Anhydrous Citric Acid Research Articles

Development and In Vivo Floating Behavior of Verapamil HCl Intragastric Floating Tablets

A novel gastro retentive controlled release drug delivery system of verapamil HCl was formulated in an effort to increase the gastric retention time of the dosage form and to control drug release. Hydroxypropylmethylcellulose (HPMC), carbopol, and xanthan gum were incorporated for gel-forming properties. Buoyancy was achieved by adding an effervescent mixture of sodium bicarbonate and anhydrous citric acid. In vitro drug release studies were performed, and drug release kinetics was evaluated using the linear regression method. The optimized intragastric floating tablet composed of 3:2 of HPMC K4M to xanthan gum exhibited 95.39% drug release in 24 h in vitro, while the buoyancy lag time was 36.2 s, and the intragastric floating tablet remained buoyant for >24 h. Zero-order and non-Fickian release transport was confirmed as the drug release mechanism from the optimized formulation (F7). X-ray studies showed that total buoyancy time was able to delay the gastric emptying of verapamil HCl intragastric floating tablet in mongrel dogs for more than 4 h. Optimized intragastric floating tablet showed no significant change in physical appearance, drug content, total buoyancy time, or in vitro dissolution pattern after storage at 40 degrees C/75% relative humidity for 3 months.

Fast dissolving tablets of fexofenadine HCl by effervescent method

In the present work, fast dissolving tablets of fexofenadine HCl were prepared by effervescent method with a view to enhance patient compliance. Three super-disintegrants viz., crospovidone, croscarmellose sodium and sodium starch glycolate along with sodium bicarbonate and anhydrous citric acid in different ratios were used and directly compressible mannitol (Pearlitol SD 200) to enhance mouth feel. The prepared batches of tablets were evaluated for hardness, friability, drug content uniformity and in vitro dispersion time. Based on the in vitro dispersion time (approximately 20 s), three formulations were tested for in vitro drug release pattern in pH 6.8 phosphate buffer, short-term stability at 40°/75% RH for 3 mo and drug-excipient interaction (IR spectroscopy). Among the three promising formulations, the formulation ECP3 containing 8% w/w of crospovidone and mixture of 24% w/w sodium bicarbonate 18% w/w of anhydrous citric acid emerged as the best (t50% 4 min) based on the in vitro drug release characteristics compared to conventional commercial tablet formulation (t50% 15 min). Short-term stability studies on the formulations indicated that there are no significant changes in drug content and in vitro dispersion time (P<0.05).

Design of fast disintegrating tablets of prochlorperazine maleate by effervescence method

In the present work, fast disintegrating tablets of prochlorperazine maleate were designed with a view to enhance patient compliance by effervescent method. In this method, mixtures of sodium bicarbonate and anhydrous citric acid in different ratios along with crospovidone (2-10% w/w), croscarmellose sodium (2-10% w/w) were used as superdisintegrants. Estimation of prochlorperazine maleate in the prepared tablet formulations was carried out by extracting the drug with methanol and measuring the absorbance at 254.5 nm. The prepared formulations were further evaluated for hardness, friability, drug content uniformity and in vitro dispersion time. Based on in vitro dispersion time (approximately 13-21 s), two promising formulations (one from each super-disintegrant) were tested for in vitro drug release pattern in pH 6.8 phosphate buffer, short-term stability (at 40°/75% relative humidity for 3 mo) and drug-excipient interaction (IR spectroscopy). Among the two promising formulations, the formulation containing 10% w/w of crospovidone and mixture of 20% w/w sodium bicarbonate and 15% w/w of citric acid emerged as the overall best formulation (t50% 6 min) based on drug release characteristics in pH 6.8 phosphate buffer compared to commercial conventional tablet formulation (t50% 17.4 min). Short-term stability studies on the promising formulations indicated that there are no significant changes in drug content and in vitro dispersion time (p<0.05).

