Frederick C. Felker

Distribution of Octenyl Succinate Groups in Octenyl Succinic Anhydride Modified Waxy Maize Starch

The location of octenyl succinate groups within octenyl succinic anhydride (OSA)-modified waxy maize (WM) starch granules was studied in order to better understand the relationship between the structure and physical properties of OSA starches. OSA starches of D.S. 0.03—0.11 were prepared by reaction between starch, OSA and NaOH in aqueous suspension; the native granular structure of starch was retained after reaction. Backscattered electron imaging of osmium-stained, sectioned OSA starch granules showed a uniform distribution of OSA groups over the cross-section of the granules. Anion-exchange chromatography of OSA starches solubilized in water showed that most of the amylopectin molecules contain some negative charge, suggesting that most of the starch granule is accessible to and reacts with OSA. However, after partial debranching with pullulanase, more of the resulting chains were neutral than would be expected on statistical grounds, suggesting heterogeneity in OSA substitution at the branch level. X-ray photoelectron spectroscopy suggested that the concentration of OSAgroups on the immediate surface of the OSA starch granules was about 3—4 times that of the bulk.

Formation of crystalline aggregates in slowly-cooled starch solutions prepared by steam jet cooking

Abstract Spherocrystalline particles were formed in dilute, jet cooked solutions of normal cornstarch, high amylose cornstarch, rice starch and wheat starch, when hot solutions were allowed to slowly cool in insulated Dewar flasks. Yields ranged from approximately 7 to 12%, and particles were composed largely of amylose. Spherocrystals were not obtained from waxy cornstarch, defatted cornstarch or potato starch. Normal cornstarch, high amylose cornstarch and rice starch yielded mixtures of two different particulate species, each having its own unique size and morphology. Both species were strongly birefringent, and no significant loss of birefringence was observed when particles produced from normal cornstarch were heated in water to 97–99°C. Scanning electron microscopy (SEM) showed that smaller-sized particles were disc or torus-shaped and often exhibited spiral surface striations. The larger particles were approximately spherical in shape, and had rough surface textures. Wheat starch yielded only a single spherical small-particle species. X-ray powder diffraction patterns of small particle material matched patterns previously reported for the 61 amylose V-helical complex in the hydrated form. In contrast, diffraction patterns for large particle material suggested the 71 V-helical conformation for amylose. These results are consistent with the theory that spherocrystalline particles result from crystallization of helical inclusion complexes formed from amylose and the native lipid material present in cereal starch granules.

Rheological Properties of Vital Wheat Gluten Suspensions

ABSTRACT Flour and doughs represent rheologically complex materials whose properties are dependent on many factors including processing conditions. To avoid some of the problems associated with the rheological characterization of dough, we have initiated a study focused on the rheological properties of one of the major components of dough, vital wheat gluten. Suspensions of vital wheat gluten were prepared with concentrations of 225–325 mg/mL.The moduli of the gluten suspensions was 0.2 Pa at 225 mg/mL to 37 Pa at 325 mg/mL. At 300 mg/mL, the gluten suspensions exhibited solidlike behavior. The crossover frequencies were independent of concentration and equal to 100 rad/sec. At 300 mg/mL, the high-frequency...

Ultrastructural studies on microencapsulated oil droplets in aqueous gels and dried films of a new starch-oil composite☆

Abstract Combination of starch, water, and oil by a process utilizing an excess-steam jet cooker produces a new class of stable, oil-in-water dispersions. Examination of aqueous gels by light microscopy (LM) and transmission electron microscopy (TEM) and of dried thin films by scanning electron microscopy (SEM) shows that the oil is microencapsulated in the starch water matrix or in the dried starch matrix as droplets that are typically 1–10 μm in diameter. The size and distribution of oil droplets in cornstarch-soybean oil composites are determined by a number of factors, such as oil:starch ratio, the number of times the formulation is passed through the steam jet cooker during preparation, and the steam pressure used during cooking. Oil droplet size can be reduced by addition of protein or starch-oil composites from a previous cook to the formulation prior to cooking. Oil droplet distribution in these composites is observable not only in scanning electron micrographs of fracture surfaces, but also by light microscopy and by transmission electron microscopy of aqueous gels. Micrographs suggest the presence of a boundary layer surrounding the oil droplets which prevents them from coalescing.

