Topic
Water activity
About: Water activity is a research topic. Over the lifetime, 3602 publications have been published within this topic receiving 93140 citations.
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TL;DR: In this article, the diffusion coefficient and relaxation time of water in the membrane and the protonic conductivity of the membrane as functions of membrane water content were measured, and the ratio of water molecules carried across the membrane per proton transported, the electro-osmotic drag coefficient, was determined for a limited number of water contents.
Abstract: Water uptake and transport properties of Nafion[reg sign] 117 membranes at 30 C are reported here. Specifically, the authors have determined the amount of water taken up by membranes immersed in liquid water and by membranes exposed to water vapor of variable water activity. Transport parameters measured are the diffusion coefficient and relaxation time of water in the membrane and the protonic conductivity of the membrane as functions of membrane water content. The ratio of water molecules carried across the membrane per proton transported, the electro-osmotic drag coefficient, also was determined for a limited number of membrane water contents. The drag coefficient is contrasted with the experimentally determined net water transport across an operating PEM fuel cell.
1,412 citations
TL;DR: In this article, a study was conducted using Buchi mini spray dryer B-191 to produce spray-dried watermelon powders using two different maltodextrin concentrations (3% and 5%) as the encapsulating agent and four different inlet temperatures (145°C, 155¼C, 165 ¼C and 175¼°C).
Abstract: A study was conducted using Buchi mini spray dryer B-191 to produce spray-dried watermelon powders using two different maltodextrin concentrations (3% and 5%) as the encapsulating agent and four different inlet temperatures (145 °C, 155 °C, 165 °C and 175 °C). The spray-dried watermelon powders were analysed for moisture content, dissolution, water activity, colour, lycopene and β-carotene. Results demonstrated that as inlet temperature increased, the moisture content and dissolution decreased. However, there were no significant changes in the water activities of the spray-dried powders for all the inlet temperatures investigated. Colormetric analyses showed that the L * , a * , b * , hue and chroma values changed with the inlet temperatures. The results were well correlated to the lycopene and β-carotene contents of the spray-dried powders.
671 citations
TL;DR: In this paper, the water activity of eight salt solutions was determined at three temperatures (25, 30, 45°C) using a pressure transducer-vapor pressure manometer.
Abstract: The water activity (aw) of eight salt solutions was determined at three temperatures (25, 30, 45°C) using a pressure transducer-vapor pressure manometer. The aws of the salts showed a decrease with increasing temperature, which was explained with the help of a thermodynamic equation. This is opposite to the increase in aw with increase in temperature for foods. Moisture sorption data for fish flour and cornmeal were obtained at 25–65°C. The Guggenheim-Anderson-deBoer model was evaluated and shown to be comparable to the Brunauer-Emmett-Teller model for prediction of the monolayer. Product was equilibrated at different aws at 25°C then subsequently shifted to 30°C and 45°C in a sealed chamber. The resultant a, change, measured on the Kaymont-Rotronics, was predictable from the isotherm at each temperature using the Clausius Clapeyron relationship.
547 citations
TL;DR: CO( 2) adsorption-desorption cycles and the corresponding mechanisms over amine supported CO(2) adsorbent (TRI-PE-MCM-41) under dry conditions and in the presence of moisture are studied.
Abstract: CO2 adsorption−desorption cycles and the corresponding mechanisms over amine supported CO2 adsorbent (TRI-PE-MCM-41) under dry conditions and in the presence of moisture (20 °C as dew point).
522 citations