Showing papers on "Citric acid published in 1983"

Food preservative composition

Abstract: This invention resides in a composition for treatment of meat, poultry, fruit and vegetables to maintain the color and to preserve same. The composition comprises as essential constituents between about 10 and 40% each of the following materials: (1) ascorbic acid and/or the sodium or potassium salts thereof; (2) citric acid and/or the sodium or potassium salts thereof; (3) sodium or potassium carbonate; and (4) sulfite, bisulfite or metabisulfite of sodium or potassium. These materials represent a synergistic combination which preserves the color and freshness of these products for a surprisingly long period of time.

Citrate excretion: a window on renal metabolism.

Abstract: The rate of intracellular metabolism of citrate plays a major role in determining the amount of citrate excreted in the urine. Fractional excretion of citrate can be increased either by increasing intracellular citrate synthesis from precursors or by inhibiting mitochondrial citrate metabolism. Increased excretion secondary to increased synthesis of citrate occurs when citric acid cycle precursors such as malate or succinate are infused. Increased excretion resulting from inhibition of citrate metabolism occurs when malonate, maleate, or fluorocitrate is administered. Systemic acid-base changes cause striking changes in citrate clearance and metabolism. Recent evidence suggests that the effects of acid-base changes are mediated by alteration in the pH gradient across the inner mitochondrial membrane. Metabolic alkalosis causes cytoplasmic pH and bicarbonate to increase, resulting in a decrease in the mitochondrial pH gradient. This change inhibits the tricarboxylate carrier, slowing entry of citrate into the mitochondrial matrix compartment. The level of citrate in the cytoplasm increases, tubular and peritubular citrate uptake are reduced, and citrate clearance increases. Opposite changes occur in acidosis. Change in the mitochondrial pH gradient provides a sensitive mechanism for regulating renal substrate metabolism.

Mössbauer and EPR studies of activated aconitase: development of a localized valence state at a subsite of the [4Fe-4S] cluster on binding of citrate

Abstract: During activation of aconitase a ferrous ion is incorporated into a [3Fe-4S] cluster to yield a structure with a [4Fe-4S] core. Using 57Fe or 56Fe for activation we have studied with Mossbauer spectroscopy the beef heart enzyme in the presence of citrate. Our studies show that the environment of one iron site (Fea) of the [4Fe-4S] cluster is drastically altered in the presence of citrate. Fea is the iron acquired during activation of aconitase. In the oxidized [4Fe-4S]2+ state two species with enzyme-bound substrate are observed, whereas only one is observed in the reduced [4Fe-4S]+ state. The Mossbauer parameters of Fea reveal that the site has acquired substantial high-spin ferrous character. This is most pronounced in the 1+ state where at Fea the cluster exhibits a localized valence state. The dramatic increase of the isomer shift upon substrate binding strongly suggests that the ligand environment of Fea has become at least five-coordinate and that the cluster may function as a Lewis acid. In the absence of citrate the EPR spectra of the active [4Fe-4S]+ enzyme (g1,2,3 = 2.06, 1.93, 1.86) show no hyperfine broadening in the presence of H2 17O. However, in the presence of citrate (g1,2,3 = 2.04, 1.85, 1.78) sizable transferred hyperfine interactions are observed; under the experimental conditions the hydroxyl groups of citrate and isocitrate as well as water are labeled with 17O. We did not detect broadening by 17O-labeled carboxyl groups of citrate in H2 16O. Implications for the mechanism of aconitase are discussed.

Partial purification and regulatory properties of phosphofructokinase from Aspergillus niger.

Abstract: Phosphofructokinase (EC 2.7.1.11) from a citric acid-producing strain of Aspergillus niger was partially purified by the application of affinity chromatography on Blue Dextran--Sepharose and the use of fructose 6-phosphate and glycerol as stabilizers in the working buffer. The resulting preparation was still impure, but free of enzyme activities interfering with kinetic investigations. Kinetic studies showed that the enzyme exhibits high co-operativity with fructose 6-phosphate, but shows Michaelis--Menten kinetics with ATP, which inhibits at concentrations higher than those for maximal activity. Citrate and phosphoenolpyruvate inhibit the enzyme; citrate increases the substrate (fructose 6-phosphate) concentration for half-maximal velocity, [S]0.5, and the Hill coefficient, h. The inhibition by citrate is counteracted by NH4+, AMP and phosphate. Among univalent cations tested only NH4+ activates by decreasing the [S]0.5 for fructose 6-phosphate and h, but has no effect on Vmax. AMP and ADP activate at low and inhibit at high concentrations of fructose 6-phosphate, thereby decreasing the [S]0.5 for fructose 6-phosphate. Phosphate has no effect in the absence of citrate. The results indicate that phosphofructokinase from A. niger is a distinct species of this enzyme, with some properties similar to those of the yeast enzyme and in some other properties resembling the mammalian enzyme. The results of determinations of activity at substrate and effector concentrations resembling the conditions that occur in vivo support the hypothesis that the apparent insensitivity of the enzyme to citrate during the accumulation of citric acid in the fungus is due to counteraction of citrate inhibition by NH4+.

