Dimethyl Dicarbonate Research Articles

High Pressures in Combination with Antimicrobials To Reduce Escherichia coli O157:H7 and Salmonella Agona in Apple Juice and Orange Juice

The effect of high pressure processing in conjunction with the chemical antimicrobials, dimethyl dicarbonate (DMDC), hydrogen peroxide, cinnamic acid, potassium sorbate, and sodium benzoate (NaB) on E. coli O157:H7 strain E009 and Salmonella enterica serovar Agona was investigated in apple juice and orange juice, respectively. Juices were inoculated with approximately 106 CFU/ml and subjected to pressures of 550 MPa (E. coli O157:H7 samples) and 400 MPa (Salmonella Agona samples) for 2 min at 6°C (initial temperature). Populations of each pathogen were determined before pressurization, immediately after pressurization, and after samples had been held after treatment for 24 h at 4°C. The most effective treatment for E. coli O157:H7, as determined by plating immediately after pressurization, was 125 ppm of DMDC, which caused a >4.98-log reduction. Other treatments that were significantly different from the sample with no added antimicrobial were 62.5 ppm of DMDC, 300 ppm of hydrogen peroxide, and 500 ppm of NaB, which produced 4.97-, 5.79-, and 3.91-log total reductions, respectively. After 24 h at 4°C, E. coli O157:H7 was undetectable in all treatment groups (and controls). In samples inoculated with Salmonella, the most effective treatment was 62.5 ppm of DMDC, which produced a 5.96-log decrease immediately after pressure treatment. The results for 1,000 ppm of NaB, which produced a 3.26-log decrease, also were significantly different from those for the sample containing no antimicrobials. After 24 h at 4°C, all samples with added antimicrobials had near or more than a 5-log total reduction of Salmonella Agona.

Evaluation of the inhibitory effect of dimethyl dicarbonate (DMDC) against wine microorganisms

Several microbial species associated with wine were challenged against increasing concentrations of dimethyl dicarbonate (DMDC). The concentration inducing complete cell death upon addition to red wine was regarded as the minimum inhibitory concentration (MIC). In dry red wines with 12% (v/v) ethanol and pH 3.50, the inactivation depended on the initial cell concentration. For an initial inoculum of 500 CFU/ml, the MIC of the yeasts species Schizosaccharomyces pombe, Dekkera bruxellensis, Saccharomyces cerevisiae and Pichia guilliermondii was 100 mg/l. The most sensitive strains belong to Zygosaccharomyces bailii, Zygoascus hellenicus and Lachancea thermotolerans, with MIC of 25 mg/l DMDC. For inoculation rates of about 10 6 CFU/ml, the maximum dose of DMDC legally authorised (200 mg/l) was not effective against the most resistant species. The addition of 100 mg/l potassium metabisulphite (PMB), equivalent to 1 mg/l molecular sulphur dioxide, increased the inactivation effect of 100 mg/l DMDC over initial yeast populations of 10 6 CFU/ml but did not fully kill S. pombe and S. cerevisiae. Lactic acid and acetic acid bacteria were not killed by the addition of 300 mg/l of DMDC. Trials performed in wines before bottling showed that in most samples indigenous bacterial populations were not affected by 200 mg/l DMDC. Therefore, under winery practice, DMDC at the maximum dose legally permitted may be regarded as an efficient preservative to control low contamination rates of yeasts but ineffective against lactic acid and acetic acid bacteria.

