Viscosities of aqueous solutions of sucrose and sodium chloride of interest in osmotic dehydration processes

Chenlo, F.; Moreira, Ramón; Pereira, Goreti; Ampudia, A

doi:10.1016/s0260-8774(01)00221-7

Cited by 101 publications

(80 citation statements)

References 15 publications

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“…Thus, considering that citric acid is currently cheaper than ascorbic acid, condition 7 (0.75% citric acid) could be indicated as the of both water and sugar was faster. This is probably due to the swelling and plasticization suffered by the cell membrane during osmotic dehydration at higher temperatures, which led to an increase in its permeability (UDDIN; AINSWORTH; IBANOGLU, 2004) and a reduction in the viscosity of the osmotic solution (CHENLO et al, 2002).…”

Section: Osmotic Dehydration Kineticsmentioning

confidence: 99%

Effect of process variables on the osmotic dehydration of star-fruit slices

et al. 2012

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The objective of this work was to study the effect of blanching and the influence of temperature, solution concentration, and the initial fruit:solution ratio on the osmotic dehydration of star-fruit slices. For blanching, different concentrations of citric and ascorbic acids were studied. The samples immersed in 0.75% citric acid presented little variation in color in relation to the fresh star-fruit. Osmotic dehydration was carried out in an incubator with orbital shaking, controlled temperature, and constant shaking at 120 rpm. The influence of process variables was studied in trials defined by a complete 23 central composite design. In general, water loss and solids gain were positively influenced by temperature and by solution concentration. Nevertheless, lower temperatures reduced water loss throughout the osmotic dehydration process. An increase in the amount of dehydrating solution (initial fruit:solution ratio) slightly influenced the evaluated responses. The process carried out at 50 ºC with a solution concentration of 50% resulted in a product with lower solids gain and greater water loss. Under these conditions, blanching minimized the effect of the osmotic treatment on star-fruit browning, and therefore the blanched fruits showed little variation in color in relation to the fresh fruit.

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Section: Osmotic Dehydration Kineticsmentioning

confidence: 99%

Effect of process variables on the osmotic dehydration of star-fruit slices

et al. 2012

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“…For each ternary mixture of sucrose, sodium chloride, and water, we use the parameterization of Chenlo (19) to calculate the dependence of the dynamic viscosity (Pa s) on water activity, providing the best currently available method for estimating the viscosity for this system. The Aerosol Diameter Dependent Equilibrium Model (ADDEM) (20) is used to estimate solute molality and solution density as a function of RH.…”

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confidence: 99%

“…Similarly, at viscosities above 10 4 Pa s, the timescale measurements should be interpreted with caution, with likely errors incurred in both the viscosity and time constant estimates. Given that the high viscosity measurements require a considerable extrapolation of the viscosity data, it is likely that the viscosity estimates could be in error by orders of magnitude (19). In addition, fitting a single exponential decay to the size response represents a simplification of the actual process, particularly under very dry/ high viscosity conditions.…”

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confidence: 99%

Comparing the mechanism of water condensation and evaporation in glassy aerosol

Bones

Reid

Lienhard

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

190

255

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Atmospheric models generally assume that aerosol particles are in equilibrium with the surrounding gas phase. However, recent observations that secondary organic aerosols can exist in a glassy state have highlighted the need to more fully understand the kinetic limitations that may control water partitioning in ambient particles. Here, we explore the influence of slow water diffusion in the condensed aerosol phase on the rates of both condensation and evaporation, demonstrating that significant inhibition in mass transfer occurs for ultraviscous aerosol, not just for glassy aerosol. Using coarse mode (3-4 um radius) ternary sucrose/sodium chloride/aqueous droplets as a proxy for multicomponent ambient aerosol, we demonstrate that the timescale for particle equilibration correlates with bulk viscosity and can be ≫10 3 s. Extrapolation of these timescales to particle sizes in the accumulation mode (e.g., approximately 100 nm) by applying the Stokes-Einstein equation suggests that the kinetic limitations imposed on mass transfer of water by slow bulk phase diffusion must be more fully investigated for atmospheric aerosol. Measurements have been made on particles covering a range in dynamic viscosity from <0.1 to >10 13 Pa s. We also retrieve the radial inhomogeneities apparent in particle composition during condensation and evaporation and contrast the dynamics of slow dissolution of a viscous core into a labile shell during condensation with the slow percolation of water during evaporation through a more homogeneous viscous particle bulk.water uptake | whispering gallery modes | Raman spectroscopy | optical tweezers | viscous aerosol A tmospheric aerosol particles are typically complex mixtures of organic and inorganic species with correspondingly complex equilibria and temporal responses to changes in humidity. Secondary organic aerosols (SOA) continue to receive a great deal of attention due to their impact on radiative forcing, mainly through the indirect effect (1). Ambient aerosol typically contains a significant organic fraction, arising from the oxidation of volatile organic compounds (2). SOA has been largely thought of as existing as a liquid phase, or as a combination of a solid phase within a liquid droplet, but the reality is likely to be far more nuanced. Recently, Virtanen et al. demonstrated that ambient SOA particles can have similar mechanical properties to crystalline ðNH 4 Þ 2 SO 4 particles at 10-20% RH but exist as amorphous glasses to low relative humidity (RH) rather than forming crystalline phases (3). This picture is consistent with the conclusions of Mikhailov et al. (4) and Zobrist et al. (5), who suggested that the existence of glassy states may have profound consequences for the properties of atmospheric aerosol particles, particularly at low temperatures.The term glassy refers to an amorphous, highly viscous state with a dynamic viscosity (η) of greater than 1 × 10 12 Pa s and the mechanical properties of a solid (6). In thermodynamic terms, a glass is in a nonergodic metastable state...

