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At least 1,621 records · Page 90Linked to original sources
PubMed2006

Sensory correlation of glucose levels in a starch-based semi-solid model system before and after alpha-amylase breakdown.

In this study a diabetic glucose monitor was used to measure the glucose content of 40 model vanilla custard desserts, these were compared with sensory ratings from a trained quantitative descriptive analysis panel. Stimuli varied in starch type, concentration and homogenisation but had identical sugar, flavour and fat contents. Despite this, mean sensory ratings of sweetness varied from 21 to 43 on a 100-point scale. Glucose levels in the stimuli were measured, in vitro, before and after the addition of 0.1% whole human saliva to the product. In all cases glucose concentration increased after the addition of saliva as starch was converted to glucose. There were highly significant correlations of some odour, flavour, mouth feel and after-feel attributes with glucose concentration. The correlation of sweet flavour with glucose concentration was higher in unmodified stimuli than in stimuli with added saliva, suggesting that sweetness is perceived soon after ingestion. Additional glucose produced through starch breakdown appeared to have a relatively small impact on the sensory scores of the stimuli.

Adult↗
PubMed2005

Comparison of hydroxyethyl starch and ringer lactate as a prime solution regarding S-100beta protein levels and informative cognitive tests in cerebral injury.

BACKGROUND: Cognitive dysfunction (as an indicator of cerebral dysfunction after open heart surgery) was observed in as many as 70% of patients who underwent cardiopulmonary bypass. S-100beta protein is a sensitive indicator of cerebral injury. We aimed to compare the effects of hydroxyethyl starch and Ringer lactate prime solutions in the protection of cerebral tissue in cardiopulmonary bypass using serum S-100beta protein levels and informative cognitive tests. METHODS: Patients were randomized into two groups. Open heart surgery was performed by using hydroxyethyl starch solution in group 1 (n = 15) and Ringer lactate solution in group 2 (n = 15). Preoperative, perioperative, and postoperative S-100beta protein levels and informative cognitive test scores, clinical and operational characteristics of the patients were compared. RESULTS: A significant difference was found only between preoperative and postoperative results of verbal accuracy (human) test in group 1, whereas differences between preoperative and postoperative scores of continuous skill, verbal accuracy (human), verbal accuracy (animal), verbal accuracy (human-animal), go-no-go paradigm, calculation, and abstract thinking tests were significant in group 2 (p < or = 0.05). The S-100beta protein levels were not significantly different between the groups (group p = 0.97). CONCLUSIONS: Because hydroxyethyl starch prime solution used in extracorporeal circulation had significant positive effects with informative-cognitive tests when compared to Ringer lactate solution, it seems to be a better prime solution to prevent cerebral dysfunction in these patients.

Cardiopulmonary Bypass↗
PubMed2004

Engineering a bifunctional starch-cellulose cross-bridge protein.

Biodegradable starch- and cellulose-based polymers have a range of properties which make them suitable for use in a wide array of biomedical applications ranging from bone replacement to engineering of tissue scaffolds and drug delivery systems. A novel polysaccharide cross-bridging protein was designed which was comprised of a cellulose-binding domain from Clostridium cellulovorans (CBD(clos)) and a starch-binding domain from Aspergillus niger B1 (SBD(Asp)). The two genes were fused in-frame via a synthetic elastin gene to construct a Cellulose/Starch Cross bridging Protein (CSCP). Recombinant CSCP was expressed in Escherichia coli, and successfully refolded from inclusion bodies. CSCP demonstrated cross-bridging ability in different model systems composed of insoluble or soluble starch and cellulose. The aspect that different carbohydrate-binding module maintain their binding capacity over a wide range of conditions, without the need for chemical reactions, makes them attractive domains for designing new classes of chimeric polysaccharide-binding domains which demonstrate potential for use in a wide range of biomaterials.

Aspergillus niger↗
PubMed2004

Structural parameters of amylopectin clusters and semi-crystalline growth rings in wheat starches with different amylose content.

Small-angle X-ray scattering (SAXS) and scanning electron microscopy (SEM) were used to investigate the internal structure of wheat starch granules with different amylose content. Different approaches were used for treatment (interpretation) of SAXS data to assess the values of structural parameters of amylopectin clusters and the size of crystalline and amorphous lamella in different wheat starches. The average values of the semi-crystalline growth rings thickness in starches have been determined and the relationship between structural characteristics and thermodynamic melting parameters is discussed.

