Showing papers on "Citric acid published in 1995"

Organic acid exudation as an aluminum-tolerance mechanism in maize (Zea mays L.)

Abstract: In this study, the role of root organic acid synthesis and exudation in the mechanism of aluminum tolerance was examined in Al-tolerant (South American 3) and Al-sensitive (Tuxpeno and South American 5) maize genotypes. In a growth solution containing 6 μM Al3+, Tuxpeno and South American 5 were found to be two- and threefold more sensitive to Al than South American 3. Root organic acid content and organic acid exudation from the entire root system into the bulk solution were investigated via high-performance liquid chromatographic analysis while exudates collected separately from the root apex or a mature root region (using a dividedroot-chamber technique) were analyzed with a more-sensitive ion chromatography system. In both the Al-tolerant and Al-sensitive lines, Al treatment significantly increased the total root content of organic acids, which was likely the result of Al stress and not the cause of the observed differential Al tolerance. In the absence of Al, small amounts of citrate were exuded into the solution bathing the roots. Aluminum exposure triggered a stimulation of citrate release in the Al-tolerant but not in the Al-sensitive genotypes; this response was localized to the root apex of the Al-tolerant genotype. Additionally, Al exposure triggered the release of phosphate from the root apex of the Al-tolerant genotype. The same solution Al3+ activity that elicited the maximum difference in Al sensitivity between Al-tolerant and Al-sensitive genotypes also triggered maximal citrate release from the root apex of the Al-tolerant line. The significance of citrate as a potential detoxifier for aluminum is discussed. It is concluded that organic acid release by the root apex could be an important aspect of Al tolerance in maize.

Injectable non-immunogenic cartilage and bone preparation

Abstract: Ground bone or cartilage particles are demineralized by extraction with a low ionic strength buffer such as 20 mM HEPES containing a chelating agent and protease inhibitors, then extracted with an acidic solution such as 0.3 M citric acid, pH 4.0, containing protease inhibitors. The extracted material generally contains less than 2 % by weight phosphate and less than 100 mM calcium. The phosphate content can be further reduced by treatment of the matrix with acid phosphatase, which removes residual organic phosphate. The material is useful in a method of treatment of vesicoureteral reflux and other disorders where a bulking agent is effective in correcting the defect.

Flavor characteristics of lactic, malic, citric, and acetic acids at various pH levels

Abstract: The objective of this study was, through the use of free-choice profiling, to determine flavor characteristics of four acids (citric, malic, lactic, acetic) and two acid blends (lactic/acetic 1:1 and 2:1) at three different pH levels (3.5, 4.5, 6.5) and at 0.2% (w/v). Research was conducted to explores flavor differences and similarities among common food acidulants. Generalized Procrustes Analysis was performed on free-choice profiling data, which resulted in three significant principal axes. The first principal axis was characterized by overall intensity and sourness, the second by vinegar and saltiness, and the third by astringency.

Mechanisms of biodegradation of metal-citrate complexes by Pseudomonas fluorescens.

Abstract: Biodegradation of metal-citrate complexes by Pseudomonas fluorescens depends on the nature of the complex formed between the metal and citric acid. Bidentate Fe(III)-, Ni-, and Zn-citrate complexes were readily biodegraded, but the tridentate Cd- and Cu-citrate, and U-citrate complexes were not. The biodegradation of Ni- and Zn-citrate commenced after an initial lag period; the former showed only partial (70%) degradation, whereas the latter was completely degraded. Uptake studies with 14C-labeled citric acid and metal-citrate complexes showed that cells grown in medium containing citric acid transported free citric acid at the rate of 28 nmol min-1 and Fe(III)-citrate at the rate of 12.6 nmol min-1 but not Cd-, Cu-, Ni-, U-, and Zn-citrate complexes. However, cells grown in medium containing Ni- or Zn-citrate transported both Ni- and Zn-citrate, suggesting the involvement of a common, inducible transport factor. Cell extracts degraded Fe(III)-, Ni-, U-, and Zn-citrate complexes in the following order: The cell extract did not degrade Cd- or Cu-citrate complexes. These results show that the biodegradation of the U-citrate complex was limited by the lack of transport inside the cell and that the tridentate Cd- and Cu-citrate complexes were neither transported inside the cell nor metabolized by the bacterium.