Shear-thickening and shear-induced pattern formation in starch solutions☆

Since Dintzis et al. reported shear-thickening behavior and shear-induced pattern formation in semidilute starch solutions for the first time in 1995, considerable efforts have been made to understand the science behind these observations. Despite these efforts, however, many questions regarding this behavior of starch solutions remain. Using a Brookfield programmable rheometer and a custom-built shear microscope, starch solutions in alkaline solution medium were investigated. In this report, we present data leading to the following conclusions: (1) gently prepared starch solutions are macroscopically heterogeneous with regions of highly concentrated gel-like structures dispersed in dilute starch solution; (2) shear breaks up these heterogeneous regions, increasing in viscosity (shear-thickening) which is thus seen to be a result of an increase in the concentration of dissolved starch; (3) pattern formation, observed when the solution is exposed to higher shear rate, is the result of a separate shear-induced aggregation process; and (4) aggregations are not induced below a certain critical threshold shear rate and time is also a factor in the behavior of the aggregate.

The putative glutamate receptor 3.2 from Arabidopsis thaliana (AtGLR3.2) is an integral membrane peptide that accumulates in rapidly growing tissues and persists in vascular-associated tissues

Abstract The accumulation and localization of the transcript and peptide corresponding to the gene that encodes the putative glutamate receptor isoenzyme 3.2 in Arabidopsis thaliana (AtGLR3.2) is reported. Polyclonal antibodies, raised to the C-terminal region of AtGLR3.2, were used to determine that the putative plant glutamate receptor is an integral membrane protein with an apparent molecular weight of 111±1 kDa. RNA blot analysis revealed temporal accumulation of the AtGLR3.2 transcript in developing seedlings, results that were confirmed by polymerase chain reaction with reverse transcriptase-polymerase chain reaction (RT-PCR). Accumulation of the AtGLR3.2 transcript was highest in rapidly dividing tissues. Immunoblot analysis established that the presence of the AtGLR3.2 peptide mirrored, in most cases, the accumulation of the AtGLR3.2 transcript and suggests that AtGLR3.2 peptide accumulation is controlled in part by gene expression or RNA turnover. Affinity purified antibodies were used to localize the AtGLR3.2 protein in thin tissue sections. Immunohistochemical staining was intense and generalized in the rapidly dividing tissues of the developing floral buds, but mostly confined to the vascular tissue of the more mature hypocotyl, leaf and floral shoot tissues. Localization of the AtGLR3.2 protein to the rapidly growing tissues and vascular tissues is consistent with its proposed role in the translocation of calcium.

Starch–paraffin wax compositions prepared by steam jet cooking. Examination of starch adsorbed at the paraffin–water interface ☆

Abstract Starch–paraffin wax compositions were prepared by passing aqueous two-phase mixtures of cornstarch and paraffin wax through a steam jet cooker under excess steam conditions. Jet cooking converts the paraffin wax to micron-sized droplets that remain suspended in the aqueous dispersion and do not coalesce, due to an adsorbed layer of interfacial starch that surrounds each droplet. Solidified droplets of starch-coated paraffin wax were isolated by dilution of jet cooked dispersions with excess water followed by centrifugation. Wax droplets, having specific gravity lower than that of water, were collected from the dispersion surface, washed with water, and dried. Weight percent interfacial starch in isolated wax droplets was calculated from the weight of residual starch remaining after removal of paraffin wax by extraction with cyclohexane. Starch percentages varied from about 3–8%, depending upon whether waxy, normal, or high amylose starch was used, and whether jet cooked dispersions were diluted with hot or cold water prior to centrifugation. The effect of small amounts of lipid material (normally present in cereal starches) on weight percent interfacial starch was determined by examining products prepared from starch that was solvent-extracted to remove the lipid component (i.e. defatted). Although defatted normal cornstarch produced a product having a lower percentage of interfacial starch than a comparable product prepared from starch that still contained native lipid, defatting had little effect when waxy starch was used. The morphology of the starch layer, as observed by SEM, was affected by the presence or absence of lipid in the starting starch. Amylose was preferentially adsorbed at the paraffin–water interface when native lipid was present in the starting starch, suggesting that lipid enhances the adsorption of amylose through the formation of helical inclusion complexes. X-ray diffraction patterns of interfacial starch were consistent with this interpretation and showed the V h -pattern commonly attributed to amylose–lipid complexes. Nitrogen analyses suggested that proteins, present in cornstarch in small amounts, may also adsorb along with starch at the paraffin–water interface.

