Independent Effects of Acetic Acid and pH on Survival ofEscherichia coli in Simulated Acidified Pickle Products†‡

2004 ◽  
Vol 67 (1) ◽  
pp. 12-18 ◽  
Author(s):  
F. BREIDT ◽  
J. S. HAYES ◽  
R. F. McFEETERS
Keyword(s):  
Acetic Acid ◽  
Organic Acids ◽  
Acid Resistance ◽  
Ofescherichia Coli ◽  
Acid Solutions ◽  
Specific Effects ◽  
Effects Of Ph ◽  
Ph Range ◽  
Independent Effects ◽  
D Values

Our objective was to determine the effects of organic acids and pH on the rate at which selected strains ofEscherichia coli O157:H7 die in acid solutions representative of acidified pickle products (pH < 4.6). We used gluconic acid/sodium gluconate (pKa = 3.7) as a noninhibitory buffer to maintain pH at selected values in the absence of other organic acids. This was possible because we found that the inhibitory effects of this acid onE. coli strains at pH 3.1 were independent of acid concentration over a range of 2 to 200 mM. By this method, the lethal effects of acetic acid solutions (100 to 400 mM) at selected pH values between 3.1 and 4.1 were compared with the effects of pH alone (as determined using gluconate buffer). We found D-values were two- to fourfold lower with acetic acid compared with the effect of pH alone for simulated pickle brines in this pH range. Glutamic acid, an amino acid that is known to enhance acid resistance inE. coli and is a component of pickle brines, protected theE. coli strains from the specific effects of acetic acid.

scholarly journals Pseudomonas spp.: Are Food Grade Organic Acids Efficient against These Spoilage Microorganisms in Fresh Cheeses?

Foods ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 891
Author(s):  
Erica Tirloni ◽  
Cristian Bernardi ◽  
Simone Stella
Keyword(s):  
Acetic Acid ◽  
Lactic Acid ◽  
Organic Acids ◽  
Brain Heart Infusion ◽  
Life Extension ◽  
Acid Solutions ◽  
Lower Growth ◽  
Control Series ◽  
Pseudomonas Spp ◽  
Original Product

Psychrotolerant Pseudomonas spp. are among the most common spoilage agents in fresh, soft and semi-soft cheeses; therefore, hurdles inhibiting their growth are in strong demand by producers. This study aimed to establish Minimal Inhibiting Concentrations (MICs) of lactic and acetic acid towards P. fluorescens and to evaluate the efficacy of a cheese surface treatment with these two organic acids. MICs were determined in Brain Heart Infusion broth at 30 °C: the inhibition was achieved at a concentration of 49.96 mM and 44.40 mM of acetic and lactic acid, respectively. Two series of inhibition tests were performed on fresh “Primo sale” cheese, inoculated with P. brenneri MGM3, then dipped into different acid solutions (acetic acid: 49.96, 99.92 and 149.88 mM; lactic acid: 44.40, 88.80 and 133.20 mM) and stored at 6 °C. P. brenneri MGM3 were enumerated, including a control series. A significantly lower growth was revealed at the highest concentrations tested, both for acetic (p < 0.01) and lactic acid (p < 0.05) if compared to control samples. A conditioning of “Primo sale” surface with organic acid solutions could be a useful hurdle for Pseudomonas inhibition and shelf-life extension; it should be applied in combination with other mild interventions to fight spoilage and maintain the original product characteristics.

Inactivation of Pseudomonas fluorescens in Skim Milk by Combinations of Pulsed Electric Fields and Organic Acids

2005 ◽  
Vol 68 (6) ◽  
pp. 1232-1235 ◽  
Author(s):  
JUAN J. FERNÁNDEZ-MOLINA ◽  
BILGE ALTUNAKAR ◽  
DANIELA BERMÚDEZ-AGUIRRE ◽  
BARRY G. SWANSON ◽  
GUSTAVO V. BARBOSA-CÁNOVAS
Keyword(s):  
Acetic Acid ◽  
Organic Acids ◽  
Pseudomonas Fluorescens ◽  
Propionic Acid ◽  
Electric Fields ◽  
Skim Milk ◽  
Pulsed Electric Fields ◽  
Treatment Temperature ◽  
Initial Concentration ◽  
Ph Range