Control of iron induced fouling in water systems

Abstract: A method for inhibiting corrosion and controlling deposition in an iron containing aqueous medium is disclosed. The method is capable of providing for the formation of a protective passive oxide film on the metallic surfaces in contact with the aqueous medium without resulting in unacceptable iron based deposition or fouling. Surprisingly, the method does not call for the addition of an organic-phosphonic acid compound or derivative to the aqueous medium as would be normally expected due to the known iron dispersing characteristics of these type compounds. The invention comprises maintaining the pH level at 5.5 or above, assuring that a certain minimal calcium or other ion level is maintained, and adding to the system an orthophosphate compound, a water soluble acrylic acid/hydroxyalkylacrylate copolymer, and a topping agent selected from the group consisting of effective water soluble aminocarboxylic acids, lignosulfonates, citric acid, and tannic acid, and water soluble salt forms and mixtures thereof.

Time-dependent leaching of coal fly ash by chelating agents

Abstract: The rates of leaching of several transition-metal ions from coal fly ash by pH 74 solutions of the chelating agents citric acid, EDTA, Listidine and glycine have been measured as part of an investigation of the potential health effects of inhaled fly ash The results are compared to leaching of the same fly ash by 05M HCl, 010 M pH 74 Tris buffer, 05 M NH/sub 4/OH, and canine serum For the trace elements, Zn, Mn, G, Ni, and Cu, the initial leaching rates with 05 M HCl range from 350 to 850 ppm/d The rates drop by 1-2 orders of magnitude within 24 h and then level off at 1-10 ppm/d The initial rates with EDTA and citric acid are also high, 100-400 ppm/d, but they fall off even more rapidly than the HCl leaching rates The leaching of vanadium is exceptionally rapid, with initial rates of 1000-3000 ppm/d

Chemical factors affecting the intestinal absorption of zinc in vitro and in vivo.

Abstract: Everted sacs of rat duodenum and ileum were used to study the effect of anions and organic ligands on the absorption of zinc. The uptake per unit weight of tissue was greater in duodenum than ileum, and it was influenced by the Zn concentration and pH of the incubation medium. The Zn uptake from inorganic salts in simple buffered medium varied in the order zinc sulphate greater than zinc chloride greater than zinc phosphate. Zinc acetate was more effective and zinc citrate less effective than ZnCl2. Addition of aspartic acid or histidine to ZnCl2 increased the uptake but galactose or lactose decreased it. 2-Picolinic acid greatly increased the Zn uptake but 4-picolinic acid reduced it. When incubated with intestinal sacs after incorporation into a synthetic rat diet, only ZnSO4 and 2-picolinic acid increased Zn uptake compared with ZnCl2, but zinc citrate and 4-picolinic acid still tended to decrease it. Metabolic balance studies showed no significant differences in the faecal excretion, total excretion or retention of Zn between rats receiving diets containing different forms of Zn. ZnSO4, zinc citrate and particularly 2-picolinic acid increased the urinary excretion of Zn. The significance of these results is discussed in relation to the suitability of methods for investigating Zn absorption and the importance of Zn-binding ligands.

Liquid-chromatographic determination of indole-3-acetic acid and 5-hydroxyindole-3-acetic acid in human plasma.

Abstract: We describe a "high-performance" reversed-phase liquid-chromatographic method for determination of indole-3-acetic acid (I) and 5-hydroxyindole-3-acetic acid (II) in human plasma. I is eluted at 1.0 mL/min with a mixture of 1-pentanesulfonic acid (pH 3.1), methanol, and water. It is detected by fluorometry. A mixture of citric acid/sodium phosphate solution (pH 4.8) and methanol, at 1.5 mL/min, is used to elute II, which is detected with an electrochemical cell. Platelet-poor plasma samples were pretreated with HCl, perchloric acid, and trichloroacetic acid for protein precipitation. Best results were obtained with the last (protein precipitation is incomplete with HCl, while recoveries of I are concentration dependent with perchloric acid). Analytical recoveries were 58% (SD 3.1%, CV 5.3%, n = 12) and 79% (SD 3.3%, CV 5.3%, n = 9) for I and II, respectively. Concentrations of I and II in plasma ranged from 0.61 to 3.32 (mean 1.54, SD 0.59, n = 15) mumol/L and from 33.0 to 102.6 (mean 51.8, SD 20.1, n = 16) nmol/L, respectively.