Amylopectin↗
PubMed2006

A novel one-pot 'green' synthesis of stable silver nanoparticles using soluble starch.

Stable silver nanoparticles have been synthesized by using soluble starch as both the reducing and stabilizing agents; this reaction was carried out in an autoclave at 15 psi, 121 degrees C for 5 min. Nanoparticles thus prepared are found to be stable in aqueous solution over a period of three months at room temperature (approximately 25 degrees C). The size of these nanoparticles was found to be in the range of 10-34 nm as analyzed using transmission electron micrographs. The X-ray diffraction analysis revealed the face-centred cubic (fcc) geometry of silver nanoparticles. Iodometric titration confirmed the entrapment of silver nanoparticles inside the helical amylose chain. These silver nanoparticles embedded in soluble starch produced a typical emission peak at 553 nm when excited at 380 nm. The use of environmentally benign and renewable materials like soluble starch offers numerous benefits of eco-friendliness and compatibility for pharmaceutical and biomedical applications.

Amylose↗
PubMed2005

Water sorption-desorption behaviour of methyl methacrylate-starch copolymers: effect of hydrophobic graft and drying method.

A new family of graft copolymers combining hydrophilic and hydrophobic components have recently been proposed as direct compression excipients. Copolymers were synthetised by free radical copolymerisation of starch derivatives with methyl methacrylate (MMA) and were alternatively dried by oven or freeze-drying techniques. The aim of this study was to investigate the water vapour sorption-desorption behaviour of these copolymers, focusing on the influence of variables such as the hydrophobic component and the drying process. Moisture sorption and desorption isotherms were measured at 25 degrees C and analysed according to GAB and Young-Nelson equations, which distinguish between different physical forms of moisture distribution. The Young-Nelson model gave the best fit to the experimental data. The results obtained showed that the presence of the acrylic component modified not only the total hygroscopicity of the copolymers, as compared with the original starch derivatives, but also the water distribution in the solid, which might have an important role in the effect of moisture content on copolymer characteristics. The main water-sorption mechanism seemed to be absorption into the copolymer particles structure, in agreement with their starching nature. In terms of water sorption-desorption characteristics, no marked differences were found between the two drying methods used.

Desiccation↗
PubMed2005

Characterization and in vivo evaluation of ocular minitablets prepared with different bioadhesive Carbopol-starch components.

The purpose of this study was to evaluate different bioadhesive ocular formulations based on drum dried waxy maize starch (DDWM), Amioca starch and Carbopol 974P. The concentrations of Carbopol 974P in the mixtures varied between 5 and 25% (w/w). The rheological properties of the non-sterilized and gamma-irradiated physical blends of Carbopol 974P with either DDWM or Amioca were compared to those of the corresponding co-spray dried Amioca starch/Carbopol powders. Higher viscosity or consistency values were measured for sterilized co-spray dried powder mixtures containing an amount of Carbopol 974P equal or above 15% (w/w) compared to the physical blends. Sustained release minitablets (2 mm, 6 mg), consisting of sodium fluorescein as model drug and the bioadhesive powders, were manufactured at a compression force of 1.25 kN. Afterwards, the tablets were sterilized with gamma-irradiation. The amount of Carbopol in the co-spray dried powder mixtures on the one hand and gamma-irradiation on the other hand had no significant influence on the crushing strength and friability of the minitablets evaluated. However, these two factors affected the in vitro release properties of the minitablets. The slowest release was obtained with tablets containing 25% Carbopol 974P, which unfortunately possess mucosal irritating properties. By using co-spray dried Amioca with 15% (w/w) Carbopol 974P, a slower release can be achieved compared to the physical mixtures of DDWM or Amioca starch with Carbopol 974P. Moreover, this ocular formulation is very promising and is preferred, as it did not cause any mucosal irritation and released the model drug for at least 12 h, after application in the fornix.

Acrylic Resins↗
PubMed2005

Lactic acid bacteria and yeasts associated with spontaneous fermentations during the production of sour cassava starch in Brazil.