Pseudomonas fluorescens suspended in skim milk was inactivated by application of pulsed electric fields (PEF) either alone or in combination with acetic or propionic acid. The initial concentration of microorganisms ranged from 105 to 106 CFU/ml. Addition of acetic acid and propionic acid to skim milk inactivated 0.24 and 0.48 log CFU/ml P. fluorescens, respectively. Sets of 10, 20, and 30 pulses were applied to the skim milk using exponentially decaying pulses with pulse lengths of 2 μs and pulse frequencies of 3 Hz. Treatment temperature was maintained between 16 and 20°C. In the absence of organic acids, PEF treatment of skim milk at field intensities of 31 and 38 kV/cm reduced P. fluorescens populations by 1.0 to 1.8 and by 1.2 to 1.9 log CFU/ml, respectively. Additions of acetic and propionic acid to the skim milk in a pH range of 5.0 to 5.3 and PEF treatment at 31, 33, and 34 kV/cm, and 36, 37, and 38 kV/cm reduced the population of P. fluorescens by 1.4 and 1.8 log CFU/ml, respectively. No synergistic effect resulted from the combination of PEF with acetic or propionic acid.

Influence of Acetic, Citric, and Lactic Acids on Escherichia coli O157:H7 Membrane Lipid Composition, Verotoxin Secretion, and Acid Resistance in Simulated Gastric Fluid†

2005 ◽  
Vol 68 (4) ◽  
pp. 673-679 ◽  
Author(s):  
HYUN-GYUN YUK ◽  
DOUGLAS L. MARSHALL
Keyword(s):  
Acetic Acid ◽  
Lactic Acid ◽  
Organic Acid ◽  
Lipid Composition ◽  
Acid Resistance ◽  
Gastric Fluid ◽  
Membrane Lipid ◽  
Simulated Gastric Fluid ◽  
Membrane Lipid Composition ◽  
D Values

The effect of organic acid (acetic, citric, and lactic acids) adaptation at equivalent initial pH values (6.4 and 5.4) on changes in membrane lipid composition, verotoxin concentration, and acid resistance in simulated gastric fluid (pH 1.5, 37°C) was determined for Escherichia coli O157:H7 ATCC 43895 (HEC) and an rpoS mutant of E. coli O157:H7 ATCC 43895 (RM, FRIK 816-3). For HEC, lactic acid–adapted (pH 5.4) cells had the greatest D-value (32.2 min) and acetic acid–adapted (pH 5.4) cells had the smallest D-value (16.6 min) in simulated gastric fluid. For RM, D-values of citric and acetic acid–adapted cells were similar to those for nonadapted cells grown at pH 7.3, but D-values increased from 13.1 to 27.9 min in lactic acid–adapted cells (from pH 7.3 to pH 5.4). For both strains, the ratio of cis-vaccenic to palmitic acids decreased for citric and lactic acid–adapted cells, but the ratio increased for acetic acid–adapted cells at pH 5.4. Organic acid–adapted cells produced less total verotoxin than did nonadapted cells at approximately 108 CFU/ml. Extracellular verotoxin concentration proportionally decreased with decreasing pH for both HEC and RM. Changes in membrane lipid composition, verotoxin concentration, and acid resistance in HEC and RM were dependent on both pH and organic acid. Deletion of the rpoS gene did not affect these changes but did decrease acid resistance in citric acid–adapted cells. Results indicate that decreased membrane fluidity may have caused increased acid resistance and decreased verotoxin secretion.