Citric acid as a solid-state plasticizer for Eudragit RS PO

The use of solid-state plasticizers for the hot-melt extrusion of pharmaceutical dosage forms has been shown to be beneficial compared with liquid plasticizers. The purpose of this study was to determine the suitability of citric acid (CA) as a solid plasticizer for the preparation of Eudragit RS PO extended-release matrix systems by a melt extrusion technique. The influence of increasing levels of CA monohydrate (CA MH) or anhydrous CA in the powder blend on the extrusion process parameters (screw speed and motor load) was determined as a function of temperature. The solubility of CA MH in extruded tablets was studied by means of modulated differential scanning calorimetry (MDSC) and powder X-ray diffraction (PXRD). Films were cast from organic solutions to demonstrate the plasticizing effect of CA MH as a change in physico-mechanical properties (tensile strength, elastic modulus and elongation). The CA release from extruded tablets was studied over 12 h. The monohydrate form was found to distinctly facilitate the extrusion of Eudragit RS PO, whereas the addition of anhydrous CA to the polymer powder was less effective. This divergent behaviour in plasticization of Eudragit RS PO was attributed to the higher solubility of the monohydrate in the acrylic polymer. The plasticizing effect of the CA MH reached a plateau at 25% during hot-melt extrusion, which coincided with the solubility limit of the organic acid in the polymer as shown by MDSC and PXRD results. The CA MH increased the flexibility of Eudragit RS PO films, as demonstrated by a decrease in tensile strength and elastic modulus and an increase in elongation as a function of CA MH concentration. The dissolution of CA from the matrix tablets followed an extended-release profile, with CA MH exhibiting a faster dissolution rate than the anhydrous form. In conclusion, CA MH was found to be an effective plasticizer for Eudragit RS PO that facilitates the production of controlled-release matrix systems by hot-melt extrusion.

Characterisation of blends of paracetamol and citric acid

The purpose of this study was to characterise physically stable amorphous blends that were sticky (low glass transition temperature) in ambient conditions. The effects of composition, melting time and melting temperature were evaluated with respect to physical and chemical property. Citric acid anhydrate and paracetamol were melt-quenched as binary mixtures and as pure materials. Bulk samples were characterised by differential scanning calorimetry, X-ray powder diffractometry, and Raman and Fourier transform infrared spectroscopy. The composition and the sample exposure to moisture affected significantly the physical stability of samples. The extreme melting conditions, coupled with long exposure to heat and a high melting temperature, lowered the overall crystallisation rate. Paracetamol had a stronger tendency to crystallise from the blends than did citric acid. The 50:50% (w/w) blend was physically stable for at least 27 weeks in dry conditions and was partly crystalline after 4 weeks of storage at a relative humidity of 43%. The result of the physical stability of blends is discussed in terms of hydrogen bonding interaction between paracetamol and citric acid and in relation to degradation products formed in a mixing state.

Characterization of juice in fruits of different Chaenomeles species

The juice in fruits of 21 genotypes of Japanese quince ( Chaenomeles japonica), 1 genotype of Chinese quince ( C. cathayensis), 1 genotype of flowering quince ( C. speciosa) and 1 genotype of a hybrid taxon ( C. × superba), representing plant breeding material, was extracted and characterized. The content of juice in the fruits varied between 41% and 52%, on fresh weight basis. The juice was very acidic (pH 2.6 and a titratable acidity of 3.5% calculated as anhydrous citric acid, on average) and transparent (52 NTU, on average), with low density and viscosity. The content of soluble solids was also low (7.1°Brix, on average). Proteins constituted 26 mg/100 ml juice on average, but no soluble polysaccharides were present. A high content of vitamin C (59 mg/100 ml juice, on average) and phenols (284 mg/100 ml juice, on average), beside the high acidity of the juice, suggests that chaenomeles juice may be an interesting raw material as ingredient for the food industry and a source of valuable substances. A principal components analysis separated the Japanese quince genotypes from the other genotypes studied, thus indicating a clear difference in the characteristics and chemical composition of the juice.