Sour cassava starch is a traditional fermented food used in the preparation of fried foods and baked goods such as traditional cheese breads in Brazil. Thirty samples of sour cassava starch were collected from two factories in the state of Minas Gerais. The samples were examined for the presence of lactic acid bacteria, yeasts, mesophilic microorganisms, Bacillus cereus and faecal coliforms. Lactic acid bacteria and yeasts isolates were identified by biochemical tests, and the identities were confirmed by molecular methods. Lactobacillus plantarum and Lactobacillus fermentum were the prevalent lactic acid bacteria in product from both factories, at numbers between 6.0 and 9.0 log cfu g(-)(1). Lactobacillus perolans and Lactobacillus brevis were minor fractions of the population. Galactomyces geothricum and Issatchenkia sp. were the prevalent yeasts at numbers of 5.0 log cfu g(-)(1). A species similar to Candida ethanolica was frequently isolated from one factory. Mesophilic bacteria and amylolytic microorganisms were recovered in high numbers at all stages of the fermentation. B. cereus was found at low numbers in product at both factories. The spontaneous fermentations associated with the production of sour cassava starch involve a few species of lactic acid bacteria at high numbers and a variety of yeasts at relatively low numbers.

Bacillus cereus↗
PubMed2004

Investigations into the use of pregelatinised starch to develop powder-filled hard capsules.

The use of pregelatinised starch in tamp filling of hard capsules with powder formulations containing a low-solubility drug (theophylline anhydrous) with very poor powder flow and stickiness to metal surfaces was investigated. Twenty-one mixtures containing the drug, pregelatinised starch, lactose monohydrate and magnesium stearate were produced, with their quantitative composition based on a central composite design. These mixtures were filled into hard capsules using an instrumented tamp-filling machine. Seven different compression settings ranging from "no" to "firm" compression were employed, and the tamping force was recorded on stations 3 and 4. It was found that the use of pregelatinised starch as an excipient in the manufacture of powder-filled hard capsules could be beneficial in terms of reducing the coefficient of fill weight variability. To improve drug dissolution of poorly soluble drugs, larger amounts of this excipient were required, and the maximum capsule fill weight that could be achieved was slightly reduced at the same time.

Capsules↗
PubMed2006

Starch thickening of human milk is ineffective in reducing the gastroesophageal reflux in preterm infants: a crossover study using intraluminal impedance.

We evaluated the efficacy of the thickening of human milk by precooked starch in reducing gastroesophageal reflux in preterm infants. Five preterm infants with frequent regurgitations (median gestational age, 28 weeks; range, 27 to 32 weeks; median birth weight, 990 g; range, 570 to 1900 g) were fed alternately during 24 hours with four meals of fortified maternal milk (milk A) and four meals of fortified maternal milk thickened by 1.5 g of precooked starch per 100 mL of milk (milk B). The acidic and buffered refluxes were detected by simultaneous pH monitoring and multiple intraluminal impedance. Eight feeding periods for each baby were recorded. The number of the acidic (34 after milk A vs 36 after milk B) and buffered (112 after milk A vs 134 after milk B) episodes of gastroesophageal reflux did not differ. Thickening human milk by precooked starch is ineffective in reducing gastroesophageal reflux in premature infants.

Cross-Over Studies↗
PubMed2005

Increase of photosynthesis and starch in potato under elevated CO2 is dependent on leaf age.

Potato plants (Solanum tuberosum cv. Bintje) were grown in open top chambers under ambient (400 microL L(-1)) and elevated CO2 (720 microL L(-1)). After 50 days one half of each group was transferred to the other CO2 concentration and the effects were studied in relation to leaf age (old, middle-aged and young leaves) in each of the four groups. Under long-term exposure to elevated CO2, photosynthesis increased between 10% and 40% compared to ambient CO2. A subsequent shift of the same plants to ambient CO2 caused a 20-40% decline in photosynthetic rate, which was most pronounced in young leaves. After shifting from long-term ambient to elevated CO2, photosynthesis also increased most strongly in young leaves (90%); these experiments show that photosynthesis was downregulated in the upper young fully expanded leaves of potato growing long-term under elevated CO2. Soluble sugar content in all leaf classes under long-term exposure was stable irrespective of the CO2 treatment, however under elevated CO2 young leaves showed a strongly increased starch accumulation (up to 400%). In all leaf classes starch levels dropped in response to the shift from 720 to 400 microL L(-1) approaching ambient CO2 levels. After the shift to 720 microL L(-1), sucrose and starch levels increased, principally in young Leaves. There is clear evidence that leaves of different age vary in their responses to changes in atmospheric CO2 concentration.

