Ice Crystal Growth in Sucrose Solutions Containing Kappa- and Iota-Carrageenans

Measurements of ice recrystallization inhibition (IRI) and thermal hysteresis (TH) activities of kappa (κ)- and iota (ι)-carrageenans were carried out to examine whether they can be novel cryoprotectants or not. IRI measurements indicate that both carrageenans reduce recrystallization in sucrose solution, but that the IRI activity of κ-carregeenan is higher than that of ι-carrageenan. TH measurements indicate that κ- and ι-carrageenans do not exhibit TH activity. TH activity measurements of antifreeze glycoprotein (AFGP) in the presence of κ-carregeenan demonstrate that this carregeenan neither influences the TH activity of AFGP nor the shape of the ice crystals. The round ice crystal shape transformed into an angular and elongated shape in the presence of both carregeenans.     

Thermodynamic Models and Central Composite Design for Calcium Sulfate Dihydrate Solubility

The solubility of calcium sulfate dihydrate (gypsum) was measured in HCl solutions in the presence of Cr³⁺ and Fe³⁺ ions at various temperatures. The results indicate that the solubility of gypsum is fairly dependent on the concentrations of HCl and impurities, i.e., Cr³⁺ and Fe³⁺ ions. The experimental data were analyzed by applying the Buchowski-Kiazczak (λh) model and the modified Apelblat model. Some thermodynamic parameters, such as the standard molar dissolution enthalpy, the standard molar Gibbs energy, and the entropy of solutions, were calculated by Van't Hoff analysis and Gibbs equation. The influences of the concentrations of both HCl and impurities, i.e., Cr³⁺ and Fe³⁺ ions, and temperature on the gypsum solubility were examined by applying the central composite design.     

Multidimensional Population Balance Modeling for Pathological Calcium Pyrophosphate Dihydrate Crystals in the Presence of Amino Acids

A multidimensional population balance model was applied to elaborate the effects of amino acids on the crystallization mechanisms of calcium pyrophosphate dihydrate crystals. Breakage and growth terms defined in the model were expressed in two dimensions depending on the sizes. The exponential hyperbolic function based on the particle sizes was selected for expressing the growth. The model was resolved by using the finite differences method. It was detected that in the non-additive media, the growth along the length-1 is extremely dominant against both the growth along the length-2 and the breakage. However, it was discovered that the amino acids made the crystals more fragile, and the breakage at certain size ranges and certain concentrations of amino acids was the dominant mechanism. In any case, it was proven that both growth and breakage are suppressed considerably in the amino acid-containing media.     

Thermal Hysteresis and Bursting Rate in Sucrose Solutions with Antifreeze Proteins

Antifreeze proteins (AFPs) modify the ice shape and inhibit further growth leading to thermal hysteresis (TH). Numerous studies have been performed with the addtition of AFPs to preserve frozen products but the influence of sucrose on the effects of AFPs has not been investigated as of yet. Therefore, the TH activities of type I antifreeze protein (AFP I) and antifreeze glycoprotein (AFGP) were measured as a function of concentration, type of AFPs, and also sucrose concentration. The results showed that the TH values rose with increase in concentration of AFPs and sucrose concentration. The crystals experienced shape modification and grew in the c-axis direction in the presence of both AFPs. The bursting rate of crystals changed depending on both the concentrations of AFPs and sucrose.