Tomato Seed Protein Concentrates: Effects of Methods of Recovery Upon Yield and Compositional Characteristics

Abstract: Tomato seed protein concentrates (TSPC) were recovered from ground tomato seeds using alkaline extraction and three different protein coagulants (citric acid, citric acid/hydrochloric acid mixture or hydrochloric acid) at three coagulation temperatures (25°C 60°C or 95°C). The effect of this 3 × 3 protein recovery matrix on protein yield and composition of the freeze-dried TSPC was studied. No significant effect of protein coagulants on protein yield (TCA/heat coaguable protein) was found but it was significantly higher with samples coagulated at 25°C than when heat coagulation was applied. Coagulation procedures at room temperature resulted in lower moisture, crude fat and ash concentration than heat coagulated samples. Lowry protein content of TSPC was not significantly affected by recovery methods but crude protein content after coagulation with citric acid resulted in significantly higher values of the samples coagulated at 25°C than those at 95°C.

Preparation of colorless sunflower protein products: Effect of processing on physicochemical and nutritional properties

Abstract: A comparison was made of the different technological treatments for the preparation of colorless sunflower protein products from the viewpoint of the effect of processing conditions on the extraction yield of nitrogen and lipid, chemical, physicochemical and nutritional properties of the processed products. The technological treatments comprised soaking dehulled seeds in dilute citric acid or sodium bisulfite solution and washing the defatted meal with the respective solution. The defatting process was carried out with hexane or azeotrope (hexane/ethanol). Nitrogen and lipid recovery was slightly greater for hexane defatted products than for azeotrope defatted products. About 21.4% of the phenolic compounds of the sunflower seeds were bound to the proteins of the seeds before processing and therefore could not be eliminated by the aqueous extraction. Aqueous extraction of phenolic compounds was limited for full fat seed. The free phenolic compounds were very stable in acid medium but sensitive to oxidation in alkaline medium and had no significant effect on in vitro enzymatic proteolysis and growth inhibition of rats. Lysine and the bound phenolic compounds were the critical factors responsible for inhibition of enzymatic proteolysis and reduced growth of rats. The diet containing whole seed meal presented a low protein efficiency ratio (PER) value. Citric acid, a chelating agent, proved to be an antioxidant as effective as sodium bisulfite; the products obtained by citric acid treatment had a visually whiter color than those processed by sodium bisulfite.

Production of citric acid from whey permeate by fermentation using Aspergillus niger

Abstract: The use of lactic casein whey permeate as a substrate for citric acid production by fermentation has been investigated. Using a mutant strain of Aspergillus niger IMI 41874 in fermenter culture, a citric acid concentration of 8.3 g/l, representing a yield of 19% (w/w) based on lactose utilized, has been observed. Supplementation of the permeate with lactose (final concentration 140 g/l) increased the production to 14.8 g/l (yield 23%). The natural pH of the permeate (pH 4.5) was the most suitable initial pH for the process, and pH control during the fermentation was unnecessary. The addition of methanol (final concentration 3% v/v) to the fermentation increased the citric acid production to 25 g/l (yield 33%, based on lactose utilized). 13 references.

Microbial production of citric acid

Abstract: Characteristics of the fermentation process Sucrose is fermented to lactic acid by a culture of lactic acid bacteria. The fermentation is carried out batchwise at a temperature above 50 ~ Strict sterile conditions are not necessary. In contrast to earlier described industrial processes, in this process the pH is kept constant by the addition of lime. The yield of lactic acid is more than 90%, with an L(+)-isomer content of about 97%.

Detection and Control of Soymilk Astringency

Abstract: Soymilk was made less astringent by the addition of skimmed cow's milk (SCM), CaSO4 or citric acid. The additions of CaSO4 and citric acid were not sufficient to cause visible separation of soymilk solids, but there was some difference in mouthfeel due to the additions. Warm temperatures (65°C) of the soymilk resulted in a loss of astringency compared to sensory evaluation at room temperature or 4°C. Analyses for total polyphenols showed statistically significant decreases in apparent polyphenol content per gram of soymilk solids with the first level of addition of SCM, CaSO4, or citric acid but not with subsequent additions.

