163 resultados para STARCH


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The physicochemical composition of pure royal jelly as well as of some adulterated samples was analyzed by determining moisture, ash, lipids, nitrogen/proteins, carbohydrates, starch and 10- HDA (10-hydroxy-2-decenoic acid). The solubility in alkaline medium was used to detect the main frauds for adulterating royal jelly which comprise addition of yogurt, water, egg white, sweet condensed milk mixed with propolis, unripe banana and corn starch slurry.

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A new titrimetric method for the determination of phosphite in fertilizer samples, based on reaction of H3PO3 with standard iodine solution in neutral media, is proposed. Diluted samples containing ca. 0.4% m/v P2O5 are heated and titrated with 0.05 mol L-1 iodine standard until the solution becomes faint yellow. Back titration is also feasible: a slight excess of titrant is added followed by starch indicator and titration is completed taking as the end point the change in color from blue to colorless. The influence of chemical composition and pH of buffers, temperature and foreign species on waiting time and end-point detection were investigated. For the Na2HPO4/NaH2PO4 buffer (pH 6.8) at 70 °C, the titration time was 10 min, corresponding to about 127 mg iodine, 200 mg KI and 174 mg Na2HPO4 and 176 mg NaH2PO4 consumed per determination. Accuracy was checked for phosphite determination in seven fertilizer samples. Results obtained by the proposed procedure were in agreement with those obtained by spectrophotometry at 95% confidence level. The R.S.D. (n=10) for direct and back titration was 0.4% and 1.3% respectively.

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Least-squares support vector machines (LS-SVM) were used as an alternative multivariate calibration method for the simultaneous quantification of some common adulterants found in powdered milk samples, using near-infrared spectroscopy. Excellent models were built using LS-SVM for determining R², RMSECV and RMSEP values. LS-SVMs show superior performance for quantifying starch, whey and sucrose in powdered milk samples in relation to PLSR. This study shows that it is possible to determine precisely the amount of one and two common adulterants simultaneously in powdered milk samples using LS-SVM and NIR spectra.

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Polysaccharide-based drilling fluids have been often applied in horizontal wells of petroleum reservoirs in Campos, Rio de Janeiro. The present study aimed to understand the mechanism of adsorption and desorption of the drill-in fluid, xanthan, modified starch and lubricant on SiO2 by means of ellipsometry. The effect of pH and brine on the mean thickness (D) of adsorbed layer was systematically investigated. The adsorption was mainly favored under alkaline conditions. A model has been proposed to explain this effect. The adsorption isotherms determined separately for xanthan and starch on SiO2 surfaces could be fitted with the Langmuir model, which yielded similar adsorption constant values.

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This work deals with the biodegradation of blends of poly(beta-hydroxybutyrate)/starch and poly(beta-hydroxybutyrate-co-hydroxyvalerate)/starch. The blends were obtained by evaporation of the solvent in the mixture of the polymers in chloroform. Tests were carried out in presence of micro-organisms which acted as biodegradation agents. The blends were consumed as carbon substrate and the production of CO2 was evaluated in the process. In addition, the polyesters' mechanical properties were reduced by the incorporation of starch in its structure. (¹H) NMR and infrared spectroscopy detected some characteristic polyester degradation groups in the polyesters' chemical structure, thus confirming the alteration suffered by it.

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The study evaluated the efficiency of chemical (phosphorylation) and physical (extrusion) modifications of the starch of broken rice. Results demonstrated a reduction in the moisture content of extruded and phosphorylated broken rice and an increase in the ash content of phosphorylated broken rice. Both phosphorylation and extrusion increased cold water binding capacity, swelling power, and solubility. Extruded and phosphorylated pastes were stable under refrigeration, but only extruded paste was stable when submitted to freezing. Phosphorylated paste had the lowest viscosity and the highest stability during heating, while the extruded one gelatinized without heating, but had higher losses during heating.

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The castor bean cake is rich in starch (48 ± 0.53%) and bears a problem linked to the occurrence of a toxic protein (ricin). The chemical hydrolysis (ratio solid:liquid = 1:6; H2SO4= 0.1 mol L-1; 120 °C; 40 min) generated a medium with 27 g L-1 of reducing sugars (hydrolysis efficiency= 32%). The hydrolyzed product was fermented and produced 11 g L-1 of ethanol (volumetric productivity=1.38 g L-1 h-1 and ethanol yield on substrate consumed=0.45 g g-1). In vivo experiments (DL50) revealed a reduction of roughly 240 times in the CBC toxicity (2.11 µg g-1).