Inactivation of Escherichia coli O157:H7 and Salmonella in Apple Cider and Orange Juice Treated with Combinations of Ozone, Dimethyl Dicarbonate, and Hydrogen Peroxide

: Inactivation of Escherichia coli O157:H7 and Salmonella in apple cider and orange juice treated with ozone in combination with antimicrobials was evaluated. E. coli O157:H7 or Salmonella was suspended in cider and orange juice, and ozone was pumped into juices (4°C) containing dimethyl dicarbonate (DMDC; 250 or 500 ppm) or hydrogen peroxide (300 or 600 ppm) for up to 90 min (study 1) or 60 min followed by 24-h storage at 4°C (study 2). Study 1: No combination of treatments resulted in a 5-log colony-forming units (CFU) /mL reduction of either pathogen. Study 2: All combinations of antimicrobials plus ozone treatments, followed by refrigerated storage, caused greater than a 5-log CFU/mL reduction, except ozone/DMDC (250 ppm) treatment in orange juice. Ozone treatment in combination with DMDC or hydrogen peroxide followed by refrigerated storage may provide an alternative to thermal pasteurization to meet the 5-log reduction standard in cider and orange juice.

Pd‐Catalyzed Synthesis of Functionalized Arylketones from Boronic Acids and Carboxylic Acids Activated in situ with Dimethyl Dicarbonate.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Fermentability of grape must after inhibition with dimethyl dicarbonate (DMDC).

Dimethyl dicarbonate (DMDC) was added to grape must and to synthetic media and results showed that, at 20 degrees C, 150 mg.L(-)(1) DMDC completely inhibited the fermentation of a grape must that was previously inoculated with 10(6) cells.mL(-)(1) Saccharomyces bayanus and Saccharomyces uvarum. Brettanomyces intermedius, Candida guilliermondii, Hansenula jadinii, Hansenula petersonii, Kloeckera apiculata, Pichia membranaefaciens, and Saccharomyces cerevisiae were inhibited by 250 mg.L(-)(1). Candida valida was inhibited in the presence of 350 mg.L(-)(1), whereas Hanseniaspora osmophila, Saccharomycodes ludwigii, Schizosaccharomyces pombe, and Zygosaccharomyces bailii required 400 mg.L(-)(1). Delay of fermentation (but not inhibition) was noted in the presence of 400 mg.L(-)(1) for the following cultures: Brettanomyces anomalus, Hanseniaspora uvarum, Metschnikowia pulcherrima, Schizosaccharomyces japonicus, Torulaspora delbrueckii, and Zygosaccharomyces florentinus. Acetobacter aceti and Lactobacillus sp. were completely inhibited using 1000 and 500 mg.L(-)(1) DMDC, respectively. The fermentation of a grape must inoculated with 10(6) cells.mL(-)(1) of different wine yeasts was delayed for 4 days after the prior addition of 200 mg.L(-)(1) of DMDC; 200 mg.L(-)(1) DMDC did not show any residual inhibitory effect after 12 h, nor did 300 mg.L(-)(1) 24 h after the addition. In cellar experiments, indigenously contaminated grape musts (with and without skins) showed a delay in fermentation of 48 h after the addition of only 50 mg.L(-)(1) DMDC. The possibility of using DMDC (as pure grade as commercially available) in grape must as a disinfectant for the decontamination of musts indigenously contaminated with wild yeast should be considered seriously, despite its apparent low solubility in water.

Palladium-Catalyzed Direct Conversion of Carboxylic Acids into Ketones with Organoboronic Acids Promoted by Anhydride Activators