Graft polymerization of acrylic acid onto starch using potassium permanganate acid (redox system)

Abstract: Graft polymerization of acrylic acid (AA) onto rice starch using postassium permanganate/acid redox system as initiator was investigated. When starch was reacted with KMnO4 solution, MnO2 was deposited onto starch. The dependence of MnO2 amount deposited was directly related to KMnO4 concentration. Subjecting the MnO2-containing starch to a solution consisting of monomer (AA) and acid (citric, tartaric, oxalic and hydrochloric acid) formed poly(AA)–starch graft copolymers. The graft yield, expressed as meq COOH/100 g starch, was measured by the amount of MnO2 deposited, AA concentration, material-to-liquor ratio, kind and concentration of acid, as well as temperature and duration. Finally, the newly prepared poly(AA)–starch graft copolymers were applied to cotton textiles to determine their suitability as sizing agents. The highest graft yield was obtained with citric acid and the least with hydrochloric acid, with tartaric and oxalic acid in between. The graft yield increased by increasing the concentration of acid to a certain concentration beyond which grafting leveled off. A similar trend was observed when the magnitude of grafting was related to the amount of MnO2 deposited. The graft yield increased by increasing the polymerization temperature from 30° to 50°C. Increasing the temperature to 60°C is accompanied by decreased grafting. On the other hand, fabric samples sized with poly(AA)–starch graft copolymers acquire higher tensile strength, elongation at break, and abrasion resistance than that sized with native rice starch, i.e., poly(AA)–starch graft copolymers serve as good sizing agents for cotton textiles. A tentative mechanism for grafting rice starch with AA using the KMnO4/acid redox system was elucidated. © 1995 John Wiley & Sons, Inc.

Increased urinary excretion of analogs of Krebs cycle metabolites and arabinose in two brothers with autistic features.

Abstract: A marked increase in analogs of Krebs cycle metabolites was found in the urine of two brothers with autistic features. These metabolites included citramalic, tartaric (3-OH-malic), and 3-oxoglutaric acids and compounds tentatively identified as a citric acid analog and partially identified as a phenylcarboxylic acid by the fragmentation pattern of the trimethylsilyl (TMS) derivatives of the compounds and mass shifts of the same compounds derivatized with perdeuterated N,O-bis(trimethylsilyl)trifluoroacetamide. The molecular mass of the TMS derivative of the tentatively identified citric acid analog was 596 Da, based on a finding of a significant M - 15 ion at m/z 581. The citric acid analog was excreted in quantities as high as 137 mmol/mol creatinine, based on the response factor of citric acid as a surrogate calibrator. A carbohydrate with a retention time and mass spectrum identical to arabinose was also found in high concentrations in the urine of these brothers.

Pineapple waste - a novel substrate for citric acid production by solid-state fermentation

Abstract: Citric acid production in solid-state fermentation by Aspergillus foetidus ACM3996 was better on pineapple waste than on apple pomace, wheat bran or rice bran The highest citric acid content achieved on pineapple waste was 161 g per 100 g dried pineapple waste, with a moisture content of 70% and in the presence of 3% methanol This represents a yield of 624% based on the sugar consumed

Citric acid in tomato plant roots and its effect on cadmium uptake and distribution

