The Measurement of the Activity Coefficient Ratios of Protonated and Neutral Forms of Hammett Indicators in Several Strong Acids

1972 ◽  
Vol 50 (14) ◽  
pp. 2254-2263 ◽  
Author(s):  
T. R. Essig ◽  
J. A. Marinsky
Keyword(s):  
Activity Coefficient ◽  
Linear Relationship ◽  
Water Activity ◽  
Acid Concentration ◽  
Large Range ◽  
Reference Standard ◽  
Neutral Form ◽  
Activity Coefficient Ratio ◽  
Solubility Studies ◽  
Strong Acids

The activity coefficient ratio for several indicators has been estimated for the protonated and neutral forms of the same indicator molecule over a large range of acidity in H2SO4, HClO4, and HCl systems. The activity coefficient (fB) of the neutral form of a number of Hammett indicators was determined via solubility measurements. The observed linear relationship between log fB and [Formula: see text] then permitted estimate by extrapolation of log fB not experimentally accessible for the more basic indicators. Solubility studies of the pentacyanopropenide (PCP−) salts of these more basic protonated indicators were referred to a reference standard, tetraethylammonium pentacyanopropenide (TEA+PCP−) according to the method developed by Boyd to obtain the activity coefficient ratio [Formula: see text] By synthesizing the term [Formula: see text] the approach to a meaningful value of [Formula: see text] is believed to be facilitated. This function is uniquely related to the water activity of the various acid systems examined to support the suggestion by Hammett that [Formula: see text] is a constant for primary aniline indicators at a specified acid concentration.

A Microbiological Assay for Penicillic Acid1

1978 ◽  
Vol 41 (6) ◽  
pp. 432-434 ◽  
Author(s):  
F. J. OLIVIGNI ◽  
L. B. BULLERMAN
Keyword(s):  
Bacillus Subtilis ◽  
Biological Activity ◽  
Thin Layer ◽  
Linear Relationship ◽  
Acid Concentration ◽  
Spore Suspension ◽  
Liquid Media ◽  
Penicillic Acid ◽  
Bioassay Method ◽  
Quantitative Bioassay

Six bactertial cultures were studied in a search for an organism sensitive to penicillic acid suitable for use in a quantitative bioassay of this mycotoxin. A vegetative culture and a commercially prepared spore suspension of Bacillus subtilis were both sensitive to as little as 1 μg of penicillic acid and exhibited a linear relationship between 1 and 100 μg. The bioassay method was comparable in accuracy to thin layer chromatographic assay. The procedure was used to verify the biological activity of sample extracts, as well as to quantitate penicillic acid concentration in samples of liquid media and corn. The bioassay is sensitive, rapid (15–17 h), simple and inexpensive.

scholarly journals Exponentially Increased Thermal Resistance ofSalmonellaspp. andEnterococcus faeciumat Reduced Water Activity

2018 ◽  
Vol 84 (8) ◽  
pp. e02742-17 ◽  
Author(s):  
Shuxiang Liu ◽  
Juming Tang ◽  
Ravi Kiran Tadapaneni ◽  
Ren Yang ◽  
Mei-Jun Zhu
Keyword(s):  
Relative Humidity ◽  
Thermal Resistance ◽  
Silicon Dioxide ◽  
Linear Relationship ◽  
Water Activity ◽  
Enterococcus Faecium ◽  
Content Type ◽  
Low Moisture Foods ◽  
Log Linear ◽  
Insight Into

ABSTRACTSalmonellaspp. exhibit prolonged survivability and high tolerance to heat in low-moisture foods. The reported thermal resistance parameters ofSalmonellaspp. in low-moisture foods appear to be unpredictable due to various unknown factors. We report here that temperature-dependent water activity (aw, treatment temperature) plays an important role in the sharply increased thermal resistance ofSalmonella entericaserovar Enteritidis PT 30 and its potential surrogateEnterococcus faeciumNRRL B-2354. In our study, silicon dioxide granules, as carriers, were separately inoculated with these two microorganisms and were heated at 80°C with controlled relative humidity between 18 and 72% (resulting in corresponding aw,80°Cvalues for bacteria between 0.18 and 0.72) in custom-designed test cells. The inactivation kinetics of both microorganisms fitted a log-linear model (R2, 0.83 to 0.97). Reductions in the aw,80°Cvalues of bacterial cells exponentially increased theD80°C(the time needed to achieve a 1-log reduction in a bacterial population at 80°C) values forS. Enteritidis andE. faeciumon silicon dioxide. The log-linear relationship between theD80°Cvalues for each strain in silicon dioxide and its aw,80°Cvalues was also verified for organic wheat flour.E. faeciumshowed consistently higherD80°Cvalues thanS. Enteritidis over the aw,80°Crange tested. The estimated zaw(the change in aw,80°Cneeded to changeD80°Cby 1 log) values ofS. Enteritidis andE. faeciumwere 0.31 and 0.28, respectively. This study provides insight into the interpretation ofSalmonellathermal resistance that could guide the development and validation of thermal processing of low-moisture foods.IMPORTANCEIn this paper, we established that the thermal resistance of the pathogenS. Enteritidis and its surrogateEnterococcus faecium, as reflected byDvalues at 80°C, increases sharply with decreasing relative humidity in the environment. The log-linear relationship between theD80°Cvalues of each strain in silicon dioxide and its aw,80°Cvalues was also verified for organic wheat flour. The results provide new quantitative insight into the way in which the thermal resistance of microorganisms changes in low-moisture systems, and they should aid in the development of effective thermal treatment strategies for pathogen control in low-moisture foods.