Glycols in Polyurethane Foam Formulations with a Starch-Oil Composite

A dry starch-oil composite was blended with each of three glycols; ethylene, polyethylene, and propylene, and then reacted with isocyanate to produce polyurethane foams. The liquid glycols permitted the dry composite to blend well with the other ingredients in the foam formulations. Infrared spectra confirmed the presence of ure- thane structures in the composite-glycol foams. Polyethylene glycol provided a slightly less dense foam than the other glycols in the composite-glycol products. Microscopy showed a greater number of larger cells in the composite-polyurethane glycol foams. Infrared spectra indicated essentially no qualitative differences in the composite-glycol foams with the three glycols. By prestaining starch with toluidene blue and oil with sudan red, the location of the starch and oil components of the milled composite were observed in the composite-propylene glycol foam. Intact flakes of the composite were observed in the foam. An apparent loss of mobility of oil in the composite-polyurethane foam, as evidenced by NMR analysis, is probably due to crosslinking by isocyanate diffusing into the flakes. Both the cell structure and uniformity of blending were improved by using these glycols rather than the polyester polyol described previously. q 1998 John Wiley & Sons, Inc. ‡ J Appl Polym Sci 69: 957-964, 1998

Light Quality During Early Seedling Development Influences the Morphology and Bitter Taste Intensity of Mature Lettuce. (Lactuca sativa) Leaves

Summary The genetic constitution of a vegetable crop species such as lettuce. ( Lactuca sativa ) is an important determinant of characteristics such as leaf size, shape, texture, color, and taste. Whereas introduction of improved traits by breeding or genetic engineering is possible, an alternative approach involves modification of the mature phenotype by manipulation of the early growth environment. To explore this phenomenon, lettuce was grown under specific light quality treatments. (red, red + far-red, blue, and white light), both continuously and with color switching at various intervals. Leaves grown in continuous light quality showed characteristic differences in leaf area, shape, dry weight, and bitter taste intensity as determined by an analytical sensory panel. However, red light supplied for the first 7 d of growth conditioned weak bitterness intensity whether or not plants were switched to white light for 18 or 26 d. Leaf area and dry weight were determined by the first 7 d in red or blue light whether or not plants were switched to the opposite color light for 9 or 35 d. These observations demonstrate that persistent photomorphogenic switching of leaf development can take place before leaf emergence, and that light quality signals received in the early growth environment can have a latent effect on subsequent plant development.

Preparation of starch-stabilized silver nanoparticles from amylose–sodium palmitate inclusion complexes

Starch-stabilized silver nanoparticles (AgNP) were prepared from amylose-sodium palmitate helical inclusion complexes by first converting sodium palmitate within the amylose helix to silver palmitate by an ion-exchange reaction with silver nitrate, and then reducing the complexed silver palmitate salt with NaBH(4). This process yielded stable aqueous solutions that could be dried and then re-dispersed in water for end-use applications. Reaction products were characterized by inductively coupled plasma-atomic emission spectroscopy (ICP-AES), UV-VIS spectroscopy, X-ray diffraction, TEM, SEM and light microscopy. Addition of acid to reduce the pH of aqueous starch-AgNP solutions produced an increase in viscosity, and nearly quantitative precipitation of starch-AgNP was observed at low pH. Smaller AgNP and higher conversions of silver nitrate to water-soluble starch-AgNP were obtained in this process, as compared with a process carried out under similar conditions using a commercial soluble starch as a stabilizer.