The calorimetry of kappa carrageenan using differential scanning calorimetry and calorimetry at constant temperature is presented. Both sets of experimental results confirmed the formation of a helical dimer in the absence of gel formation. When gel is formed, the formation of a helical dimer is the major effect, the contribution of gelation represents only 20% of the enthalpy recorded.
Authors:Nalinda Almeida, Stanley Hirschi, Anja Mueller, and Leela Rakesh
Viscoelastic properties of κ-carrageenan in saline solution at various concentrations and pH were investigated by dynamic
rheological techniques, viscosity, elasticity measurements, and IR spectrometry. The viscosity and elasticity at low concentrations
of κ-carrageenan do not depend on pH, confirming that κ-carrageenan is in a disordered conformation. At 0.7% κ-carrageenan,
the disordered confirmation transforms into an ordered helical confirmation with the possibility of weak-type gel formation.
The transformation is also confirmed by dynamic measurements of loss and storage moduli. Furthermore, at this concentration,
the viscosity and elasticity are highly dependent on pH. At higher concentrations of NaCl (0.5 M) at some pHs, we observed
that storage moduli is greater than loss moduli for the entire frequency region. Hence, there is a possibility of structure
transformation from weak-type gel to a somewhat intermediate gel. The lowest viscosity and elasticity were obtained at extreme
pH, confirming that there are structural changes occurring at these pHs due to hydrolysis. This is confirmed by IR data.
during the period required for the accumulation of protein-rich ascitic fluid. In the present work, four macromolecules were selected for the induction of inflammatory ascites: two complex carbohydrates (zymosan and γ-carrageenan), a polycation
Authors:M. Sorrenti, L. Catenacci, M. Bonferoni, G. Sandri, C. Caramella, and G. Bettinetti
Interactions between diltiazem hydrochloride (DTZ), an orally active calcium antagonist used in the treatment of angina and
hypertension, and lambda carrageenan (λCRG), which has been successfully used in matrix formulations to obtain constant and pH-independent release of basic drugs,
were investigated in solid state using differential scanning calorimetry (DSC) and thermogravimetric analysis (TG). The effect
of particle size on thermal behaviour of the drug and the polymer was assessed, and the result used to select the most suitable
granulometric fractions for the study. Physical mixtures ranging in composition from 3:1 to 0.6:1 (by weight) drug-to-polymer
ratios were analyzed as such and after kneading. A stoichiometric ratio of interaction of 1.6:1 (w/w) DTZ:λCRG was found, in agreement with that obtained from dialysis equilibrium studies. All the examined granulometric fractions
(<45 μm, 45–75 μm, 75–105 μm and >105 μm) of the interaction product showed similar thermal behaviour.
Authors:Y. Wakabayashi, K. Ito, H. Li, Y. Ujihira, H. Hashimoto, H. Matsui, A. Chiba, and Y. Jean
Positron annihilation lifetime measurement was applied to study the sol-gel transition of anionic polysaccharide aqueous solutions in terms of free-volume parameters the size, intensity, and size distribution of free volumes of the gelation of K-formk-carrageenan solutions as a function of temperature. Slight variations of free volume size and intensity against temperature were observed near 295 K. The correlation of free-volume data with other physical properties vibrational spectra (IR and Raman), conductivity, SAXS, elastic measurement, differential scanning calorimetry were investigated to understand the mechanism of sol-gel transition of carrageenan.
Initial freezing points Ti of egg samples (melange of egg yolk and white, egg yolk, egg white) and surimi mixed with different mass fractions of . -carrageenan (w = 1O10%), NaCl (w = 1O10%), and mixtures of NaCl and . -carrageenan in mass ratio of 4:1 (w = 1O10%) were determined by use of differential thermal analysis (DTA). Samples of surimi were prepeared in laboratory conditions from Sardina pilchardus. Water content in surimi was 81.50%, in egg yolk 47.65%, in egg white 88.1%, and in melange it was 64.41% before mixing with the added substances. Relations between decrease of the initial freezing point Ti as function of mass fractions w of the added substances were determined by linear regression. Coefficients of determination in range of R 2 = 0.94O0.98 for samples of surimi, and R 2 = 0.92O0.98 for samples of egg were obtained. The largest effect of cryoscopic depression on initial freezing point Ti were exhibited by the samples of surimi with added: a) NaCl in the temperature range from O0.19 to O11.11 °C, b) mixtures of NaCl and . -carrageenan (from O0.19 to O9.08 °C), and c) . -carrageenan (from O0.19 to O0.72 °C). For the samples with pure NaCl the largest decrease of Ti was obtained for: a) egg yolk (from O0.59 to O20.77 °C), b) melange (from O0.59 to O8.74 °C), and c) egg white (from O0.50 to O7.37 °C). The results are compared and discussed with Chang-Tao model for prediction of Ti for meat.
Authors:G. Regdon, A. Kósa, I. Erős, and K. Pintye-Hódi
Differential scanning calorimetry (DSC) was used in the investigation of the behaviour of coating free films. The films were
produced from two film-forming polymers which are chemically different but equally used for producing controlled-release dosage
forms: Eudragit NE 30 D (synthetically produced polymethacrylate copolymer) and LustreClear product (mixture containing natural
and semi-synthetic components: microcrystalline cellulose, hydroxy-ethyl cellulose, carrageenan and polyethylene glycol).
During their comparative analysis the characteristic parameters of the DSC curves obtained with dynamic measurement method
were used and their changes as a function of storage conditions and storage time were observed. It was found that the thermoanalytical
behaviour of the examined methacrylate-based Eudragit NE and cellulose-based LustreClear films was different. The specific
enthalpy change of Eudragit NE fresh films was very little, but it increased considerably during storage. The specific enthalpy
change of LustreClear films was much greater but its value shows only a slight further increase during storage. The results
obtained help to choose the proper temperature for coating and drying.