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Biospecific affinity chromatography was used to purify three cyclodextrin glycosyl transferases (CGTases) obtained from microorganisms isolated of soil. The cyclodextrins (CDs) production by CGTases was evaluated using starches from different sources. CDs were measured through the Complexation Theory and by HPLC. CGTase from Bacillus firmus strain 7B showed the best production (30 mmol/L of β-CD and 4.3 mmol/L of γ-CD), and its cultivation conditions were optimized. The maximum enzymatic activity was achieved using lung peptone, soluble starch and agitation speed of 160 rpm. Studied CGTases were shown quite interesting for the industrial production of CDs.

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The aim of this work was to study the enzymatic modification on rice flour using lipase pancreatic and amyloglucosidase to obtain resistant starch. For this, Response Surface Methodology (RSM) was used to determine the best operating conditions for each enzyme. For lypase pancreatic, the highest value for resistant starch (45%) was achieved within 2 h reaction at pH 7 using an enzyme/substrate ratio of 4% (w/w) and Dp= 100/200 tyler. For amyloglucosidase, optima conditions corresponded to an enzyme/substrate ratio of 0,006 mL/g and Dp= 100/200 tyler at 45 ºC, yielding 57% of resistant starch in 2 h reaction. These results show the potential of using both enzymes to modified rice flour, increasing the resistant starch in about 5.7 folds in relation to the flour without treatment (resistant starch=10.6%).

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Poly (3-hydroxybutyrate) (P(3HB)) is a biopolymer, completely biodegradable, which has similar properties to fuel-based polymers. However to make it economically competitive it is necessary the study of cheap sources of substrate. The influence of hydrolyzed rice starch supplemented with soybean oil at different temperatures (30, 35 and 40 °C) was studied in the production of P(3HB) by C. necator. The percentage of P(3HB) produced in the cultures at 30, 35 °C was 30, 39% and 35, 43% without and with supplementation of oil, respectively. The culture at 40 °C showed no production phase due to a possible oxygen limitation. These results demonstrate that hydrolyzed rice starch supplemented with soybean oil increases the yield of P(3HB) and temperature of 35 ºC is the most favorable for biopolymer production.

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Chemical modification of cassava starch was conducted through an acylation reaction by using pyridine and propionic anhydride to replace the functional groups of starch. Polyurethane elastomers were prepared using suspensions of the mixture obtained from castor oil and yucca starch that was modified by a propionic anhydride reaction. The suspensions were characterized by means of tests based on The Fourier Transform Infrared Spectroscopy and the Hydroxyl Index. The castor oil-AMP suspensions were used for the PU synthesis. The PUs were characterized by their physical-mechanical properties like tension- deformation and Shore A. hardness, thermal gravimetric analysis and swelling test. The density cross-linking of from swelling tests was determined by applying the Flory-Rehner equation.

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Ethanol is the most suitable substitute for oil-based fuels. The performance of the fermentation is affected by several factors, therefore the aim of this work was to evaluate the efficiency of the fermentation of a hydrolyzed must of sweet potato using three strains of the Saccharomyces cerevisiae. It was also evaluated the effect of three forms of the processes conduction in the fermentation yield, efficiency and viability of yeast at the end process. Among the parameters evaluated, only the cell viability showed significant difference. The strain PE-2 would be the most suitable for the fermentation of the hydrolysed sweet potato.

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In this article, films were produced with six types of cassava's starch mixed with gelatin and plasticized with sorbitol. These films were used in covering of grapes 'Benitaka' (Vitis vinifera L.) as biodegradable packaging. The acetylated starch film showed the best results in solubility, thickness and homogeneity, besides the less water loss the fruit, resulting in better coverage, increasing the shelf life fruits in 12 days. These results demonstrate the great potential of using films in food conservation, adding value to agricultural activity and helping to reduce non-biodegradable plastics in the environment.

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Microcapsules containing lactoferrin were produced by spray drying using dextrin:octenylsuccinate starch, as wall materials. Porosity characteristics of spray-dried microcapsules were investigated by mercury intrusion porosimetry and nitrogen adsorption. The outer and inner structures of microcapsules were studied by Scanning Electron Microscopy and sizes were determined by Laser Diffraction. Results indicate that all microcapsules presents adsorption isotherm of type II and that micropores on the microcapsules surface will be very few or none. Our results show that microstructure, surface area and size of microcapsules are affected by dextrin: octenylsuccinate starch proportion. Pore characteristics for various microcapsules are found to be different.

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Most compounds reinforcements have been used to improve thermals, mechanical and barrier properties of biopolymers films, whose performance is usually poor when compared to those of synthetic polymers. Biodegradables films have been developed by adding mango and acerola pulps in different concentrations (0-17,1% w/w) as antioxidants active compounds to cassava starch based biodegradable films. The effect of pulps was studied in terms of tensile properties, water vapor permeability, DSC, among other analysis of the films. The study demonstrated that the properties of cassava starch biodegradable films can be significantly altered through of incorporation mango and acerola pulps.