Abstract: Experiments were carried out to investigate the effects of root citric acid on uptake and initial distribution of cadmium (Cd) in tomato plants (Lycopersicon esculentum, cv. Tiny Tim). Cd was measured by γ-spectrometry, using 115Cd spikes. Citric acid was measured by UV-detection, and, after spiking with 14C-citric acid, by β-spectrometry. Cd was applied for 48 h periods, in control experiments, in the presence of citric acid, and after 24 h plant pre-incubation with citric acid. Pre-incubation resulted in two-fold increases in fast-exchangeable amounts of root citric acid, as measured by the presence of citric acid in xylem exudates of decapitated and pressurized roots. Simultaneous application of Cd and citric acid did not change Cd accumulation in total plants and in the roots, nor did any significant change occur with respect to Cd root-to-shoot transport, and Cd concentrations in shoot tissues and xylem fluid. After citric acid pre-incubation, total plant uptake of Cd increased twofold, without any significant change in Cd accumulation in the roots. Cd root-to-shoot transport was increased 5–6 fold, and Cd concentrations in shoot tissues and xylem fluid were increased 6–8 fold. Speciation calculations indicated that, under the conditions applied, xylem Cd may be, at least partly, complexed in citric acid. A C Borstlap Section editor

Diaper rash lotion impregnated sheet

Abstract: A diaper or diaper is impregnated with a skin lotion containing a linear polydimethylsilorane polymer, a non-ionic emulsifier consisting of polyoxyethylene sorbitan fatty acid esters, sorbitan fatty acid esters, polyoxyethylene alcohols, or polyoxyethylene fatty ethers, aloe vera, an alkoxylated ether/ester, sodium citrate, citric acid, a blend of propylene glycol, diazolidinyl urea, methyl paraben, and propyl paraben, and water. Most preferably, the buffering system results in the lotion having a pH of about 5.2 which neutralizes acidic and basic byproducts of urine and fecal matter.

Enzyme Basis for pH Regulation of Citrate and Pyruvate Metabolism by Leuconostoc oenos

Abstract: Citrate and pyruvate metabolism by nongrowing cells of Leuconostoc oenos was investigated. (sup13)C nuclear magnetic resonance (NMR) spectroscopy was used to elucidate the pathway of citrate breakdown and to probe citrate or pyruvate utilization, noninvasively, in living cell suspensions. The utilization of isotopically enriched substrates allowed us to account for the end products derived from the metabolism of endogenous reserves. The effect of environmental parameters, e.g., pH, gas atmosphere, and presence of malate, on the end products of citrate utilization was studied. Approximately 10% of the citrate supplied was converted to aspartate which remained inside the cells. A metabolic shift with pH was observed, with acetoin production being favored at pH 4, whereas lactate and acetate production increased significantly at higher pH values. The information obtained with NMR was complemented with studies on the relevant enzyme activities in the metabolic pathway of citrate breakdown. The intracellular pH of the cells was strongly dependent on the external pH; this result, together with the determination of the pH profile of the enzymic activities, allowed us to establish the basis for pH regulation; lactate dehydrogenase activity was optimal at pH 7, whereas the acetoin-forming enzymes displayed maximal activities below pH 5. Citrate utilization was also monitored in dilute cell suspensions for comparison with NMR experiments performed with dense suspensions.

Heated Ascorbic/Citric Acid Solution as Browning Inhibitor for Pre-Peeled Potatoes

Abstract: Treatment of pre-peeled potatoes with heated ascorbic acid (AA)/citric acid (CA) solution to extend shelf-life was investigated. Potatoes were abrasion or high pressure steam peeled, heated for 5-20 min in 1% AA + 2% CA at 45-55°C, cooled, and then dipped for 5 min in browning inhibitor (BI) solution containing 4% AA + 1% CA + 1% sodium acid pyrophosphate. Combined treatment inhibited potato discoloration for 14 days at 4°C, compared to 3-6 days with BI treatment alone. Raw material and treatment conditions were selected to minimize graying and textural abnormalities encountered with some treatments. Treatment with heated AA/CA may be an alternative to use of sulfites to control browning in pre-peeled potatoes.

