Beyond Tg: optical luminescence measurements of molecular mobility in amorphous solid foods

Ludescher, Richard D.; Shah, Nikhil R.; McCaul, Colin P.; Simon, Konrad

doi:10.1016/s0268-005x(01)00050-9

Cited by 41 publications

(19 citation statements)

References 17 publications

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“…These factors directly influence systems' molecular mobility, which is responsible for systems' physical properties. In food systems, molecular mobility, together with food microstructure, is also responsible for other quality attributes, like chemical reactivity and organoleptic characteristics [77]. When a liquid is cooled below the melting temperature, and crystallisation is avoided, a rubbery region or supercooled melt ''state'' is observed.…”

Section: Significant Phenomena In Supercooled Sucrosementioning

confidence: 99%

Sucrose in the Concentrated Solution or the Supercooled “State”: A Review of Caramelisation Reactions and Physical Behaviour

2010

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Sucrose is probably one of the most studied molecules by food scientists, since it plays an important role as an ingredient or preserving agent in many formulations and technological processes. When sucrose is present in a product with a concentration near or greater than the saturation point-i.e. in the supercooled state-it possesses high potentialities for the food industry in areas as different as pastry industry, dairy and frozen desserts or films and coatings production. This paper presents a review on critical issues and research on highly concentrated sucrose solutions-mainly, on sucrose thermal degradation and relaxation behaviour in such solutions. The reviewed works allow identifying several issues with great potential for contributing to significant advances in Food Science and Technology.

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Section: Significant Phenomena In Supercooled Sucrosementioning

confidence: 99%

Sucrose in the Concentrated Solution or the Supercooled “State”: A Review of Caramelisation Reactions and Physical Behaviour

2010

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“…16,17 As degradative reactions are modulated by specific modes of molecular mobility-even below T g -it is our goal to find correlations between mobility and reactivity. 18,19 In order to characterize the complex dynamics in amorphous biomaterials, we have extensively utilized triplet state photophysical probes.…”

Section: Introductionmentioning

confidence: 99%

“…20,21 At this state of minimal perturbation, phosphorescence of Ery B emission is sensitive both to the motions of molecules in its immediate environment 19,20 and to the permeability of oxygen. 22,23 From the excited triplet state, a molecule can return to the ground singlet state either by emission of a photon (phosphorescence) or by one of two non-radiative pathways, matrix-induced deactivation or oxygen quenching.…”

Section: Introductionmentioning

confidence: 99%

“…Matrix-induced quenching, in which the excited triplet state undergoes intersystem crossing to an isoenergetic highly excited vibrational state of the ground singlet state, is facilitated by the motions of nearby molecules in the matrix that dissipate the probe vibrational energy 24,25 ; this rate thus provides a measure of local matrix molecular mobility. 19,26 Oxygen quenching, in which the excited triplet state probe transfers its energy to a ground triplet state diatomic oxygen molecule, provides a measure of oxygen permeability through the matrix. 27,28 An important property of the triplet state is its long lifetime due to the forbidden nature of the triplet to singlet state transition.…”

Section: Introductionmentioning

confidence: 99%

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Photophysical Probes of the Amorphous Solid State of Proteins

et al. 2010

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The properties of amorphous solid proteins influence the texture and stability of low-moisture foods, the shelf-life of pharmaceuticals, and the viability of seeds and spores. We have investigated the relationship between molecular mobility and oxygen permeability in dry food protein films-bovine α-lactalbumin (α-La), bovine β-lactoblobulin (β-Lg), bovine serum albumin (BSA), soy 11S globulin, and porcine gelatin-using phosphorescence from the triplet probe erythrosin B. Measurements of the phosphorescence decay in the absence (nitrogen) and presence (air) of oxygen versus temperature provide estimates of the non-radiative decay rate for matrixinduced quenching (k TS0 ) and oxygen quenching (k Q [O 2 ]) of the triplet state. Since the oxygen quenching constant is the product of the oxygen solubility ([O 2 ]) and a term (k Q ) proportional to the oxygen diffusion coefficient, it is a measure of the oxygen permeability through the films. For all proteins except gelatin, Arrhenius plots of k TS0 reveal a gradual increase of apparent activation energy across a broad temperature range starting at ∼50°C; this suggests that there is a steady increase in the available modes of molecular motion with increasing temperature within the protein matrix. Arrhenius plots for k Q [O 2 ] were linear for all proteins with activation energies ranging from 24 to 29 kJ/mol. The magnitude of the oxygen quenching constants varied in the different proteins; the rates were approximately 10-fold higher in α-La, β-Lg, and BSA than in 11S glycinin and gelatin. Although the rate of oxygen permeability was not directly affected by the increased mobility of the protein matrix, plots of k Q [O 2 ] versus k TS0 were linear over nearly three orders of magnitude in the protein films, suggesting that the matrix mobility plays a specific role in modulating oxygen permeability. This effect may reflect differences in matrix-free volume that directly influence both mobility and oxygen solubility.

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“…6 The stability and properties of amorphous biomaterials are modulated by specific physical processes and chemical reactions that are associated with the molecular mobility of amorphous solids. 7 Measurements of mobility of amorphous sucrose are thus of fundamental interest as it relates to questions of stabilization in the biological materials as well as degradation phenomena in amorphous foods. A number of techniques have been applied in characterizing the properties and mobility of amorphous materials including NMR and DSC.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Glycerol on Molecular Mobility in Amorphous Sucrose Detected by Phosphorescence of Erythrosin B

You

Ludescher

2007

Food Biophysics

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Luminescence from the triplet probe erythrosin B provides spectroscopic characteristics such as emission energy and lifetime that are sensitive to molecular mobility of the local solvent environment. This study investigated how variation in glycerol content influences the properties of an amorphous sucrose matrix by monitoring phosphorescence of erythrosin B over the temperature range from 5 to 100°C. Emission energy, lifetime, and red-edge excitation data revealed that glycerol affected the mobility of amorphous sucrose matrix primarily through plasticization when the mole ratio of glycerol/sucrose was above 0.27, resulting in a decrease in emission energy (ν p ), lifetime (C) and energy difference (Δν P ) with excitation at the absorption peak and red edge and an increase in the nonradiative, collisional quenching rate k TS0 . At mole ratios ≤0.27 and at temperatures below the matrix T g , glycerol exhibited an "antiplasticization" effect, as indicated by higher values of emission energy, lifetime, and energy difference and lower values of the matrix collisional quenching rate. Changes in the distribution of emission energy (emission bandwidth) and lifetime, and variation in the emission lifetime vs wavelength showed that glycerol reduced the spectral heterogeneity. These data illustrate the complex effect of a hydrogen bonding solute on the mobility of an amorphous, hydrogen bonded sugar matrix.

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Beyond Tg: optical luminescence measurements of molecular mobility in amorphous solid foods

Cited by 41 publications

References 17 publications

Sucrose in the Concentrated Solution or the Supercooled “State”: A Review of Caramelisation Reactions and Physical Behaviour

Sucrose in the Concentrated Solution or the Supercooled “State”: A Review of Caramelisation Reactions and Physical Behaviour

Photophysical Probes of the Amorphous Solid State of Proteins

The Effect of Glycerol on Molecular Mobility in Amorphous Sucrose Detected by Phosphorescence of Erythrosin B

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