Effect of Sodium Citrate on Structure-Function Relationships of Cheddar Cheese

The objective of this study was to determine the effect of sodium citrate on the structure and functionality of Cheddar cheese. The hypothesis was that citrate (sodium citrate) injection would affect cheese properties mainly through its effect on bound calcium (calculated as the difference between total calcium and the water-soluble calcium content of a cheese extract). A 9-kg block of Cheddar cheese was made, vacuum-packaged, and then stored for 2 wk at 4°C. After storage, the cheese was cut into 0.5- to 0.6-kg blocks that were vacuum-packaged and stored for 1 wk at 4°C prior to injection. Cheese blocks were then high-pressure injected with a buffer solution (pH 5.27) containing 40% (wt/wt) citric acid trisodium dihydrate and 6.25% (wt/wt) anhydrous citric acid, from zero (control) to five times (successive injections performed 24h apart). Increased citric acid content of cheese from 0.22 (uninjected) to 1.39% (after five injections) caused phosphate solubilization. Thus, the calculated bound phosphate content of cheese decreased from 0.54 to 0.45mmol/g of protein. However, unexpectedly, the soluble calcium content decreased from 0.34 (control) to 0.28mmol/g of protein (after five injections), whereas the bound calcium content remained unchanged (0.42mmol/g of protein). The decrease in soluble calcium probably resulted from the formation and concentration of crystals in the cheese surface, which was not included in samples for analysis, and from the expulsion of serum from within the cheese. Higher concentration of solutes in the water phase of cheese would increase the volume of serum, but the cheese had limited holding capacity and serum was expelled. Citrate injection increased the sodium content of cheese from 0.63 to 0.93%, but it had no effect on cheese pH (5.2). After five injections, the protein matrix expanded, occupying an increased area of cheese matrix (83 vs. 78%). Even though citrate injection had no effect on bound calcium, and thus the rate and extent of cheese flow were unaffected, increased phosphate solubilization, and possibly decreased ionic calcium content, resulted in expansion of the protein matrix and increased cheese hardness.

Stimulatory effect of alcohols (methanol and ethanol) on citric acid productivity by a 2-deoxy D-glucose resistant culture of aspergillus niger GCB-47.

The present study describes citric acid fermentation by Aspergillus niger GCB-47 in a 15-1 stainless steel stirred fermentor. Among the alcohols tested as stimulating agents, 1.0% (v/v) methanol was found to give maximum amount of anhydrous citric acid (90.02 +/- 2.2 g/l), 24 h after inoculation. This yield of citric acid was 1.96 fold higher than the control. Methanol has a direct effect on mycelial morphology and it promotes pellet formation. It also increases the cell membrane permeability to provoke more citric acid excretion from the mycelial cells. The sugar consumed and % citric acid was 108 +/- 3.8 g/l and 80.39 +/- 4.5%, respectively. The desirable mycelial morphology was in the form of small round pellets having dry cell mass 14.5 +/- 0.8 g/l. Addition of ethanol, however, did not found to enhance citric acid production, significantly. The maximum value of Yp/x (i.e., 5.825 +/- 0.25 g/g) was observed when methanol was used as a stimulating agent. The best results of anhydrous citric acid were observed, 6 days after inoculation when the initial pH of fermentation medium was kept at 6.0.

Citric acid fermentation by mutant strain of Aspergillus niger GCMC- 7using molasses based medium

Citric acid fermentation of cane-molasses by submerged fermentation in 15 L stirred fermentor (working volume 9 L) was carried out. A hyper mutant strain of Aspergillus niger GCMC-7 was used in the present study which was obtained from the culture collection of our own labs. Ferrocyanide treated molasses [K 4 Fe(CN) 6 200 ppm] medium containing sugar 150 g/l was employed as the basal fermentation medium. Different cultural conditions such as incubation temperature (30oC), initial pH (6.0), air supply (1.0 l -1 l -1 min), agitation intensity (200 rpm) and time profile (144 h after inoculation) were optimised for enhanced citric acid production. Maximum amount of anhydrous citric acid obtained during the course of study was 106.65 g/l, with a sugar consumption of 107 g/l. Final pH, ferrocyanide concentration and dry cell mass were 2.1, 60 ppm and 16.5 g/l, respectively.