Abstract Various carboxylic acids are catalytically converted into ketones on treatment with organoboron compounds in the presence of activators and palladium catalysts. Detailed examination of factors influencing the yield of ketone formation revealed the following characteristics of the reactions: (a) Palladium complexes containing tertiary phosphine ligands, particularly triphenylphosphine and tricyclohexylphosphine, are most effective among the palladium complexes; (b) Dioxane and THF are suitable as the solvent; (c) Dimethyl dicarbonate is required as the activator to obtain ketones in high yields. The process provides a general, versatile, synthetic method to produce various symmetrical and unsymmetrical ketones with aromatic, aliphatic, and heterocyclic groups. The mechanism proposed for the catalytic process involves (i) exchange reaction of the carboxylic acid employed with dimethyl dicarbonate added as the activator to form a mixed anhydride of the carboxylic acid and mono methyl ester of carbonic acid; (ii) oxidative addition of the mixed anhydride to zerovalent palladium species to give an (acyl)(methyl carbonato)palladium species; (iii) decarboxylation of the methyl carbonato ligand to give (acyl)(methoxo)palladium species; (iv) transmetallation of the (acyl)(methoxo)palladium species with an arylboronic acid to give an (acyl)(aryl)palladium species; and (v) reductive elimination of the (acyl)(aryl)palladium species to liberate the coupling product of the acyl and aryl ligands with regeneration of the Pd(0) species. Not only homogeneous catalyst systems but also heterogeneous systems were found to give ketones under mild conditions. On the basis of the present study involving the acyl(methoxo)palladium complexes generated in the reaction mixture of carboxylic acids with dimethyl dicarbonate on reaction with Pd(0) complexes, we also developed a new catalytic process to convert carboxylic acids with terminal alkynes into α, β-alkynyl ketones under similar conditions.

Pd-Catalyzed Synthesis of Functionalized Arylketones from Boronic Acids and Carboxylic Acids Activated in situ with Dimethyl Dicarbonate

Highly efficient catalyst systems were developed that allow the palladium-catalyzed cross-coupling of arylboronic acids with carboxylic acids activated in situ with dimethyl dicarbonate at room temperature. As byproducts,only methanol, CO 2 , and boric acid are formed, making the isolation of the products particularly easy. Thus, many functionalized ketones are conveniently accessible from boronic and carboxylic acids in the presence of 1.5 equivalents of dimethyl dicarbonate and Pd(OAc) 2 -P(p-MeOPh) 3 as the catalyst. The presence of small amounts of water and a ligand-Pd ratio lower than 4 is crucial for achieving good yields at low temperatures.

General and Greener Route to Ketones by Palladium-Catalyzed Direct Conversion of Carboxylic Acids with Organoboronic Acids

Abstract Cross-coupling reaction of carboxylic acids with organoboron compounds catalyzed by palladium complexes in the presence of an activator such as dimethyl dicarbonate under mild conditions gives ketones in excellent yields except for certain substrates.

Survival of Escherichia coli O157:H7 in Apple Cider as Affected by Dimethyl Dicarbonate, Sodium Bisulfite, and Sodium Benzoate

ABSTRACTSurvival of Escherichia coli O157:H7 in apple cider containing no preservatives, 0.025% dimethyl dicarbonate (DMDC), 0.045% sodium benzoate (SB), 0.0046% sodium bisulfite (NaS; 65.5% sulfur dioxide), or a combination of NaS and SB (NaS/SB) and stored at 4, 10, and 25°C was evaluated. E. coli O157:H7 survived for up to 18 days at 4,10, and 25°C in unpreserved apple cider. At 4 and 10°C, DMDC was most efficient at inactivating E. coli O157:H7, generally followed by NaS/SB SB, and NaS (p<0.05). E coli O157:H7 was more resistant to preservatives at 4°C than at 25°C (P < 0.05). E. coli O157:H7 was sublethally injured in cider containing preservatives, and to a lesser extent, in unpreserved cider. Generally, injury was more pronounced in cider containing DMDC, followed by NaS/SB, SB, and NaS (p<0.05).

Citric Acid and Antimicrobials Affect Microbiological Stability and Quality of Tomato Juice

ABSTRACTAcidification, addition of dimethyl dicarbonate and a mixture of potassium sorbate and sodium benzoate and storage temperature were related to microbiological stability and quality of tomato juice. Whether iuices were acidified CDH 4.0 to 3.7) or nonacidified. dimethyl dicarbonate and sorbate/benzoate were highly effective in diminishcng mold and yeast count at 5°C and 20°C. Dimethyl dicarbonate in juices acidified to pH 3.7 and stored at 5°C was most effective in controlling plate counts, followed by sorbate/benzoate in juices acidified to pH 3.7 and stored at 5°C and 20°C. Tomato juice treated with dimethyl dicarbonate had lower amounts of ascorbic acid, total amino acids, fructose, glucose, lycopene and β‐carotene.