Influence of low water activity on the thermal resistance of Salmonella Enteritidis PT30 and Enterococcus faecium as its surrogate in egg powders

2020 ◽  
pp. 108201322093787
Author(s):  
Marco E Pérez-Reyes ◽  
Xu Jie ◽  
Mei-Jun Zhu ◽  
Juming Tang ◽  
Gustavo V Barbosa-Cánovas
Keyword(s):  
Thermal Resistance ◽  
Linear Relationship ◽  
Water Activity ◽  
Enterococcus Faecium ◽  
Salmonella Enteritidis ◽  
Thermal Treatments ◽  
Thermal Death ◽  
Industrial Food Production ◽  
Log Linear ◽  
The Impact

Egg powders are increasingly popular ingredients, due to their functionality and compactness, in industrial food production and preparation at homes. However, there is a lack of studies that evaluate the thermal resistance of Salmonella Enteritidis PT30 and its potential surrogate Enterococcus faecium NRRL B-2354 in egg powders. This study examined the log-linear relationship between the thermal resistance of Salmonella Enteritidis (D-value) and the water activity (aw) of egg powders. The changes of aw in the egg powders with temperature were measured using a Vapor Sorption Analyzer and a high-temperature cell. The D80 ℃-value of S. Enteritidis PT30 and E. faecium inoculated in the egg powders preconditioned to three aw levels (0.3, 0.45, and 0.6) at 20 ℃ were determined using aluminum thermal death test cells. The aw values increased (P < 0.05) in all three egg powders when the temperature of the samples was raised from room temperature to 80 ℃. The D80 ℃-values ranged from 5.3 ± 0.1 to 25.9 ± 0.2 min for S. Enteritidis while 10.4 ± 0.4 to 43.8 ± 0.4 for E. faecium in samples of the three different aw levels. S. Enteritidis PT30 showed a log-linear relationship between D80 ℃-values and aw80 ℃ for the egg powders. This study contributes to our understanding of the impact of aw on the development of thermal treatments for low-moisture foods.

scholarly journals Optimization of cellulose nanocrystal length and surface charge density through phosphoric acid hydrolysis

2017 ◽  
Vol 376 (2112) ◽  
pp. 20170041 ◽  
Author(s):  
Oriana M. Vanderfleet ◽  
Daniel A. Osorio ◽  
Emily D. Cranston
Keyword(s):  
Thermal Stability ◽  
Sulfuric Acid ◽  
Phosphoric Acid ◽  
Charge Density ◽  
Acid Hydrolysis ◽  
Acid Concentration ◽  
Large Range ◽  
Phosphate Content ◽  
Hydrolysis Temperature ◽  
Phosphoric Acid Hydrolysis

Cellulose nanocrystals (CNCs) are emerging nanomaterials with a large range of potential applications. CNCs are typically produced through acid hydrolysis with sulfuric acid; however, phosphoric acid has the advantage of generating CNCs with higher thermal stability. This paper presents a design of experiments approach to optimize the hydrolysis of CNCs from cotton with phosphoric acid. Hydrolysis time, temperature and acid concentration were varied across nine experiments and a linear least-squares regression analysis was applied to understand the effects of these parameters on CNC properties. In all but one case, rod-shaped nanoparticles with a high degree of crystallinity and thermal stability were produced. A statistical model was generated to predict CNC length, and trends in phosphate content and zeta potential were elucidated. The CNC length could be tuned over a relatively large range (238–475 nm) and the polydispersity could be narrowed most effectively by increasing the hydrolysis temperature and acid concentration. The CNC phosphate content was most affected by hydrolysis temperature and time; however, the charge density and colloidal stability were considered low compared with sulfuric acid hydrolysed CNCs. This study provides insight into weak acid hydrolysis and proposes ‘design rules’ for CNCs with improved size uniformity and charge density. This article is part of a discussion meeting issue ‘New horizons for cellulose nanotechnology’.

Activity coefficient effects in spectral and solubility studies of molecular complex equilibriums

1972 ◽  
Vol 94 (19) ◽  
pp. 6861-6862 ◽  
Author(s):  
Sherril D. Christian ◽  
Jerry D. Childs ◽  
Edwin H. Lane
Keyword(s):  
Activity Coefficient ◽  
Molecular Complex ◽  
Solubility Studies
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