A new dinuclear vanadium(V)-citrate complex from aqueous solutions. Synthetic, structural, spectroscopic, and pH-dependent studies in relevance to aqueous vanadium(V)-citrate speciation.

Vanadium interactions with low molecular mass binders in biological fluids entail the existence of vanadium species with variable chemical and biological properties. In the course of efforts to elucidate the chemistry related to such interactions, we have explored the oxidative chemistry of vanadium(III) with the physiologically relevant tricarboxylic citric acid. Aqueous reactions involving VCl(3) and anhydrous citric acid, at pH approximately 7, resulted in blue solutions. Investigation into the nature of the species arising in those solutions revealed, through UV/visible and EPR spectroscopies, oxidation of vanadium(III) to vanadium(IV). Further addition of H(2)O(2) resulted in the oxidation of vanadium(IV) to vanadium(V), and the isolation of a new vanadium(V)-citrate complex in the form of its potassium salt. Analogous reactions with K(4)[V(2)O(2)(C(6)H(4)O(7))(2)].6H(2)O and H(2)O(2) or V(2)O(5) and citrate at pH approximately 5.5 afforded the same material. Elemental analysis pointed to the molecular formulation K(4)[V(2)O(4)(C(6)H(5)O(7))(2)].5.6H(2)O (1). Complex 1 was further characterized by FT-IR and X-ray crystallography. 1 crystallizes in the triclinic space group P(-)1, with a = 11.093(4) A, b = 9.186(3) A, c = 15.503(5) A, alpha = 78.60(1) degrees, beta = 86.16(1) degrees, gamma = 69.87(1) degrees, V = 1454.0(8) A(3), and Z = 2. The X-ray structure of 1 reveals the presence of a dinuclear vanadium(V)-citrate complex containing a V(V)(2)O(2) core. The citrate ligands are triply deprotonated, and as such they bind to vanadium(V) ions, thus generating a distorted trigonal bipyramidal geometry. Binding occurs through the central alkoxide and carboxylate groups, with the remaining two terminal carboxylates being uncoordinated. One of those carboxylates is protonated and contributes to hydrogen bond formation with the deprotonated terminal carboxylate of an adjacent molecule. Therefore, an extended network of hydrogen-bonded V(V)(2)O(2)-core-containing dimers is created in the lattice of 1. pH-dependent transformations of 1 in aqueous media suggest its involvement in a web of vanadium(V)-citrate dinuclear species, consistent with past solution speciation studies investigating biologically relevant forms of vanadium.

Low temperature synthesis of pure SrSnO 3 and the (Ba xSr 1− x)SnO 3 solid solution by the polymerized complex method

Pure SrSnO 3 and (Ba 1− x Sr x )SnO 3 with compositions ( x=0, 0.25, 0.5, 0.75 and 1) were directly prepared by the polymerized complex (PC) technique based on a modified Pechini-type reaction route at the relatively low temperature of 600°C. Anhydrous citric acid (CA) was added to SnCl 4. xH 2O dissolved in ethylene glycol (EG). After complete dissolution, BaCO 3 and SrCO 3 powders were added according to the desired mole ratio of the solid solution, and the mixture was stirred at 80°C for several hours until the solution became transparent. This solution, with a molar ratio (Ba+Sr)/Sn/CA/EG=1/1/10/40, was heated at 130°C to produce a yellowish transparent resin without any precipitation. The pyrolysis of the resin at 350°C yielded a powder precursor for (Ba,Sr)SnO 3. Pure SrSnO 3 is found with a pseudo cubic structure, which has some deviation from the perfect cubic lattice. X-ray diffraction (XRD) indicated the formation of pseudo-cubic (Ba,Sr)SnO 3 when the barium, strontium–tin precursor was heat treated in air at 600°C or above for 2 h. The solid solution of (Ba,Sr)SnO 3 exhibited a transition from the ideal cubic structure to a pseudo cubic structure.