Partial Purification and Properties of an Alkaline α-Galactosidase from Mature Leaves of Cucurbita pepo

Abstract: A fourth molecular from of α-galactosidase, designated LIV, an alkaline α-galactosidase, was isolated from leaves of Cucurbita pepo and purified 165-fold. It was active over a narrow pH range with optimal hydrolysis of p-nitrophenyl-α-d-galactoside and stachyose at pH 7.5. The rate of stachyose hydrolysis was 10 times that of raffinose. Km determinations in McIlvaine buffer (200 millimolar Na2-phosphate, 100 millimolar citric acid, pH 7.5) for p-nitrophenyl-α-d-galactoside, stachyose, and raffinose were 1.40, 4.5, and 36.4 millimolar, respectively. LIV was partially inhibited by Ca2+, Mg2+, and Mn2+, more so by Ni2+, Zn2+, and Co2+, and highly so by Cu2+, Ag2+, Hg2+ and by p-chloromercuribenzoate. It was not inhibited by high concentrations of the substrate p-nitrophenyl-α-d-galactoside or by myo-inositol, but α-d-galactose was a strong inhibitor. As observed for most other forms of α-galactosidase, LIV only catalyzed the hydrolysis of glycosides possessing the α-d-galactose configuration at C1, C2, and C4, and did not hydrolyze p-nitrophenyl-α-d-fucoside (α-d-galactose substituted at C6). The enzyme was highly sensitive to buffers and chelating agents. Maximum hydrolytic activity for p-nitrophenyl-α-d-galactoside was obtained in McIlvaine buffer (pH 7.5). In 10 millimolar triethanolaminehydrochloride-NaOH (pH 7.5) or 10 millimolar Hepes-NaOH (pH 7.5), hydrolytic activity was virtually eliminated, but the addition of low concentrations of either ethylenediaminetetraacetate or citrate to these buffers restored activity almost completely. Partial restoration of activity was also observed, but at higher concentrations, with pyruvate and malate. Similar effects were found for stachyose hydrolysis, but in addition some inhibition of LIV in McIlvaine buffer, possibly due to the high phosphate concentration, was observed with this substrate. It is questionable whether the organic acid anions possess any regulatory control of LIVin vivo. It was possible that the results reflected the ability of these anions, and ethylene-diaminetetraacetate, to restore LIV activity through coordination with some toxic cation introduced as a buffer contaminant.

Method of removing copper and copper oxide from a ferrous metal surface

Abstract: A method of removing copper and copper oxide from a ferrous metal surface comprising contacting said metal and said copper oxide with an aqueous composition having a pH from about 3.0 to about 6.0 and comprising an oxidizing agent, a compound selected from the group consisting of oxalic acid, the alkali metal, and ammonium salts of oxalic acid and mixtures thereof, and an ingredient selected from the group consisting of citric acid, polyaminocarboxylic acids, the ammonium and alkali metal salts of citric acid and polyaminocarboxylic acids and mixtures thereof.

Citrate uptake by basolateral and luminal membrane vesicles from rabbit kidney cortex.

Abstract: The mechanisms of tubular transport of citrate in renal basolateral and luminal membrane vesicles were studied under various experimental conditions. Both membrane preparations take up citrate by a Na+-dependent transport system, although with different characteristics. The uptake of citrate by basolateral membrane vesicles was insensitive to changes in membrane potential, which is indicative of electroneutral transport of the anion. The Na+-dependent uptake of citrate by luminal membrane vesicles was influenced by the presence of Na+salt anions of different permeabilities in the order: chloride greater than sulfate greater than gluconate. Furthermore, addition of citrate to membrane vesicle-potential-sensitive dye suspensions resulted in optical changes of the dye, indicative of electrogenic transfer of this compound. The apparent affinity of the citrate transport system located in luminal membrane vesicles, in contrast to basolateral membrane vesicles, was sensitive to changes in medium pH and was higher than that of basolateral membrane vesicles in the pH range studied. On the basis of these results a model for the transport of citrate by rabbit kidney proximal tubule is proposed.

Use of immobilized cells of the yeast,Saccharomycopsis lipolytica, for the production of citric acid

Abstract: A strain ofSaccharomycopsis lipolytica was immobilized in polyacrylamide gel, and its ability to produce citric acid from glucose was examined. The immobilization procedure caused no loss of activity, and production rates of 50 mg/l.h (10 mg/g dry wt. original cells.h) were maintained for 45 days. The immobilized cells could be stored at 4°C for 14 days without loss of activity.

