Dielectric Relaxations of Frozen Wheat Doughs Containing Sucrose, NaCl, Ascorbic Acid and Their Mixtures

Laaksonen, Tommi J.; Roos, Yrjö H.

doi:10.1006/jcrs.2001.0370

Cited by 18 publications

(11 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The present study emphasized changes in dielectric relaxation times and their correlation with the development of stickiness above the glass transition of milk solids (Tables 2 and 3). The dielectric permittivity increased rapidly around the glass transition as the polar groups of molecules exhibited increasing mobility, and a peak above the glass transition occurred in the dielectric loss (Roos, 1995;Ryynänen, 1995;Laaksonen and Roos, 2003). Our previous studies showed that a-relaxations in milk solids occurred above the glass transition associated with powder stickiness (Silalai and Roos, 2010a,b).…”

Section: Dielectric Relaxationsmentioning

confidence: 89%

“…DEA was used to measure changes in dielectric properties from the dielectric constant or permittivity (e 0 ), dielectric loss (e 00 ), and their ratio tan d = (e 00 /e 0 ) as a function of temperature. The e 0 describes an alignment of dipoles (permittivity) and the e 00 (dielectric loss) describes an energy that is required to align dipoles (Talja and Roos, 2001;Laaksonen and Roos, 2003;Silalai and Roos, 2010b). Around 1 g aliquots of each powder were prepared and humidified in vacuum desiccators over saturated salt solutions for 5 days as described by Silalai and Roos (2010b).…”

Section: Dielectric Analysis (Dea)mentioning

confidence: 99%

See 1 more Smart Citation

Coupling of dielectric and mechanical relaxations with glass transition and stickiness of milk solids

Silalai

Roos

2011

Journal of Food Engineering

View full text Add to dashboard Cite

Section: Dielectric Relaxationsmentioning

confidence: 89%

Section: Dielectric Analysis (Dea)mentioning

confidence: 99%

Coupling of dielectric and mechanical relaxations with glass transition and stickiness of milk solids

Silalai

Roos

2011

Journal of Food Engineering

View full text Add to dashboard Cite

“…The behavior of frozen and/or dried biological materials differs from that of fresh materials and research in this behavior is crucial for the possibility to optimize the stability of the treated food. Several studies [5][6][7][8] have been performed on the dynamical behavior of freeze-dried fruits and vegetables. However, most of these studies concentrate on the whole material and very few specifically on the dynamics of its interfacial carbohydrate solution.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of water in strawberry and red onion as studied by dielectric spectroscopy

et al. 2005

View full text Add to dashboard Cite

We have investigated the microscopic dynamics of strawberry and red onion by means of broadband dielectric spectroscopy. In contrast to most of the previous experiments on carbohydrate-rich biological materials, which have mainly considered the more global dynamics of the "biological matrix," we are here focusing on the microscopic dynamics of mainly the associated water. The results for both strawberry and red onion show that the imaginary part of the permittivity contains one conductivity term and a clear dielectric loss peak, which was found to be similar to the strongest relaxation process of water in carbohydrate solutions. The temperature dependence of the relaxation process was analyzed for different water content. The relaxation process slows down, and its temperature dependence becomes more non-Arrhenius, with decreasing water content. The reason for this is most likely that, on average, the water molecules interact more strongly with carbohydrates and other biological materials at low water content, and the dynamical properties of this biological matrix changes substantially with increasing temperature (from an almost rigid matrix where the water is basically unable to perform long-range diffusion due to confinement effects, to a dynamic matrix with no static confinement effects), which also changes (i.e., reduces) the activation energy of the relaxation process with increasing temperature (i.e., causes a non-Arrhenius temperature dependence). This further changes the conductivity from mainly polarization effects at low temperatures, due to hindered ionic motions, to long-range diffusivity at T>250 K . Thus, around this temperature ions in the carbohydrate solution no longer get stuck in confined cavities, since the motion of the biological matrix "opens up" the cavities and the ions are then able to perform long-range migration.

show abstract

“…A mechanical T g can be determined by mechanical spectroscopy (MS) or dynamic mechanical analysis (DMA). Dielectric analysis (DEA) offers another suitable alternative to DSC for determination of glass-transition curves for doughs and frozen doughs [179,180]. These dielectric and mechanical spectroscopic methods are extremely sensitive in observing relaxations as functions of frequency and temperature.…”

Section: Glass-transition Curvementioning

confidence: 99%

“…Such relaxations can involve both sub-T g relaxations, referred as β and γ transitions, and the glass transition itself, which is the main α-denoted relaxation. DEA and DMA have been employed for obtaining complementary information to DSC when analyzing glass transition and crystallization of polyols [54], subzero transitions [179,180] and sub-T g relaxations in different carbohydrate models [54,179,180].…”

Section: Glass-transition Curvementioning

confidence: 99%

State diagrams for improving processing and storage of foods, biological materials, and pharmaceuticals (IUPAC Technical Report)

Buera

Roos

Levine

et al. 2011

Pure and Applied Chemistry

View full text Add to dashboard Cite

Supplemented temperature/composition phase diagrams include the non-equilibrium glass-transition temperature (T g ) curve and equilibrium ice-melting and solubility curves. The inclusion of the non-equilibrium curve allows one to establish relationships with the time coordinate and, thus, with the dynamic behavior of systems, provided that the thermal history of such systems is known.The objective of this report is to contribute to the potential applications of supplemented state diagrams for aqueous glass-formers, in order to describe the influence of water content, nature of vitrifying agents, and temperature on the physico-chemical properties of foods and biological and pharmaceutical products. These data are helpful to develop formulations, processing strategies, or storage procedures in order to optimize the stability of food ingredients and pharmaceutical formulations. Reported experimental data on phase and state transitions for several food and pharmaceutical systems were analyzed. Some methodological aspects and the effect of phase and state transitions on the main potential chemical reactions that can alter those systems during processing and/or storage are discussed.

show abstract

Dielectric Relaxations of Frozen Wheat Doughs Containing Sucrose, NaCl, Ascorbic Acid and Their Mixtures

Cited by 18 publications

References 30 publications

Coupling of dielectric and mechanical relaxations with glass transition and stickiness of milk solids

Coupling of dielectric and mechanical relaxations with glass transition and stickiness of milk solids

Dynamics of water in strawberry and red onion as studied by dielectric spectroscopy

State diagrams for improving processing and storage of foods, biological materials, and pharmaceuticals (IUPAC Technical Report)

Contact Info

Product

Resources

About