A Process to Produce Effervescent Tablets: Fluidized Bed Dryer Melt Granulation

The purpose of the present study was to apply melt granulation in a fluidized bed dryer (fluidized bed dryer melt granulation) to manufacture one-step effervescent granules composed of anhydrous citric acid and sodium bicarbonate to make tablets. This study permitted us to establish that such process parameters as concentrations of polyethylene glycol (PEG) 6000, residence times in the fluidized bed dryer, fineness of PEG6000, fineness of initial mixture effervescent systems, and efficiency of two lubricants markedly affect some granule and tablet characteristics. It is a dry process that is simple, rapid, effective, economical, reproducible, and particularly adapted to produce effervescent granules that are easily compressed into effervescent tablets.

Preparation of pure perovskite-type BaSnO 3 powders by the polymerized complex method at reduced temperature

Cubic perovskite-type pure barium stannate, BaSnO 3, powders were prepared using the polymerized complex technique at the relatively low temperature of 600°C. SnCl 4· xH 2O was first dissolved in ethylene glycol (EG) and anhydrous citric acid (CA) was then added. After complete dissolution, BaCO 3 powder was added and the mixture was stirred at 80°C for several hours until the solution became transparent, demonstrating the presence of Ba 2+- and Sn 4+–citric acid complexes. This solution, with molar ratio Ba/Sn/CA/EG=1:1:10:40, was heated at 130°C to produce a yellowish transparent resin without any precipitation via polymerization with citric acid and ethylene glycol including the complexes. Pyrolysis of the resin at 350°C yielded a powder precursor of BaSnO 3. X-ray diffraction and Raman analysis indicated the formation of pseudo-cubic BaSnO 3 when the barium–tin precursor was heat treated in air at ≥600°C for 2 h. The product was identified as pseudo-cubic BaSnO 3 with lattice parameter a 0=0.4118±0.0003 nm. The powder formed at 800°C consisted of faceted microcrystals 80–100 nm in size.

The modification of lactic acid based poly(ester-urethane) by copolymerization

Copolymers of L-lactic acid (LLA) with DL-mandelic acid (DLMA), 4-hydroxybenzoic acid, 4-acetoxybenzoic acid, DL-malic acid, or anhydrous citric acid were synthesized via direct copolycondensation in the presence of 1,4-butanediol, using stannous octoate as catalyst. The effect of the comonomer and the comonomer ratio on polycondensation and the glass transition temperature were investigated. The glass transition temperature of amorphous poly(L-lactic acid-co-DL-mandelic acid) increased linearly from 33° to 56°C as the mandelic acid composition was increased from 0 to 45 mol %. For urethane synthesis, prepolymers of LLA and DLMA were condensation polymerized with compositions of 100/0, 90/10, and 80/20 (mol % in feed). The preparation of poly(ester-urethane) (PEU) was carried out in a stirred glass reactor, using 1,6-hexamethylene diisocyanate and isophorone diisocyanate in melt. The glass transition temperature of poly(L-lactic acid-co-DL-mandelic acid-urethanes) showed a marked increase with increased mandelic acid composition. The molecular weights of these urethanes were lower than for PEU based on poly(L-lactic acid). Such a depression in the degree of polymerization is attributed to the steric hindrance of the bulky phenyl group as a side chain of mandelic acid. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1865–1872, 1997

Microscopic evaluation of structural changes in brittle, hydrated, gelatin capsules

