Interaction of Citric Acid Concentration and pH on the Kinetics of Listeria monocytogenes Inactivation

1994 ◽  
Vol 57 (7) ◽  
pp. 567-570 ◽  
Author(s):  
ROBERT L. BUCHANAN ◽  
MARSHA H. GOLDEN
Keyword(s):  
Listeria Monocytogenes ◽  
Citric Acid ◽  
Acid Concentration ◽  
Brain Heart Infusion ◽  
Citric Acid Concentration ◽  
The Media ◽  
Low Levels ◽  
D Values ◽  
Kinetics Of ◽  
Acetic Acids

The effects and interactions between pH and CitriC acid concentration on the inactivation of Listeria monocytogenes was determined using a three-strain mixture. Citric acid/sodium citrate combinations were added to brain heart infusion (BHI) broth to achieve concentrations of 0.1, 0.5, 1.0 and 2.0 M in conjunction with pH values of 4, 5, 6 and 7. The media were dispensed in 20-ml portions in dilution bottles, inoculated to approximately 108 CFU/ml, and incubated at 28°C. Survivor curves were generated using a linear model incorporating a lag term, and D-values and “time to 4-D inactivation” values were calculated. The results were compared against control cultures in which the pH was modified using hydrochloric acid (HCI). The rate of inactivation was dependent on both the pH and concentration of citric acid. Low levels of citric acid were protective, particularly at pH 5 and 6. At higher concentrations, a distinct anion effect was observed as compared to the HCl controls, with inactivation rates being correlated with the completely undissociated form of the acid. Comparison of the kinetic data with earlier results with lactic and acetic acids suggests that citric acid has both protective and bactericidal activity against L. monocytogenes, which involve different modes of action.

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.

scholarly journals Optimization of Betalain Pigments Extraction Using Beetroot by-Products as a Valuable Source

Inventions ◽  
2021 ◽  
Vol 6 (3) ◽  
pp. 50
Author(s):  
Silvia Lazăr (Mistrianu) ◽  
Oana Emilia Constantin ◽  
Nicoleta Stănciuc ◽  
Iuliana Aprodu ◽  
Constantin Croitoru ◽  
...  
Keyword(s):  
Citric Acid ◽  
Acid Concentration ◽  
Ethanol Concentration ◽  
Extraction Process ◽  
Extraction Time ◽  
Quadratic Model ◽  
Citric Acid Concentration ◽  
Operating Variables ◽  
Conventional Solvent Extraction ◽  
Optimized Conditions

(1) Background: This study is designed to extract the bioactive compounds from beetroot peel for future use in the food industry. (2) Methods: Spectrophotometry techniques analyzed the effect of conventional solvent extraction on betalains and polyphenolic compounds from beetroot peels. Several treatments by varying for factors (ethanol and citric acid concentration, temperature, and time) were applied to the beetroot peel samples. A Central Composite Design (CCD) has been used to investigate the effect of the extraction parameters on the extraction steps and optimize the betalains and total polyphenols extraction from beetroot. A quadratic model was suggested for all the parameters analyzed and used. (3) Results: The maximum and minimum variables investigated in the experimental plan in the coded form are citric acid concentration (0.10–1.5%), ethanol concentration (10–50%), operating temperature (20–60 °C), and extraction time (15–50 min). The experimental design revealed variation in betalain content ranging from 0.29 to 1.44 mg/g DW, and the yield of polyphenolic varied from 1.64 to 2.74 mg/g DW. The optimized conditions for the maximum recovery of betalains and phenols were citric acid concentration 1.5%, ethanol concentration 50%, temperature 52.52 °C, and extraction time 49.9 min. (4) Conclusions: Overall, it can be noted that the extraction process can be improved by adjusting operating variables in order to maximize the model responses.

scholarly journals Development of poly(vinyl alcohol)-based membranes by the response surface methodology for environmental applications

2020 ◽  
Vol 24 ◽  
pp. e5
Author(s):  
Juliana Zanol Merck ◽  
Camila Suliani Raota ◽  
Jocelei Duarte ◽  
Camila Baldasso ◽  
Janaina Da Silva Crespo ◽  
...  
Keyword(s):  
Response Surface Methodology ◽  
Citric Acid ◽  
Response Surface ◽  
Acid Concentration ◽  
Vinyl Alcohol ◽  
Membrane Preparation ◽  
Poly Vinyl Alcohol ◽  
Esterification Reaction ◽  
Citric Acid Concentration ◽  
Ft Ir

The pollution of hydric sources by pharmaceuticals is an issue in many countries, particularly in Brazil. The presence of these substances causes deleterious effects on the environment and human health. One of the main sources of this contamination is domestic sewage, due to the expressive amount of medicines released in their unaltered form. Unfortunately, traditional wastewater treatment is not effective for the removal of pharmaceuticals and, for this reason, membrane technology is an attractive alternative to overcome this issue. In this regard, hydrophilic polymers, such as poly(vinyl alcohol) (PVA), are the most suitable. However, their high affinity with water causes intense swelling, leading to severe modifications in the membrane properties. In view of all these facts, the present work evaluated the swelling of PVA-based membranes, with the aim of finding the membrane preparation method that has the lowest swelling, thereby providing the most suitable characteristics for pharmaceutical removal from wastewater. The membranes were prepared by the casting of a polymeric solution, with PVA as a basis polymer, citric acid as a crosslink agent and glycerol and silver nanoparticles as performance additives. The process optimization was performed using a design of experiments with posterior analysis by the response surface methodology (RSM). The RSM assessed the effect on the membrane swelling of the factors, including citric acid concentration and the time and temperature of crosslinking. The membrane characterization was performed by Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy coupled with a field emission gun (SEM-FEG) and water contact angle (WCA) measurements. Overall, the condition that showed the lowest swelling was obtained with 10% of citric acid and crosslinking for 4 h at 130 °C. Under these conditions, the membrane had a mass swelling of 42% and a dimensional swelling of 24%. Additionally, our statistical analysis revealed that the factors with the dominant effects were the citric acid concentration and the temperature of crosslinking. The FT-IR analysis suggested that the crosslinking occurred by an esterification reaction, as showed by the stretching frequencies of C=O at 1710 cm-1 and ester C-O at 1230 cm-1. Moreover, the SEM-FEG images revealed a smooth and flat surface and a dense cross section with a thickness of ~113 μm. Concerning the WCA, the angle was at ~80°, which is characteristic of hydrophilic materials. Finally, the data suggested that it is possible to optimize the membrane preparation process with adequate properties so that it can be subsequently applied to the removal of pharmaceuticals from hospital wastewater.

