Dilute Starch Research Articles

Alkali-assisted hydrothermal route to control submicron-sized nanoporous carbon spheres with uniform distribution

Carbon microspheres with nanoporous structures were synthesized based on hydrothermal reaction of saccharide solutions in the presence of potassium hydroxide. The influence of synthesis conditions, including types of saccharide, content of alkali, concentration and reaction time of saccharide solution, on the morphology of the microspheres was systematically investigated, with emphasis on controlling the microsphere size and understanding the role of alkali in hydrothermal reaction. The results show that the microspheres with regular spherical shapes and high surface areas around 500m2g−1 are obtained. The morphology of the microspheres can be tailored by changing the synthesis conditions. The mean diameter of the microspheres varies from 0.16 to 5.61μm. At different stages of the hydrothermal reaction of starch solution, alkali exhibits entirely different effects: (i) to slow the initial hydrolysis of starch, and (ii) to accelerate the subsequent polymerization of dehydrated and fragmented products and the growth of the microspheres. As a result, the competition between the hydrolysis kinetics and the polymerization and growth kinetics plays a critical role in the changes of the morphology and yield of the microspheres. The alkali in dilute starch solution (0.073–0.219M) promotes the increase of the size and yield of the microspheres. In contrast, the alkali in concentrated starch solution (0.292M) results in the reduction and the more uniform distribution of the size of the microspheres with almost constant yield. Note that this alkali assisted hydrothermal route can endow the microspheres with more surface functional groups, including hydroxyl and carboxyl groups, compared with the typical hydrothermal route without alkali. In addition, the formation of the stacks of graphene sheets and the decrease of functional groups occur in the microspheres during pyrolysis, which are accompanied by a significant weight loss of about 50% and a slight contraction in scale.

Shear-induced aggregate formation in starch solutions

Shear-thickening behavior and shear-induced pattern formation have been observed in semidilute starch solutions. While the shear-thickening behavior is due to breaking up of highly concentrated gel-like structures dispersed in dilute starch solutions, the pattern-forming behavior is not well understood. The pattern formation, observed when the starch solution is exposed to a high shear field, is a consequence of shear-induced aggregation and is not related to shear-thickening behavior. The patterns have been observed above a certain critical threshold shear rate regardless of the starch type. In this report, it is shown that the product of shear time and fourth power of shear rate is a controlling factor for the formation of shear-induced aggregates in starch solutions. Since starch solutions prepared under harsh conditions did not show shear-induced aggregate formation, it is suggested that the aggregates are formed from incompletely solubilized starch residues in its apparent solution.

A Small-scale Spectrophotometric Method for Determining Starch Gelatinisation

The development of a small-scale spectrophotometric method of determining both onset and peak gelatinisation temperatures of starch is reported. In this assay the changes in absorbance of a dilute starch suspension are measured at 380 nm as the suspension is heated to 95°C. The values obtained from this method for both onset and peak gelatinisation temperatures correlate extremely well with those obtained by DSC, but are generally 5°C to 10°C lower. This method works on both pure and crude starch samples and thus has the potential to be used in a high-throughput format allowing up to 100 samples per day, making it useful for research and breeding programs in which large numbers of impure starch samples need to be assayed. This allows for earlier selection of the lines of interest, which can then be analysed more comprehensively with techniques such as DSC which provide a greater amount of information, thus saving the researchers' time and money.

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.

Mechanical mixing and biological deactivation: the role of shear stress application time

The macroscopic effects of mechanical mixing on the biological activities of Saccharomyces cerevisiae cells employed in batch fermentations of dilute starch hydrolysate solutions are studied. The rotational speed strongly affects the overall product yield over 300 min −1. Also the fermentation kinetics is markedly influenced by agitation intensity, in that the process appears to be limited by substrate diffusion from the bulk to the cell inside up to 450 min −1, whereas cell metabolism becomes of greater significance over this threshold. A new model is also presented to describe the decrease in specific productivity with the increase in either the mixing intensity or the exposure time to shear stress. The present results suggest the existence of different types of simultaneous mechanisms for metabolic activity inhibition and/or death linked to mechanical mixing.

Rats discriminate between starch and other substances having a similar texture

Studies examined the contribution of textural factors to the ability of rats to sense starch. If rats sense the abrasive effects of starch suspensions, conditioned aversions to starch should generalize to substances having a similar texture. Two substances having a texture similar to that of starch were examined, polymeric dialdehyde (a product derived from starch) and inulin (a polymer of fructose). Rats were trained to avoid dilute suspensions of rice starch, potato starch, polymeric dialdehyde, or dahlia inulin, by injecting them with lithium chloride after they drank the test substance. Generalization tests revealed that rats trained to avoid rice or potato starch subsequently avoided corn starch, whereas rats trained to avoid polymeric dialdehyde or dahlia inulin did not avoid corn starch. Rats trained to avoid polymeric dialdehyde avoided this substance to a greater degree than did rats trained to avoid rice or potato starch. Rats trained to avoid dahlia inulin avoided this substance to a greater degree than did the rats in the other groups, but avoidance of dahlia inulin did not generalize to chicory inulin. Untrained rats showed little or no preference for dilute suspensions of polymeric dialdehyde or inulin, but did prefer starch over vehicle. It is concluded that tactile sensitivity does not play a large role in the perception of dilute starch suspensions.

Foam Fractionation of Proteins: Potential for Separations from Dilute Starch Suspensions

AbstractFundamentals of the separation of proteins from foam are reviewed. Thermodynamic, hydrodynamics and kinetic considerations of foam separation from protein mixtures are discussed as a guidance for operating and design parameters. They are useful for suggesting ways to apply this methodology to the starch industry. particularly in the area of protein (zein) removal from starch particles.

Acquired sensory control of satiation in man.