Gelatin capsules are a commonly used dosage form for prescription medications. Storage conditions as well as drug formulation can directly affect capsule integrity over time. Often, capsule brittleness following storage can be related to water loss. In this report an encapsulated drug formulation containing 77% anhydrous citric acid became brittle following two years of storage at 25° C/60% RH. However, Thermogravimetric data showed that capsule brittleness did not result from changes in water content. Both normal(without drug formulation) and brittle capsules contained 12% water. Microscopy was then applied to examine capsule walls to determine if the change in physical integrity could be related to a structural change.LM of normal capsules showed both the interior and exterior walls to be smooth, without indentations. SEM examination of the interior wall of the normal capsules revealed fairly smooth walls (Fig. 1). Sections of normal capsules examined with the TEM revealed intact walls with little variation between sections or capsules (Fig. 2). Examination of capsules stored for one year revealed interior surfaces stippled with particulate identified as active ingredient(AI) and citric acid. The particulate was not fused to the interior wall and no morphological changes were observed for the Al or citric acid when compared to known active/excipient morphology. In contrast, the interior wall of capsules stored for two years showed striking morphological changes. LM presented an eroded interior wall indicating a loss or redistribution of gelatin. TEM further illustrated that the structure of the capsule had been altered; subsurface pockets were seen throughout the section of the capsule (Fig. 3). TiO2 particles, a whitener used in the capsules, were redistributed in the areas where degradation was apparent. SEM presented irregular interior surfaces with abundant particulate fused to the capsule wall (Fig. 4). The fused particulate presented structure which contrasted with the known morphology of the citric acid and Al starting materials indicating that dissolution and recrystallization had taken place. Comparable crystal structure was determined when Al and citric acid were dissolved in water and allowed to recrystallize at room temperature.

Effect of growing conditions on the corrosivity and ascorbic acid retention in canned tomato juice

AbstractTomatoes (Lycopersicon esculentum) (M82‐1‐8) grown hydroponically in a greenhouse experiment at 16 combinations of nitrate/chloride nutrient solutions were processed as juice and the canned product was stored at 22°C and 36°C for 27 months to study corrosion of the packs from the point of view of detinning or delamination of the internal lacquer and comparative retention of ascorbic acid content.Detinning in plain tinplate cans was greater with juices from tomatoes grown in high nitrate, low chloride solution as a result of the high nitrate content of tomatoes. Addition of chloride decreased the nitrate uptake of the tomatoes, thereby reducing detinning in plain cans significantly. A relevant positive correlation between detinning and high nitrate, high chloride nutrient regime after 27 months storage was attributed to an increase in total acid (as anhydrous citric acid) content of the respective juices and hence increased corrosivity.Delamination, with underfilm corrosion, in lacquered cans was correlated with tomatoes grown under a higher nitrate, medium chloride regime, giving medium levels of nitrate (0.30‐0.65 mmol litre−1) and chloride (20‐25 mmol litre−1) but higher levels of acidity (24‐37 mmol litre−1 citric acid) in the juice. Tomatoes grown under a higher nitrate, low chloride regime exhibited nitrate concentrations as high as 1.0 mmol litre−1 and high corrosivity. Tomatoes grown under low nitrate and increasing levels of chloride regimes gave juices containing as low as 0.18 mmol litre−1 of nitrate but higher chloride concentrations up to 42 mmol‐litre−1; no delamination was observed in lacquered cans of these juices but some pitting corrosion and perforations occurred at the end of 27 months at 36°C.Ascorbic acid retention was mainly correlated with the type of can as well as with the initial ascorbic acid level of the raw tomatoes, itself the result of the interaction of Cl− and NO3− in the nutrient solution. During 27 months storage, the ascorbic acid retention was consistently higher in tomato juice canned in plain tinplate cans (88 % at 22°C or 70% at 36°C) than in lacquered cans (24% at 22°C or 18% at 36°C).