Carbon Dioxide↗
PubMed2004

The catecholamine potentiates starch mobilization in transgenic potato tubers.

In human and animal cells, the catecholamines are involved in glycogen mobilization. Since the compounds are found in a potato, their function in starch mobilization was hypothesized. In order to verify this hypothesis, the transgenic potato plants Solanum tuberosum L. cv. Desiree overexpressing tyrosine decarboxylase (TD EC 4.1.1.25) cDNA from parsley has been generated. The cDNA expression was judged by the northern blot analysis and the enzyme activity measurements. Four independent transgenic lines with the highest TD mRNA expression were selected and analyzed. The expected substantial decrease in tyrosine content was followed by significant increase in tyramine and dramatic enhancement of norepinephrine synthesis was detected. The level of L-3,4-dihydroxyphenylalanin (L-Dopa) was only slightly increased and dopamine significantly decreased in most cases in these plants. The increase in norepinephrine was accompanied by changes in carbohydrate metabolism. The significant increase in glucose and sucrose and the decrease in starch content were characteristic features of TD overexpressed transgenic potato tubers. The features mentioned above indicate that catecholamines potentiate starch mobilization in potato plants in common with animal cells. The decrease in tyrosine content in transgenic plants is also compensated by significant increase in chlorogenic acid synthesis thus potentially increasing the antioxidant capacity of transgenic tubers. The glycoalkaloids content is changed in the transformants. This may originate from glucose accumulation and glycolysis activation. The obtained transgenic potato provides material for further detailed studies of the physiological function of catecholamines in plants.

Animals↗
PubMed1999

Effects of dietary consistency and water content on parotid amylase secretion and gastric starch digestion in rats.

The aim was to estimate the significance of oral sensation and mastication in inducing amylase secretion from the parotid gland and subsequent starch digestion in the stomach. Rats were fed three diets of similar chemical composition but different physical presentations. Two were solid, either pellets or powder, and one was liquid. Oral sensory activity would be greatest with the pellets and least with the liquid. Only the pellets would require significant mastication. Three criteria were used to estimate amylase secretion, amylase activity in the stomach, the depletion of glandular amylase activity and plasma amylase concentrations. Gastric starch digestion was estimated by measuring the concentration of reducing-sugars in the stomach contents. Parotid amylase secretion and gastric starch digestion were similar whether rats were fed pelleted or powdered solid food but much lower in rats fed a liquid diet. These findings support the view that it is the contact of dry food with the oral mucosa rather than the jaw movements involved in mastication that stimulates parotid amylase secretion.

Amylases↗
PubMed2000

Relationship between branching density and crystalline structure of A- and B-type maize mutant starches.

Amylopectin from two double maize mutant starches of A-crystalline (wxdu) and B-crystalline type (aewx) was subjected successively to hydrolysis involving alpha and beta amylases, which isolated clusters and all branching zones of clusters (BZC). Enzymatic analysis together with ionic and size-exclusion chromatography revealed the structural features of the clusters and BZC and their role in starch crystallization. A-type clusters were larger (dp(n) > 80) and contained more (but shorter) chains than B-type clusters. The BZC of A-type starch was also larger, but with a shorter distance between the branching points than in B-type BZC. A-type clusters had a densely packed structure and B-type a poorly branched structure. Models for the structure of A- and B-type clusters are presented, and a hypothesis for the influence of cluster geometry on crystallization is proposed.

Amylopectin↗
PubMed2002

Structural features of non-granular spherulitic maize starch.

Complementary analyses of the internal structure of spherulites crystallized from high-amylose maize starch were obtained using light, electron and atomic force microscopy. Radially oriented crystalline lamellae were observed in transmission and scanning electron microscopy, as well as AFM. Internal structures consistent with the central hilum region of starch granules were observed. Spherulites were composed largely of linear or lightly branched starch polymers. Degradation of amylopectin at gelatinization temperatures of 180 degrees C was evident, but iodine binding suggested a high molecular weight (>100 DP) for the spherulitic polymers.