Differentiation of the Effects of pH and Lactic or Acetic Acid Concentration on the Kinetics of Listeria Monocytogenes Inactivation

1993 ◽  
Vol 56 (6) ◽  
pp. 474-478 ◽  
Author(s):  
R. L. BUCHANAN ◽  
M. H. GOLDEN ◽  
R. C. WHITING
Keyword(s):  
Acetic Acid ◽  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Acid Concentration ◽  
Brain Heart Infusion ◽  
Acetic Acid Concentration ◽  
Effects Of Ph ◽  
Lag Period ◽  
D Values ◽  
Acetic Acids

The effects of pH and lactic acid or acetic acid concentration on Listeria monocytogenes inactivation were studied in brain heart infusion broth using a three strain mixture. Combinations of lactic acid/sodium lactate and acetic acid/sodium acetate were used to achieve concentrations of 0.1, 0.5, 1.0, and 2,0 M in conjunction with pH values of 4.0, 5.0, 6.0, and 7.0. Cultures adjusted with HCl to pH 3.0 to 7.0 in 0.5 pH unit intervals were used as 0.0 M controls. Each pH/concentration combination was inoculated to a level of 108 CFU/ml and incubated at 28°C for up to 60 d. Bacterial populations were determined periodically by plate counts. Inactivation was exponential after an initial lag period. Survivor curves (log# versus time) were fitted using a linear model that incorporated a lag period. The model was subsequently used to calculate D values and “time to a 4-D (99.99%) inactivation” (t4-D); t4-D values were directly related to pH and inversely related to acid concentration. At acid/pH combinations that supported growth, the level of the organism increased slightly (2- to 10-fold) before declining. In the HCl-adjusted controls with pH's ≤5.5, the rate of inactivation was linearly related to pH. In the presence of the monocarboxylic acids, the duration of the lag period and the rate of inactivation were dependent on the pH, as well as the identity and concentration of acid. 4-D inactivation times were related to the level of undissociated lactic and acetic acids. That relationship was described by the equations, t4-D = exp (−0.1773*LA0.5 + 7.3482) and t4-D = exp (−0.1468*AA0.5 + 7.3905) for lactic and acetic acids, respectively, where LA and AA are mM of undissociated acid. These relationships were used in conjunction with the Henderson-Hasselback equation to develop a model for predicting the rate of inactivation as a function of pH and total organic acid concentration.

Efficient Preconcentration of Cu2+, Zn2+ and Fe3+ with an Agarose-Schiff Base Sorbent

2007 ◽  
Vol 72 (7) ◽  
pp. 908-916 ◽  
Author(s):  
Payman Hashemi ◽  
Hatam Hassanvand ◽  
Hossain Naeimi
Keyword(s):  
Schiff Base ◽  
Metal Ions ◽  
Metal Ion ◽  
Good Accuracy ◽  
Kinetic Studies ◽  
Sample Volume ◽  
Effects Of Ph ◽  
Glass Column ◽  
High Concentrations ◽  
Ph Range

Sorption and preconcentration of Cu2+, Zn2+ and Fe3+ on a salen-type Schiff base, 2,2'- [ethane-1,2-diylbis(nitrilomethylidyne)]bis(2-methylphenol), chemically immobilized on a highly crosslinked agarose support, were studied. Kinetic studies showed higher sorption rates of Cu2+ and Fe3+ in comparison with Zn2+. Half-times (t1/2) of 31, 106 and 58 s were obtained for sorption of Cu2+, Zn2+ and Fe3+ by the sorbent, respectively. Effects of pH, eluent concentration and volume, ionic strength, buffer concentration, sample volume and interferences on the recovery of the metal ions were investigated. A 5-ml portion of 0.4 M HCl solution was sufficient for quantitative elution of the metal ions from 0.5 ml of the sorbent packed in a 6.5 mm i.d. glass column. Quantitative recoveries were obtained in a pH range 5.5-6.5 for all the analytes. The volumes to be concentrated exceeding 500 ml, ionic strengths as high as 0.5 mol l-1, and acetate buffer concentrations up to 0.3 mol l-1 for Zn2+ and 0.4 mol l-1 for Cu2+ and Fe3+ did not have any significant effect on the recoveries. The system tolerated relatively high concentrations of diverse ions. Preconcentration factors up to 100 and detection limits of 0.31, 0.16 and 1.73 μg l-1 were obtained for Cu2+, Zn2+ and Fe3+, respectively, for their determination by a flame AAS instrument. The method was successfully applied to the metal ion determinations in several river water samples with good accuracy.