The vibrational spectra, structure, and conformational behavior of dimethyl dicarbonate

The IR spectra of the liquid and solid states and the Raman spectrum of the liquid state of dimethyl dicarbonate (DMDC) have been obtained. Comparison of liquid and solid-state spectra indicate that in the liquid state DMDC is an equilibrium mixture of at least two conformers. Raman depolarization ratios, electrostatic repulsion considerations, and the ratio of the area of the two carbonyl stretching bands provide a basis for suggesting that the primary DMDC structure in the liquid state possesses C 2 point group symmetry. Based on this evidence and assignments of analogous molecules, a tentative vibrational assignment is proposed.

The Interaction of Sulfur Dioxide, pH, and Dimethyl Dicarbonate on the Growth ofSaccharomyces cerevisiaeMontrachet andLeuconostoc oenosMCW

Wine yeast <i>Saccharomyces cerevisiae</i> Montrachet and malolactic bacteria <i>Leuconostoc oenos</i> MCW were grown in and acclimatized to wine with significant amounts of sulfur dioxide. The cultures were transferred to wine at different pH levels with varying amounts of SO₂ and dimethyl dicarbonate (DMDC). Both compounds were inhibitors to yeast and bacteria growth, and there was a synergistic activity between them. With a free SO₂ level of 25 mg/L and the addition of 50 mg/L DMDC, control of the yeast and the bacteria was excellent at pH 3.6 or lower in a sweet white table wine and a dry red table wine.

The Effects of Ethanol, Temperature, and Dimethyl Dicarbonate on Viability ofSaccharomyces CerevisiaeMontrachet No. 522 in Wine

Dimethyl dicarbonate (DMDC) was added at several levels to a sweetened (2g/100 mL) table wine with concentrations of 8% and 10% v/v ethanol respectively that had been inoculated with <i>Saccharomyces cerevisiae</i> Montrachet No. 522. The wine was subjected to varying temperatures ranging from 5°C to 30°C. It was found that the higher ethanol concentration in conjunction with the higher temperatures (20°C and 30°C) were most effective in the rate and completeness of sterilization of this yeast in the media. At higher temperatures the effect of heat-alcohol sterilization became dominant.

Influence of pH and Ethanol on the Effectiveness of Dimethyl Dicarbonate in Controlling Yeast Growth in Model Wine Systems

The effects of pH and ethanol content on the ability of dimethyl dicarbonate to control yeast refermentation were examined in model wine systems. This study showed that decreasing pH and increasing ethanol levels favored the sterilant action of DMDC.

Measurement of methylcarbamate formed by the addition of dimethyl dicarbonate to model solutions and to wines.

Measurement of methylcarbamate formed by the addition of dimethyl dicarbonate to model solutions and to wines.

Formation of Methanol and Ethyl Methyl Carbonate by Dimethyl Dicarbonate in Wine and Model Solutions

Dimethyl dicarbonate (DMDC) has been proposed as a possible alternative to diethyl dicarbonate as a cold sterilant for use in packaging alcoholic beverages. Some of the breakdown products of this agent (known commonly as dimethyl pyrocarbonate) were measured in wine and model solutions. Methanol produced by hydrolysis of DMDC was measured by gas chromatographic analysis of distillates. The levels produced were linear with dose and in the 50-mg/L range for normal doses. A gas chromatographic procedure was adapted for analysis of ethyl methyl carbonate formed from the DMDC reaction with ethanol. The product formation was linear with substrate concentrations and in the low mg/L range. This procedure for analysis of ethyl methyl carbonate is proposed as a method for the detection and quantification of DMDC addition to alcoholic beverages.