Calorimetry, Differential Scanning↗
PubMed2003

Chemical synthesis of methyl 6'-alpha-maltosyl-alpha-maltotrioside and its use for investigation of the action of starch synthase II.

The branched pentasaccharide methyl 6'-alpha-maltosyl-alpha-maltotrioside was chemically synthesised and investigated as a primer for particulate starch synthase II (SSII) using starch granules prepared from the low-amylose pea mutant lam as the enzyme source. For chemical synthesis, the trichloroacetimidate activation method was used to synthesise methyl O-(2,3,4,6-tetra-O-benzyl-alpha-D-glucopyranosyl)-(1-->4)-O-(2,3,6-tri-O-benzyl-alpha-D-glucopyranosyl)-(1-->6)-O-[(2,3,4,6-tetra-O-benzyl-alpha-D-glucopyranosyl-(1-->4)]-O-(2,3-di-O-benzyl-alpha-D-glucopyranosyl)-(1-->4)-2,3,6-tri-O-benzyl-alpha-D-glucopyranoside, which was then debenzylated to provide the desired branched pentasaccharide methyl 6'-alpha-maltosyl-alpha-maltotrioside as documented by 1H and 13C NMR spectroscopy. Using a large excess of the maltoside, the pentasaccharide was tested as a substrate for starch synthase II (SSII). Both of the non-reducing ends of methyl 6'-alpha-maltosyl-alpha-maltotrioside were extended equally resulting in two hexasaccharide products in nearly equal amounts. Thus, SSII catalyses an equimolar and non-processive elongation reaction of this substrate. Accordingly, the presence of the alpha-1,6 linkages does not dictate a specific structure of the pentasaccharide in which only one of the two non-reducing ends are available for extension.

Catalysis↗
PubMed2003

Atomic force microscopy of pea starch granules: granule architecture of wild-type parent, r and rb single mutants, and the rrb double mutant.

AFM studies have been made of the internal structure of pea starch granules. The data obtained provides support for the blocklet model of starch granule structure (Carbohydr. Polym. 32 (1997) 177-191). The granules consist of hard blocklets dispersed in a softer matrix material. High-resolution images have yielded new insights into the detailed structure of growth rings within the granules. The blocklet structure is continuous throughout the granule and the growth rings originate from localised defects in blocklet production distributed around the surface of spheroidal shells within the granules. A mutation at the rb locus did not lead to significant changes in granule architecture. However, a mutation at the r locus led to loss of growth rings and changed blocklet structure. For this mutant the blocklets were distributed within a harder matrix material. This novel composite arrangement was used to explain why the granules had internal fissures and also changes in gelatinisation behaviour. It is suggested that the matrix material is the amylose component of the granule and that both amylose and amylopectin are present within the r mutant starch granules in a partially-crystalline form. Intermediate changes in granule architecture have been observed for the double mutant rrb.

Microscopy, Atomic Force↗
PubMed2000

Distribution of methyl substituents in amylose and amylopectin from methylated potato starches.

Granular potato starches were methylated in aqueous suspension with dimethyl sulfate to molar substitution (MS) values up to 0.29. Fractions containing mainly amylose or amylopectin were obtained after aqueous leaching of the derivatised starch granules. Amylopectin in these fractions was precipitated with Concanavalin A to separate it from amylose. Amylose remained in solution and was enzymatically converted into D-glucose for quantification, thereby taking into account the decreased digestibility due to the presence of methyl substituents. It was found that the MS of amylose was 1.6-1.9 times higher than that of amylopectin in methylated starch granules. The distributions of methyl substituents in trimers and tetramers, prepared from amylose- or amylopectin-enriched fractions, were determined by FAB mass spectrometry and compared with the outcome of a statistically random distribution. It turned out that substituents in amylopectin were distributed heterogeneously, whereas substitution of amylose was almost random. The results are rationalised on the basis of an organised framework that is built up from amylopectin side chains. The crystalline lamellae are less accessible for substitution than amorphous branching points and amylose.

Amylopectin↗