The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform
Masahiro Yoshizawa - One of the best experts on this subject based on the ideXlab platform.
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ionic liquids by proton transfer vapor pressure conductivity and the relevance of δpka from aqueous solutions
Journal of the American Chemical Society, 2003Co-Authors: Masahiro Yoshizawa, Wu Xu, Charles AngellAbstract:We describe the behavior of the conductivity, viscosity, and vapor pressure of various binary liquid systems in which proton transfer occurs between neat Bronsted acids and bases to form salts with melting Points below ambient. Such liquids form an important subgroup of the ionic liquid (IL) class of reaction media and electrolytes on which so much attention is currently being focused. Such “protic ionic liquids” exhibit a wide range of thermal stabilities. We find a simple relation between the limit set by Boiling, when the total vapor pressure reaches one atm, and the difference in pKa value for the acid and base determined in dilute aqueous solutions. For ΔpKa values above 10, the Boiling Point Elevation becomes so high (>300 °C) that preemptive decomposition prevents its measurement. The completeness of proton transfer in such cases is suggested by the molten salt-like values of the Walden product, which is used to distinguish good from poor ionic liquids. For the good ionic liquids, the hydrogen bond...
Richard W. Hartel - One of the best experts on this subject based on the ideXlab platform.
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Non-equilibrium States in Confectionery
Non-Equilibrium States and Glass Transitions in Foods, 2016Co-Authors: Richard W. Hartel, Christine M NowakowskiAbstract:Many confections are governed by non-equilibrium states and glass transitions, both during manufacture and throughout shelf life. In general, sugar confections contain sucrose and glucose syrup as the main sweeteners, along with a variety of additives that distinguish each class of confections. The sugar syrup is boiled to remove excess water, and the final cook temperature determines the final water content through the Boiling Point Elevation curve. During cooling, other ingredients may be added (e.g., colors, flavors, and acids) and/or other operations performed (e.g., aeration), again to distinguish the class of confections. Upon cooling to ambient temperatures, these confections generally are categorized as supersaturated solutions, in either the amorphous or glassy state. As such, they are unstable and prone to changes during storage, which may include moisture uptake or loss, crystallization, and flavor loss. This chapter will provide an overview of manufacture and formation of these products before delving into stability during storage and the mechanisms of collapse.
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Moisture and Shelf Life in Sugar Confections
Critical Reviews in Food Science and Nutrition, 2010Co-Authors: Roja Ergun, R. Lietha, Richard W. HartelAbstract:From hardening of marshmallow to graining of hard candies, moisture plays a critical role in determining the quality and shelf life of sugar-based confections. Water is important during the manufacturing of confections, is an important factor in governing texture, and is often the limiting parameter during storage that controls shelf life. Thus, an understanding of water relations in confections is critical to controlling quality. Water content, which is controlled during candy manufacturing through an understanding of Boiling Point Elevation, is one of the most important parameters that governs the texture of candies. For example, the texture of caramel progresses from soft and runny to hard and brittle as the moisture content decreases. However, knowledge of water content by itself is insufficient to controlling stability and shelf life. Understanding water activity, or the ratio of vapor pressures, is necessary to control shelf life. A difference in water activity, either between candy and air or betwe...
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Moisture and shelf life in sugar confections
Critical Reviews in Food Science and Nutrition, 2010Co-Authors: Recai Ergun, R. Lietha, Richard W. HartelAbstract:From hardening of marshmallow to graining of hard candies, moisture plays a critical role in determining the quality and shelf life of sugar-based confections. Water is important during the manufacturing of confections, is an important factor in governing texture, and is often the limiting parameter during storage that controls shelf life. Thus, an understanding of water relations in confections is critical to controlling quality. Water content, which is controlled during candy manufacturing through an understanding of Boiling Point Elevation, is one of the most important parameters that governs the texture of candies. For example, the texture of caramel progresses from soft and runny to hard and brittle as the moisture content decreases. However, knowledge of water content by itself is insufficient to controlling stability and shelf life. Understanding water activity, or the ratio of vapor pressures, is necessary to control shelf life. A difference in water activity, either between candy and air or between two domains within the candy, is the driving force for moisture migration in confections. When the difference in water activity is large, moisture migration is rapid, although the rate of moisture migration depends on the nature of resistances to water diffusion. Barrier packaging films protect the candy from air whereas edible films inhibit moisture migration between different moisture domains within a confection. More recently, the concept of glass transition, or the polymer science approach, has supplemented water activity as a critical parameter related to candy stability. Confections with low moisture content, such as hard candy, cotton candy, and some caramels and toffees, may contain sugars in the amorphous or glassy state. As long as these products remain below their glass transition temperature, they remain stable for very long times. However, certain glassy sugars tend to be hygroscopic, rapidly picking up moisture from the air, which causes significant changes that lead to the end of shelf life. These products need to be protected from moisture uptake during storage. This review summarizes the concepts of water content, water activity, and glass transition and documents their importance to quality and shelf life of confections.