The control of polyphenol oxidase activity in fruits and vegetables. A study of the interactions between the chemical compounds used and heat treatment.

Abstract: Objective of this research was to find alternative methods for the control of polyphenol oxidase (PPO) activity in fruits and vegetables with the purpose of reducing or eliminating the use of SO2 for this purpose. Interactions between the use of ascorbic acid, citric acid, EDTA, sodium metabisulphite and heat treatment (70 degrees C for 2 min) in the control of PPO activity were studied in avocado (var. Fortuna), banana (var. Nanica), apple (var. Ana, Fuji, Gala & Golden), pear (var. D'Agua), peach (var. Real), potato (var. Bintje), eggplant (var. Super F100), mushroom (Agaricus bisporus) and hearts-of-palm (Euterpe edulis Mart). The results demonstrated that PPO of avocado and eggplant was most resistant to inhibition by the methods used. The least efficient method tested for the control of PPO was the addition of ascorbic acid and EDTA, while the most efficient methods investigated included the use of ascorbic acid, citric acid, sodium metabisulphite and heat treatment. The results indicated that, with the exception of PPO from avocado, the most adequate alternative method to substitute for the use of SO2 in the control of PPO was a combination of ascorbic acid, citric acid and heat treatment.

Citric acid and polyols production by Aspergillus niger at high glucose concentration in solid state fermentation on inert support

Abstract: Aspergillus niger cultures at high initial glucose concentration (up to 400 g/1) on Amberlite as inert support were carried out. Citric acid was accumulated in the support showing high concentration (94.54 g/l) and productivity (1.35 g/l h) without inhibition related to the presence of metals (Mn2+, Zn2+, Co2+, Cu2+, and Ca2+) at high concentrations. Citric acid accumulation was clearly associated with both, glycerol production and to the age of the culture. Glycerol and erythritol, the major osmoregulator metabolites, were also produced (8.16 and 24.57 g/l respectively) at 400 g/l of glucose.

Activity of p-aminobenzoic acid compared with other organic acids against selected bacteria.

Abstract: The antibacterial activity of p-aminobenzoic acid against Listeria monocytogenes, Salmonella enteritidis and Escherichia coli was compared with the activity of commonly used acidulants: formic, propionic, acetic, lactic and citric acids. Viable count evaluations and MIC determinations indicated that p-aminobenzoic acid caused greater inhibitory effects than the other organic acids. The activity of p-aminobenzoic acid on the growth of the test organisms at selected pH values indicated that p-aminobenzoic acid was more active at low pH than at high pH. Uptake studies showed that the uptake of p-aminobenzoic acid by E. coli was markedly decreased as the pH values increased. Electron micrographs of E. coli cells grown in the presence of p-aminobenzoic acid indicate that p-aminobenzoic acid caused marked damage to the cell envelope. It is suggested that p-aminobenzoic acid has at least two mechanisms of action: one mechanism in common with other organic acids and the other mechanism by interfering with the synthesis of the peptidoglycan layer by an action on the dihydrofolate reductase enzyme.

Efficacy of oral citrate administration in primary hyperoxaluria

Abstract: Urinary citrate is a potent inhibitor of calcium oxalate (CaOx) crystallization, but oral citrate has rarely been used in patients with primary hyperoxaluria (PH). We studied the effect of sodium citrate administration (0.1-0.15 g/kg/day) on urinary citrate excretion and CaOx saturation in seven paediatric patients and the clinical response to long-term treatment (average 4 years) in five patients. Urinary citrate increased from 0.73 to 2.54 mmol/24 h/1.73 m2 and urinary saturation for CaOx (calculated by equil 2) decreased from 11.41 to 6.79 (for both, p < 0.02). Long-term administration of alkali citrate [0.15 g (0.5 mmol)/kg/day] resulted in stable or improved renal function in three and slow deterioration in two partially non-compliant patients. Alkali citrate is effective in patients with PH.