scholarly journals The metabolic profile of Bifidobacterium dentium reflects its status as a human gut commensal

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Melinda A. Engevik ◽  
Heather A. Danhof ◽  
Anne Hall ◽  
Kristen A. Engevik ◽  
Thomas D. Horvath ◽  
...  
Keyword(s):  
Gastrointestinal Tract ◽  
Metabolic Pathways ◽  
Glycosyl Hydrolase ◽  
Acid Resistance ◽  
Human Gut ◽  
Nutrient Sources ◽  
Metabolic Plasticity ◽  
Defined Media ◽  
High Viability ◽  
Ph Range

Abstract Background Bifidobacteria are commensal microbes of the mammalian gastrointestinal tract. In this study, we aimed to identify the intestinal colonization mechanisms and key metabolic pathways implemented by Bifidobacterium dentium. Results B. dentium displayed acid resistance, with high viability over a pH range from 4 to 7; findings that correlated to the expression of Na+/H+ antiporters within the B. dentium genome. B. dentium was found to adhere to human MUC2+ mucus and harbor mucin-binding proteins. Using microbial phenotyping microarrays and fully-defined media, we demonstrated that in the absence of glucose, B. dentium could metabolize a variety of nutrient sources. Many of these nutrient sources were plant-based, suggesting that B. dentium can consume dietary substances. In contrast to other bifidobacteria, B. dentium was largely unable to grow on compounds found in human mucus; a finding that was supported by its glycosyl hydrolase (GH) profile. Of the proteins identified in B. dentium by proteomic analysis, a large cohort of proteins were associated with diverse metabolic pathways, indicating metabolic plasticity which supports colonization of the dynamic gastrointestinal environment. Conclusions Taken together, we conclude that B. dentium is well adapted for commensalism in the gastrointestinal tract.

Durability of Red Mud Based Geopolymer Paste in Acid Solutions

2016 ◽  
Vol 866 ◽  
pp. 99-105 ◽  
Author(s):  
Smita Singh ◽  
M.U. Aswath ◽  
R.V. Ranganath
Keyword(s):  
Mechanical Properties ◽  
Acetic Acid ◽  
Fly Ash ◽  
Red Mud ◽  
Acetic Acid Solution ◽  
Strength Loss ◽  
Acid Solutions ◽  
Test Results ◽  
Acid Attack ◽  
Geopolymer Paste

The present investigation is on the effect of red mud on the mechanical properties and durability of the geopolymer paste in sulphuric and acetic acid solution. Red mud and fly ash were used to form the geopolymer paste along with the alkalies. The variation of red mud in the paste composition was from 0% to 90%. Cylindrical shaped specimens of 1 inch diameter and 1 inch height were prepared. The specimens were immersed in 5% sulphuric acid and 5% acetic acid for 1, 7, 14, 28, 56 and 84 days and tested for weight loss, visual deformation, strength loss and colour of the solvent, based on the procedure specified by ASTM C 267 – 01. SEM/EDX Tests were performed on the geopolymer specimens. Test results show that initially, the strength of the geopolymer increased upon the addition of red mud. The strength was maximum when the percentage of red mud was 30%. The maximum strength obtained was 38 MPa for the paste containing 30% red mud using 10M alkali solution as against 31.69 MPa, when only fly ash was used. Geopolymer paste containing 30% and 50% red mud showed better resistance to acid attack. The strength loss was minimum for the samples containing 30% red mud in both inorganic and organic acid i.e. sulphuric and acetic acid.

Olivine dissolution at 25°C: Effects of pH, CO2, and organic acids

1991 ◽  
Vol 55 (4) ◽  
pp. 943-954 ◽  
Author(s):  
Roy A Wogelius ◽  
John V Walther
Keyword(s):  
Organic Acids ◽  
Effects Of Ph
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