Determination of the Thermal Inactivation Kinetics of Listeria monocytogenes, Salmonella enterica, and Escherichia coli O157:H7 and non-O157 in Buffer and a Spinach Homogenate

2015 ◽  
Vol 78 (8) ◽  
pp. 1467-1471 ◽  
Author(s):  
EMEFA ANGELICA MONU ◽  
MALCOND VALLADARES ◽  
DORIS H. D'SOUZA ◽  
P. MICHAEL DAVIDSON
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Salmonella Enterica ◽  
Thermal Inactivation ◽  
Inactivation Kinetics ◽  
Mild Heat ◽  
Log Reduction ◽  
D Values ◽  
Heat Processes ◽  
Kinetics Of

Produce has been associated with a rising number of foodborne illness outbreaks. While much produce is consumed raw, some is treated with mild heat, such as blanching or cooking. The objectives of this research were to compare the thermal inactivation kinetics of Listeria monocytogenes, Salmonella enterica, Shiga toxin–producing Escherichia coli (STEC) O157:H7, and non-O157 STEC in phosphate-buffered saline (PBS; pH 7.2) and a spinach homogenate and to provide an estimate of the safety of mild heat processes for spinach. Five individual strains of S. enterica, L. monocytogenes, STEC O157:H7, and non-O157 STEC were tested in PBS in 2-ml glass vials, and cocktails of the organisms were tested in blended spinach in vacuum-sealed bags. For Listeria and Salmonella at 56 to 60°C, D-values in PBS ranged from 4.42 ± 0.94 to 0.35 ± 0.03 min and 2.11 ± 0.14 to 0.16 ± 0.03 min, respectively. D-values at 54 to 58°C were 5.18 ± 0.21 to 0.53 ± 0.04 min for STEC O157:H7 and 5.01 ± 0.60 to 0.60 ± 0.13 min for non-O157 STEC. In spinach at 56 to 60°C, Listeria D-values were 11.77 ± 2.18 to 1.22 ± 0.12 min and Salmonella D-values were 3.51 ± 0.06 to 0.47 ± 0.06 min. D-values for STEC O157:H7 and non-O157 STEC were 7.21 ± 0.17 to 1.07 ± 0.11 min and 5.57 ± 0.38 to 0.99 ± 0.07 min, respectively, at 56 to 60°C. In spinach, z-values were 4.07 ± 0.16, 4.59 ± 0.26, 4.80 ± 0.92, and 5.22 ± 0.20°C for Listeria, Salmonella, STEC O157:H7, and non-O157 STEC, respectively. Results indicated that a mild thermal treatment of blended spinach at 70°C for less than 1 min would result in a 6-log reduction of all pathogens tested. These findings may assist the food industry in the design of suitable mild thermal processes to ensure food safety.

Inactivation Kinetics of Three Listeria monocytogenes Strains under High Hydrostatic Pressure

2008 ◽  
Vol 71 (10) ◽  
pp. 2007-2013 ◽  
Author(s):  
INEKE K. H. VAN BOEIJEN ◽  
ROY MOEZELAAR ◽  
TJAKKO ABEE ◽  
MARCEL H. ZWIETERING
Keyword(s):  
Listeria Monocytogenes ◽  
Hydrostatic Pressure ◽  
High Hydrostatic Pressure ◽  
Inactivation Kinetics ◽  
Wild Type ◽  
First Order Kinetics ◽  
Survival Capacity ◽  
D Values ◽  
Kinetics Of ◽  
Stable Feature

High hydrostatic pressure (HHP) inactivation of three Listeria monocytogenes strains (EGDe, LO28, and Scott A) subjected to 350 MPa at 20°C in ACES buffer resulted in survival curves with significant tailing for all three strains. A biphasic linear model could be fitted to the inactivation data, indicating the presence of an HHP-sensitive and an HHP-resistant fraction, which both showed inactivation according to first-order kinetics. Inactivation parameters of these subpopulations of the three strains were quantified in detail. EGDe showed the highest D-values for the sensitive and resistant fraction, whereas LO28 and Scott A showed lower HHP resistance for both fractions. Survivors isolated from the tail of LO28 and EGDe were analyzed, and it was revealed that the higher resistance of LO28 was a stable feature for 24% (24 of 102) of the resistant fraction. These HHP-resistant variants were 10 to 600,000 times more resistant than wild type when exposed to 350 MPa at 20°C for 20 min. Contrary to these results, no stable HHP-resistant isolates were found for EGDe (0 of 102). The possible effect of HHP survival capacity of stress-resistant genotypic and phenotypic variants of L. monocytogenes on the safety of HHP-processed foods is discussed.

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