JIM7 and LM5 antibodies. De-esterification of cell wall pectins by NaOH caused a decrease or an elimination of immunolabeling in the case of highly methyl-esterified HG epitopes. However, immunolabeling of some low methyl-esterified epitopes appeared stronger after this base treatment.These data suggest that both low- and highly-methyl-esterified HG epitopes are developmentally regulated in diverse embryogenic stages during somatic embryogenesis. This study provides new information about pectin composition, HG methyl-esterification and developmental localization of pectin epitopes during somatic embryogenesis of banana
Effect of calcium ions and pH on the structure and rheology of carrot-derived suspensions
Pectin methylesterase activity determined by different methods and thermal inactivation of exogenous pme in mango juice
Effects of High Pressure and Heat Treatment on Pectic Substances and Related Characteristics in Guava Juice
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