Phytotoxicity of petroleum spray oils to Valencia orange, Citrus sinensis (L.) Osbeck, in New South Wales

The phytotoxicity of petroleum oil sprays to Vakncia orange (Citrus sinensis (L.) Osbeck) on Poncirus trifoliata (L.) Raf. rootstocks was investigated at Kulnura and at Griffith, New South Wales. Four narrow-range petroleum oils, designated as 206, 212, 214 and 238 oils, were applied as high volume sprays in 3 consecutive years. Annual sprays were applied during the spring, summer and autumn months of November, February and April. Some treatments were sprayed once each year, others twice. The single spray per year treatments involved concentrations of 1.2 or 2% of each oil in February or 2% of the 212, 214 and 238 oils in November or in April. A total concentration of 3.2% oil per year of the 2 12,2 14 and 238 oils was applied in February (2%) and in November of the previous year (1.2%) or in April (1.2%) to the double spray treatments. The effect of the sprays on yield variables, percentage juice, �Brix (w/w sucrose), anhydrous citric acid, rind colour and oil content was studied. Rind colour was not affected by any treatment at either location. Significant (P&lt; 0.05), though inconsistent, effects on other characteristics of fruit quality were found. Increase in 50% distillation temperature and rate of application of oils tended to decrease �Brix. The oils did not significantly affect yield at Kulnura. At Griffith, 2% sprays of 238 oil significantly reduced yield by reducing the number of fruit. At both locations, trees sprayed with 2% oil in April tended to have lower yields than those sprayed in November or February at the same rate. The effect of sprays with total concentrations of 3.2% was variable. The 238 oil was the only oil considered to be potentially phytotoxic. This type of oil should not be used at concentrations &gt; 2% from March to November or in consecutive years at any time. They can be used from late spring to early autumn in consecutive years at 1.2%. Variation in the phytotoxicity of oils between locations in south-eastern Australia appears to be related to variation in night temperatures in summer and early autumn which affect flower initiation.

Absence of mutagenic activity of acidity regulators in the Ames Salmonella/microsome test

The activities of various concentrations of 4 acidity regulators (anhydrous citric acid, phosphoric acid, malic acid and lactic acid) used in food industries in Iraq was assayed using the Salmonella/microsome mutagenicity assay. None of the samples was mutagenic in the absence or in the presence of S9 to any of the tester strains of Salmonella typhimurium.

Extrusion of an Effervescent Granulation with a Twin Screw Extruder, Baker Perkins MPF 50 D. Influence on Intragranular Porosity and Liquid Saturation

Anhydrous citric acid and sodium bicarbonate were granulated with ethanol in an extruder. The influence of the following process variables on intragranular porosity and liquid saturation was investigated: powder flow rate, ethanol concentration, screw speed, die plate and screw configuration.Granule porosity was significantly influenced by screw configuration and ethanol concentration. Besides, the porosity was also correlated with response variables that affected the decomposition of sodium bicarbonate. A more intense screw configuration enhanced the formation of carbon dioxide due to a temperature rise and consequently increased porosity. On the other hand, a higher ethanol concentration reduced the porosity.There was a strong correlation between intragranular porosity and liquid saturation.

Citric acid production using immobilized conidia of Aspergillus niger TMB 2022

Conidia of Aspergillus niger TMB 2022 were immobilized in calcium alginate for the production of citric acid. A 1-mL conidia suspension containing ca. 2.32 x 10(8) conidia were entrapped into sodium alginate solution in order to prepare 3% Ca-alginate (w/v) gel bead. Immobilized conidia were inoculated into productive medium containing 14% sucrose, 0.25% (NH(4))(2)CO(3), 0.25% KH(2)PO(4), and 0.025% MgSO(4).7H(2)O with addition of 0.06 mg/L CuSO(4).5H(2)O, 0.25 mg/L ZnCl(2), 1.3 mg/L FeCl(3).6H(2)O, pH 3.8, and incubated at 35 degrees C for 13 days by surface culture to produce 61.53 g/L anhydrous citric acid. Under the same conditions with a batchwise culture, it was found that immobilized conidia could maintain a longer period for citric acid production (31 days): over 70 g/L anhydrous citric acid from runs No. 2-4, with the maximum yield for anhydrous citric acid reaching 77.02 g/L for run No. 2. In contrast, free conidia maintained a shorter acid-producing phase, ca. 17 days; the maximum yield for anhydrous citric acid was 71.07 g/L for run No. 2 but dropped quickly as the run number increased.