Acid-spray regreening of kiwifruit leaves affected by lime-induced iron chlorosis

Abstract: Kiwifruit (Actinidia deliciosd) vines suffer iron chlorosis when growing in a calcareous soil and symptoms occur despite the presence of medium-to-high concentrations of leaf iron, suggesting the presence of a mechanism that immobilize Fe in plant tissues. In the present study we found a negative correlation between the leaf pH and the chlorophyll concentration in leaves of kiwi vines showing different degrees of chlorosis in calcareous soil and then investigated the effects of acid sprays on chlorotic leaves of kiwi grown in a markedly calcareous soil. The following solutions were sprayed three times at five- and six-day intervals on separate shoots of the same plant (three plants in total): citric acid (2000 mg L-1 and 6000 mg L-1 ), sulphuric acid (38 mg L-1 ), Fe-DTPA ( 130 mg L-1) and deionized water (control). At the end of the trial (19 days from the beginning of treatment application), Fe-chelate caused the most intensive regreening, followed by citric acid (both rates); sulphuric acid caused only a slight increase of leaf chlorophyll as compared to control. The pH of leaves treated with citric but not with sulphuric acid decreased by about 0.2 units as compared to control. Iron-chelate resulted in the greatest increase of both active (extracted by ferrozine) and total iron. The leaves treated with citric acid at both rates also increased their active iron content by about 50% as compared to control leaves. These findings support that high leaf apoplastic pH of plants in calcareous soil is somehow responsible for Fe immobilization and its physiological deficiency.

Growth and Metabolism of Selected Lactic Acid Bacteria in Synthetic Wine

Abstract: A chemically defined synthetic wine was used to study the growth and metabolism of selected lactic acid bacteria (LAB). Leuconostoc oenos 122 and 252 grew well at initial pH 4.0 and 3.2. Pediococcus parvulus 93 and Lactobacillus plantarum 49 also grew well at initial pH 4.0, but were inhibited at initial pH 3.5. A variety of sugars (pentoses, hexoses, and disaccharides) were utilized by leuconostocs and Lb. plantarum, but only mannose, glucose, and trehalose were fermented by Pd. parvulus. Glucose and trehalose were preferentially utilized over other sugars by leuconostocs at initial pH 4. Polyols, including tetriols, pentitols, and hexitols, were formed by all strains at initial pH 4. The polyol mannitol, however, was utilized by Lb. plantarum. Sugar utilization was greatly decreased and polyol formation (except mannitol) was not observed with leuconostocs at pH 3.2. L-Malic acid was metabolized by all strains with the formation of lactic acid. Citric acid was also degraded by the strains studied except for Pd. parvulus. L-Arginine was degraded by leuconostocs only with the production of ornithine and ammonia at pH 4, but not at pH 3.2. L-Malic acid, citric acid and L-arginine could not support growth of any LAB without the presence of a fermentable carbohydrate. This study highlights the need for more basic research on the metabolism of wine LAB.

Buffy-coat-derived platelet concentrates prepared from half-strength citrate CPD and CPD whole blood units. Comparison between three additive solutions: In vitro studies