Charles Angell - One of the best experts on this subject based on the ideXlab platform.
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ionic liquids by proton transfer vapor pressure conductivity and the relevance of δpka from aqueous solutions
Journal of the American Chemical Society, 2003Co-Authors: Masahiro Yoshizawa, Wu Xu, Charles AngellAbstract:We describe the behavior of the conductivity, viscosity, and vapor pressure of various binary liquid systems in which proton transfer occurs between neat Bronsted acids and bases to form salts with melting Points below ambient. Such liquids form an important subgroup of the ionic liquid (IL) class of reaction media and electrolytes on which so much attention is currently being focused. Such “protic ionic liquids” exhibit a wide range of thermal stabilities. We find a simple relation between the limit set by Boiling, when the total vapor pressure reaches one atm, and the difference in pKa value for the acid and base determined in dilute aqueous solutions. For ΔpKa values above 10, the Boiling Point Elevation becomes so high (>300 °C) that preemptive decomposition prevents its measurement. The completeness of proton transfer in such cases is suggested by the molten salt-like values of the Walden product, which is used to distinguish good from poor ionic liquids. For the good ionic liquids, the hydrogen bond...
Xidong Wang - One of the best experts on this subject based on the ideXlab platform.
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calculations of freezing Point depression Boiling Point Elevation vapor pressure and enthalpies of vaporization of electrolyte solutions by a modified three characteristic parameter correlation model
Journal of Solution Chemistry, 2009Co-Authors: Xinlei Ge, Xidong WangAbstract:A method was proposed for calculating the thermodynamic properties, freezing Point depression, Boiling Point Elevation, vapor pressure and enthalpy of vaporization for single solute electrolyte solutions, including aqueous and nonaqueous solutions, based on a modified three-characteristic-parameter correlation model. When compared with the corresponding literature values, the calculated results show that this method gives a very good approximation, especially for 1-1 electrolytes. Although the method is not very suitable for some solutions with very high ionic strength, it is still a very useful technique when experimental data is scarce.
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estimation of freezing Point depression Boiling Point Elevation and vaporization enthalpies of electrolyte solutions
Industrial & Engineering Chemistry Research, 2009Co-Authors: Xinlei Ge, Xidong WangAbstract:A novel approach is presented in this work for predicting the values of freezing Point depression and Boiling Point Elevation for electrolyte solutions at different concentrations on the basis of the Pitzer theories. This method treats the enthalpy change of the solution between the normal freezing Point or Boiling Point and the real ones to be linear temperature dependence. Compared with the literature values, this method performs very well; also, the temperature-dependent parameters of some salts are incorporated to investigate temperature effects of this method. Furthermore, a method based on the Clausius−Clapeyron equation is derived for estimation of the enthalpy of vaporization of very high concentration solutions at different temperatures, and the predicted results are highly positive.
Bin Wang - One of the best experts on this subject based on the ideXlab platform.
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thermal analysis for the evaporation concentrating process with high Boiling Point Elevation based exhaust waste heat recovery
Desalination, 2018Co-Authors: Bin WangAbstract:Abstract In order to reduce energy consumption of the solution evaporation concentrating process with high Boiling Point Elevation (BPE), a novel cogeneration system is proposed to integrate the solution evaporation concentrating and power generation processes using the exhaust waste heat as heat source. Through compared with the conventional three-effect and mechanical vapor recompression evaporation processes, influences from the key operation parameters, including the evaporation temperature and BPE of the solution on overall thermal performance of the proposed system have been investigated. The results showed the overall thermal performance of the three schemes became worse with the rise of the BPE, but the proposed cogeneration system showed prominent thermal performance when dealing solutions with high BPE compared to those of the conventional three-effect and MVR evaporating processes. Moreover, through harmonizing the vacuum evaporation concentrating process and net power output, the optimal evaporating temperatures to achieve the maximal energy saving potential are obtained under different BPE working conditions for the proposed cogeneration system.