Relation between gastric secretion of acid and urinary excretion of calcium after oral supplements of calcium

Abstract: The object of this study was to determine in 12 healthy subjects the relation between gastric secretion of acid and absorption of calcium from two different preparations of calcium, as judged from increased outputs of calcium in the urine. The increase in urinary output of calcium after solid calcium carbonate was greater in the subjects with the most gastric secretion of acid. The absorption of calcium after a solution of monocalcium citrate was independent of gastric secretion of acid. In the four subjects with the least gastric secretion of acid, there was no absorption of calcium after calcium carbonate, but the absorption after monocalcium citrate was as great as that for those who secreted greater amounts of acid.

Pharmacokinetics of chlortetracycline potentiation with citric acid in the chicken

Abstract: Serum concentrations of chlortetracycline (CTC) in healthy chickens were determined for the 24-hour period after they were given CTC (with and without citric acid) as an oral (25 mg/kg) or IV (0.9 mg/kg) dose. The oral time-course drug data were fitted adequately by a 2-compartment pharmacokinetic model with absorption. The resulting absorption rate constant (Ka) for the birds orally given CTC with citric acid was nearly equal to that for the birds given CTC alone. Although the uptake of orally administered CTC was rapid, only a small fraction of the dose was absorbed. The administration of citric acid-CTC significantly increased the mean serum concentration of CTC and the fraction of the dose absorbed. The citric acid-CTC mixture also produced significantly higher elimination (Kel) and distribution (K12) rate constants for CTC.

Powdery pharmaceutical composition of myeloperoxidase

Abstract: A powdery pharmaceutical composition of myeloperoxidase comprises myeloperoxidase and an amount, enough to stabilize the myeloperoxidase, of citric acid or a salt thereof.

Importance of calcium in citric acid-induced airway constriction.

Abstract: In previous studies, a 5-min inhalational challenge with 10% citric acid aerosol (0.52 M) elicited bronchoconstriction in Basenji-Greyhound (BG) dogs with hyperreactive airways but not in mongrel dogs. This response was independent of vagal reflexes because it was not attenuated by atropine. Citric acid might elicit bronchoconstriction because of acidity, calcium chelation, or some other effect of the citrate molecule. To assess these factors, barbiturate-anesthetized BG dogs were challenged (5 min) with aerosols of 10% acetic acid or a citric acid (0.48 M)/Na3citrate (0.04 M) mixture of equivalent pH, 6% Na2-ethylenediaminetetraacetic acid (EDTA), or 6% CaNa2EDTA. Each challenge was delivered in a separate week. The acidity alone was not an adequate stimulus, since pulmonary resistance (RL) was unaltered by 10% acetic acid, although markedly increased by the citric acid-Na3citrate mixture [2.2 +/- 0.4 (SE) cmH2O X l-1 X s prechallenge, 10.0 +/- 2.2 postchallenge]. Aerosols of Na2EDTA provoked a similar increase in RL (2.1 +/- 0.4 cmH2O X l-1 X s prechallenge, 9.0 +/- 1.8 postchallenge). Neither effect was attenuated by intravenous atropine (0.2 mg/kg). CaNa2EDTA caused no changes in RL. We conclude that it is the calcium chelating action of citric acid rather than its acidity that is responsible for bronchoconstriction in BG dogs with hyperreactive airways.

Photochemical studies of the MoVI citric acid complex Mo2O5OH(H2O)(C6H5O7)2

Abstract: The bridged dimeric MoVI complexes of citric acid M2[Mo2O5OH(H2O)(C6H5O7)] · 0.5 H2O, M=K+, NH4+, have been synthesized. In the solid state they undergo an irreversible photochemical reaction to yield CO2, MoV species and acetone dicarboxylic acid. In aqueous solution the ligand decomposition proceeds further to yield acetone as the main product. The results are compared with other related studies.

A Synergistic Chelation System for Acidizing in the Presence of High Iron Concentrations

Abstract: A series of screening tests have been performed to determine the chemical types needed for chelating iron (Fe+++) at concentrations as high as 50,000 ppm in spent acid. The chemicals tested were liquid citric acid, nitrilotriacetate, and acetic acid. A blend of liquid citric acid and nitrilotriacetate was found to be practical in a 50-50 volume blend with acetic acid added in some cases as an intensifier and pH buffer. The testing was done at room temperature (80 F, 27.7/sup 0/C) and verified at 170 F (77/sup 0/C). Compatibility tests and freeze-thaw tests also were run on the blend. From the data, a practical loading schedule for use in the field has been proposed.

Process of preparing hydrogenation catalysts

Abstract: A process for the production of hydrogenation catalysts is disclosed which is characterized by the use of citric acid or malic acid as a stabilizer in a specified amount with respect to Group VI metal salts which are used in combination with Group VIII metal salts to produce an impregnating solution. The solution is impregnated with alumina or silica-alumina and calcined to form a catalyst.