Lean male and female subjects who had been taking their meals as usual were given a 100 ml drink of starch immediately before a sandwich lunch. In the training phase,65 per cent starch was given before lunches which included a yoghurt-based dessert of one flavour and 5 per cent starch was given before another flavour. Subjects who initially ate lunches of similar size following the two drinks began after several pairings to take larger lunches following dilute starch than following concentrated starch. In extinction tests, identical 35 per cent starch drinks were given before lunches including desserts of either flavour. Lunches including the flavour hitherto paired with dilute starch remained larger than lunches including the other flavour, at least initially in extinction. Some of the difference in intake occurred in the dessert itself. None was attributable to differences in the early stage of the lunches. These results extend to man recent demonstrations that the satisfying power of a foodstuff is in part acquired by association of its sensory characteristics with some consequence of ingesting the nutrients which are consistently taken with or in that food. This consequence may be rapid intestinal absorption of glucose during or shortly after sensory input. The nature of the intake-suppressing response remains to be determined.

Gastrointestinal factors in the acquisition of oral sensory control of satiation

Rats were given a series of starch meals. Half the meals were of a 65% starch solution with one taste added and the other meals were 5% carbohydrate which had been given another taste. After a few meals of each type, the dilute starch began to be taken in larger volumes. The rats were then given test meals of 35% starch having either flavour. The rate of intake towards the end of a meal decelerated more slowly in the presence of the taste given to dilute starch than in the presence of the flavour given to concentrated starch. The taste of dilute starch was not systematically preferred in a two-stimulus test. Thus there was a conditioned differentiation of the oral control of satiation: the onset of satiety was slowed in the presence of oral cues which had been associated with the passage of very little carbohydrate. The oral control of satiety was acquired even when meals differed in starch concentration during their first 5 min only. In contrast, concentration differences after the first 5 min did not generate an adequate unconditioned stimulus. It appeared therefore that the unconditioned stimulus was related to the phase of rapid starch clearance and glucose absorption which occurs early in the meal. This conclusion was supported by the additional finding that rats conditioned faster after bilateral subdiaphragmatic vagotomy, when fat-free diets are cleared faster than in intact rats. This result also indicated that the conditioned oral stimuli did not reduce the satiating power of ingested nutrients via motor control of the stomach or by interacting with vagal afferent information.

Small‐angle light scattering from optically anisotropic spheres and disks. Theory and experimental verification

AbstractThe small‐angle light scattering (SALS) theory for optically anisotropic spheres and disks is examined in depth. An error is found in the existing sphere equations. The correct form of the equations is identified and then experimentally verified for dilute starch suspensions. Increased concentrations and solid films of starch granules are used to identify the effect of concentration on the scattering envelope. Spherulitic films of isotactic polypropylene, isotactic polystyrene, nylon 610, PET, and nylon 66 are then used to examine different aspects of the SALS theory. Experimental observations are found to agree with the predictions of the correct SALS equations. Disk theory is interrogated and correlated with predictions for spheres. It is found that the predicted patterns from spheres and disks are very similar under identical optical conditions, in contradiction to earlier predictions. A method is developed for identifying the optical sign of spherulites too small to be seen in the optical microscope. This study constitutes a comprehensive examination of SALS theory and includes many other aspects of the phenomena. A catalogue of theoretical Vv SALS patterns from spheres and disks is also included.

Some Data on Mechanism of Leukopenia and Leukocytosis Following Irradiation

Abstract1. In rabbits irradiated with 150 to 600 r, granulocytosis is preceded by a prompt significant granulocytopenia developing 5-15 minutes after irradiation but persisting for a short time.2. The plasma taken at the minimum of the initial granulocytopenia produced a similar two-phase reaction when injected into normal animals: a promptly developing significant granulocytopenia persisting for a short period followed by prolonged granulocytosis. Prolonged thrombocytopenia might be induced by the very same plasma.3. The above-mentioned reactions may he reproduced satisfactorily with the administration of dilute starch solutions.4. On the basis of the results obtained, it seems likely that the agent demonstrable in the plasma after irradiation, and influencing the level of circulating granulocytes and thrombocytes, is not a toxin (leukotoxin) but a substance that may be formed following physiologic stimuli as well.

澱粉溶液静脈内注入ニ関スル実験的研究

Infusing Ringer-Locke's solution containing 1, 2, 4 or 6% soluble starch into the vein of rabbits with various velocities from ca. 1 to 10 cc. per kilogram per minute until they died, the author obtained the following facts : The greater the starch concentration in the solution infused, the more injuriously acts the infusion upon the animal body, that is, the smaller become the infusion quantities fatal to rabbits. With decrease of the infusion velocity, animals can endure a longer infusion, but the fatal infusion quantities are not increased every time. The total amount of the urine which is excreted during the infusion becomes smaller with the increase of the starch content. In the infusion of a Ringer-Locke's solution which contains 4 or 6 % starch with an infusion rate of less than 5 cc. per kilogram per minute, a slight rise of the blood pressure is always observed. The descended pressure due to bleeding ascends soon after the infusion of this fluid to a height almost equal to that of the initial pressure. But if the infusion is discontinued, it gradually descends again sooner or later. In the continual infusion, however, the blood pressure maintains its good condition till just before death. The pulse and the respiration show usualy no marked changes due to the infusion of starch solutions. On dissecting the animals after death, the changes in the thoracic organs are very marked. In the lungs are found oedema, stagnation and haemorrhages. The heart is always stopped in a diastolic state. The changes in the abdomen are, in general, slight. But in the slow infusion with a dilute starch solution when animals can stand a long infusion, they become striking. The stagnation and swelling of the liver, kidneys and other organs and abundant fluid in the intestine and transudate in the peritoneal cavity are then observed.