Abstract: The in vitro effects of storage of platelets prepared from 4 or 6 pooled buffy coat (BC) units and stored in a platelet storage medium consisting of 30-40% of CPD plasma or alternatively half-strength citrate CPD (0.5 CPD) plasma and 60-70% of different alternative platelet additive solutions (PASs) were evaluated. Measurements of mean platelet volume, pH, pO2, pCO2, bicarbonate, glucose, lactate, ATP, total adenine nucleotide content, extracellular lactate dehydrogenase or adenylate kinase activity, as markers for disintegration of platelets, and extracellular beta-thromboglobulin, as a marker for activation of platelets, were included in the in vitro studies. Previous studies indicated that a reduction of the citrate concentration from the standard 21 to 8 mmol/l is associated with a significant reduction of the consumption of glucose and production of lactate. Alternatively, similar effects can be obtained by the addition of acetate. In a preliminary paired study, the effects of different concentrations of acetate were tested. In an additional paired study, the effects of CPD plasma in combination with either saline or a PAS containing NaCl (115.5 mmol/l), citrate (10 mmol/l), and acetate (30 mmol/l), pH 7.2 (PAS-2) were evaluated. 0.5CPD plasma in combination with either PAS-2 or a nonacetate PAS (PAS-1) were also tested. The storage of platelets in 0.5CPD plasma was used as a reference. The conclusions are: (1) A minimum acetate concentration of 30 mmol/l is needed to counteract the effects of citrate on the production of lactate. (2) pH and the bicarbonate buffering capacity are significantly better maintained in PAS-2 than in PAS-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Chewing gum composition with fluoride and citric acid

Abstract: This patent deals with a chewing gum which possesses fluoride and citric acid for improved dental health. The incorporation of fluoride and citric acid into our gum product is for the citric acid to provide a means by which fluoride can be absorbed into the tooth structure. The mechanism of action of this product is the following: citric acid is incorporated in this chewing gum to microscopically open up the pores (prism layers) of the enamel tooth structure. This opening of the pores, at the tooth surface, enables greater contact and penetration of the fluoride to be absorbed into the enamel. The resultant effect is greater penetration of fluoride into the enamel and the underlying tooth structure (dentine). In addition to facilitating the penetration of fluoride into the tooth, there would be an added benefit from the dietary content of the citrus fruits. Moreover, this gum includes novel organoleptic properties as a result of natural sugars, together with enhanced flavor, for sweetness impact.

Spectrophotometric determination of ascorbic acid and dehydroascorbic acid.

Abstract: We present a method for measuring ascorbic acid in methanol/trichloroacetic acid extracts prepared from human plasma after enzymatic oxidation of ascorbic acid to dehydroascorbic acid by ascorbate oxidase. Samples were assayed by spectrophotometrically monitoring the kinetics of the concentration-dependent absorbance changes of dehydroascorbic acid with phosphate-citrate-methanol buffers. Ascorbic acid was determined as the difference between dehydroascorbic acid and total ascorbic acid content. The detection limit was 0.995) over the range 0-1000 mumol/L. Analytical recovery of ascorbic acid added to plasma was 93-105%. The between-day variance was < 7%. Comparison of the spectrophotometric determination (y) with a chromatographic procedure (x) gave y = 1.02x - 0.653 (Sylx = 3.61) over the range of physiologically relevant concentrations. Total analysis time is < 10 min per sample and allows the simultaneous analysis of multiple samples.

Calcium fortified beverages

Abstract: Calcium fortified acid beverages. The calcium source is a combination of calcium hydroxide and calcium glycerophosphate and the acidulant is a combination of citric acid and fumaric acid.

Incomplete operation of biosynthetic and bioenergetic functions of the citric acid cycle in multiple auxotrophic lactobacilli

Abstract: Many of the putative enzymes mediating oxidative reactions of the citric acid cycle were measured in cell-free extracts of Lactobacillus plantarum ATCC 8014, L. casei ATCC 7469, L. helveticus ATCC 15009, and L. acidophilus ATCC 11506. The activities of citrate synthase and aconitase were demonstrated in all the strains investigated. None of isocitrate dehydrogenase, 2-oxoglutarate dehydrogenase, and succinate dehydrogenase activities were detected in any of the strains tested. Fumarase and malate dehydrogenase activities could be detected in some but not all of the strains. On the other hand, all the strains had the activities of fumarase and malate dehydragenase when measured in the direction of reductive reactions of the cycle. In addition, the activities of fumarate reductase and citrate lyase were found in all the strains and in most strains, respectively. All these results suggest that the oxidative pathway in the citric acid cycle serving both bioenergetic and 2-oxoglutarate biosynthetic functions i...