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“…Além disso, a viscosidade afeta também a taxa de transferência de massa do processo. Quando o meio osmótico é altamente viscoso, a transferência de massa pode ser dificultada e, desse modo, a consideração de que a resistência externa à transferência de massa é desprezível (presente na maioria dos modelos que descrevem a desidratação osmótica) nem sempre é vá-lida [7]. Normalmente, costuma-se conduzir o processo de desidratação osmótica sob agitação, visando-se minimizar os efeitos desta resistência externa.…”

Section: -Introduçãounclassified

Estudo da desidratação osmótica de tomate em soluções ternárias pela metodologia de superfície de resposta

Tonon¹,

Baroni²,

Hubinger³

2006

Ciênc. Tecnol. Aliment.

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rEsumoO objetivo deste trabalho foi estudar a influência da temperatura (20 -40 °C), da composição da solução (0% NaCl/65% sacarose -10% NaCl/55% sacarose) e do nível de agitação (0 -1000 rpm), na desidratação osmótica de metades de tomate. O processo foi realizado em um tanque encamisado conectado a um banho termostático, sendo a agitação da solução osmótica promovida por um agitador mecânico e medida por um tacômetro digital. Os resultados foram analisados por metodologia de superfície de resposta, de acordo com um planejamento experimental fatorial 2 3 completo. A perda de água, o ganho de sal e de sacarose e a atividade de água final dos produtos foram influenciados positivamente pela temperatura e pelo aumento do teor de sal na solução. A agitação influenciou somente a perda de água, indicando que, neste caso, a transferência de massa não é governada apenas por um mecanismo interno de difusão. A proximidade do equilíbrio atingida em cada ensaio foi verificada pela relação entre as atividades de água da solução e das amostras. As amostras processadas em soluções com maior quantidade de sal foram as que se apresentaram mais distantes do equilíbrio, após 3 h de processo. palavras-chave: Lycopersicum esculentum, desidratação osmótica, transferência de massa, planejamento experimental, atividade de água. summarY STUDY OF OSMOTIC DEHYDRATION OF TOMATO IN TERNARY SOLUTIONS THROUGH RESPONSE SURFACE METHODOLOGY.The objective of this work was to study the influence of temperature (20 -40 °C), solution composition (0% NaCl/65% sucrose -10% NaCl/55% sucrose) and agitation level (0 -1000 rpm), on the osmotic dehydration of tomato's halves. The process was carried out in a jacketed tank connected to a thermostatic bath, and osmotic solution agitation was promoted by a mechanical stirrer and measured by a digital tachometer. Results were analyzed through response surface methodology, according to a 2 3 factorial experimental design. Water loss, salt and sucrose gain and final water activity of the product were positively influenced by temperature and by increasing salt content on the solution. Agitation influenced only on water loss, indicating that in this case, mass transfer is not governed only by a diffusion internal mechanism. Equilibrium proximity reached in each test was verified through the relationship between solution and samples water activities. The samples processed in solutions with higher salt content seemed to be more distant of equilibrium, after 3 hours of process. Keywords: Lycopersicum esculentum, osmotic dehydration, mass transfer, experimental desing, water activity. -introduçãoO tomate é um dos vegetais mais consumidos no mundo, tanto na forma in natura (em saladas), como na forma industrializada (em molhos, sucos, ketchup ou mesmo seco), sendo o segundo vegetal em área cultivada e o primeiro em volume industrializado. No Brasil, os maiores produtores são os Estados de Goiás, São Paulo, Minas Gerais, Pernambuco e Bahia, responsáveis por 77% da produção anual de tomate [1]. Em 2004, a produção nacion...

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Viscosities of aqueous solutions of sucrose and sodium chloride of interest in osmotic dehydration processes

Cited by 101 publications

References 15 publications

Effect of process variables on the osmotic dehydration of star-fruit slices

Effect of process variables on the osmotic dehydration of star-fruit slices

Comparing the mechanism of water condensation and evaporation in glassy aerosol

Estudo da desidratação osmótica de tomate em soluções ternárias pela metodologia de superfície de resposta

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