Determination and correlation of the water activity of propylene glycol solutions

1994 ◽  
Vol 27 (1) ◽  
pp. 65-67 ◽  
Author(s):  
Stella M. Alzamora ◽  
Jorge Chirife ◽  
Lía N. Gerschenson
Keyword(s):  
Propylene Glycol ◽  
Water Activity

Combined Water Activity and Solute Effects on Growth and Survival of Listeria monocytogenes Scott A

1992 ◽  
Vol 55 (6) ◽  
pp. 414-418 ◽  
Author(s):  
A. J. MILLER
Keyword(s):  
Listeria Monocytogenes ◽  
Propylene Glycol ◽  
Water Activity ◽  
Growth And Survival

Water activity and solute effects were determined on the growth and survival of Listeria monocytogenes Scott A in bacteriological media. Media were adjusted to water activity (aw) levels of 0.99-0.80 with NaCl, glycerol (GLY), or propylene glycol (PG). Minimum aw levels for growth occurred at 0.90, 0.92, and 0.97 for GLY, NaCl, and PG, respectively. Survival was related to the aw level, as well as the solute employed. Cells survived the longest in GLY and died earliest in PG; NaCl was intermediate. These results provide quantitative isothermal criteria for estimating the aw level necessary to prevent growth of L. monocytogenes in food.

Molecular dynamics of poly(propylene) glycol in nanometer confinements

2000 ◽  
Vol 10 (PR7) ◽  
pp. Pr7-271-Pr7-274 ◽  
Author(s):  
A. Schönhals ◽  
H. Goering ◽  
K.-W. Brzezinka ◽  
Ch. Schick
Keyword(s):  
Molecular Dynamics ◽  
Propylene Glycol ◽  
Poly Propylene

Hydrogenolysis of glucose and fructose in glycol solutions over CuO-MgO-ZrO2 catalyst

2020 ◽  
pp. 48-55
Author(s):  
M.E. Sharanda ◽  
◽  
E.A. Bondarenko ◽  
Keyword(s):  
Ethylene Glycol ◽  
Propylene Glycol ◽  
Flow Reactor ◽  
General Trend ◽  
Raw Materials ◽  
Reaction Products ◽  
Renewable Raw Materials ◽  
High Partial Pressure ◽  
Zro2 Catalyst ◽  
Phase Process

Ethylene glycol and propylene glycol are important representatives of polyols. On an industrial scale, they are obtained from petrochemical raw materials. Within a decade, significant efforts were made for the producing of polyols from biologically renewable raw materials - carbohydrates. The general trend for carbohydrate hydrogenolysis includes application of liquid-phase process with the use of modified metal-oxide catalysts, at 120-120 ° C and pressure of 3MPa or above. So high pressure is used for the reason to increase hydrogen solubility, and also due to the high partial pressure of low boiling solvents. We supposed that usage of high boiling solvents could allow hydrogenolysis to be performed at the lower pressure. Ethylene glycol and propylene glycol are of particular interest as such kind of solvent since they are both the main products of glucose hydrogenolysis. In this work, the process of hydrogenolysis of glucose and fructose over Cu / MgO-ZrO2 catalyst have been studied at temperature range of 160-200 °C and a pressure of 0.1-0.3 MPa in a flow reactor. The solvents were simultaneously the target products of the reaction - ethylene glycol and / or propylene glycol. Gas chromatography and 13C NMR were used for the reaction products identification. It was found that the solubility of glucose in propylene glycol is 21 % by weight, and in ethylene glycol 62% by weight. It was pointed out that the process of hydrogenolysis can take place at a pressure close to atmospheric. Under these conditions, the conversion of hexoses reaches 96-100 %. The reaction products are preferably propylene glycol and ethylene glycol. The total selectivity for C3-2 polyols is 90-94 %, that is higher than in the hydrogenolysis of glucose in aqueous solution.

Obtaining and Characterisation of Starch-Based Edible Films Incorporating Honey, Propolis and Bee Bread

2019 ◽  
Vol 23 (2) ◽  
pp. 193-198
Author(s):  
Monica Mironescu ◽  
Laura Fratila ◽  
Alexandru Hupert ◽  
Ion Dan Mironescu
Keyword(s):  
Water Activity ◽  
Mechanical Characteristics ◽  
Edible Films ◽  
Ash Content ◽  
Colour Intensity ◽  
Sensorial Analysis ◽  
Physical Chemical ◽  
Control Film ◽  
Bee Bread

Abstract This research investigates the physical-chemical, sensorial and mechanical characteristics of starch-based edible films incorporating three types of bee hive products: honey, propolis and bee bread, in concentrations varying from 1% to 3%, reported to starch. The results indicates an increasing of films moisture, water activity, ash content and acidity, in the order: honey<propolis<bee bread, all values increasing with the increasing of hive products percentage into the control film; aw is remaining at very low values, under 0.4. Sensorial analysis indicated honey as the better suited for improving taste and flavour and bee bread for increasing colour intensity of the films; the sensorial characteristics are maintained during 30 days of films storage, in all cases. Compared with the control starch-based film (which is elastic, brittle and hard), the films containing 2% bee hive products are elasto-plastic and more resistant to penetration, the resistance increasing in the order: bee bread<propolis<honey.

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