The research on the effect of the milk-clotting ferments of different origin on the milk clots formation

Проведены исследования воздействия химозина, смеси химозина-пепсина и пепсина на коагуляционные свойства молока, а также его УФ-концентрата. По результатам эксперимента наилучшая эффективность сычужного свертывания отмечена в пробах с пепсином, однако для более глубокого анализа кинетики гелеобразования целесообразно применение реологических методов. We conducted the research on the effect of chymozin, mixtures of chymosin-pepsin and pepsin on the coagulation properties of milk, as well as its UV concentrate. According to the results of our experiment, samples with pepsin show the best efficiency of rennet clotting. However, it is advisable to use rheological methods to conduct a more detailed analysis of the kinetics of gelation.

Gelation of Poly(Vinylidene Fluoride) Solutions in Native and Organically Modified Silica Nanopores

The purpose of this study is to highlight the surface and size effects of the nanopores on the thermodynamics and kinetics of gelation. The effects have been probed by applying differential scanning calorimetry to poly(vinylidene fluoride) solutions in tetraethylene glycol dimethyl ether (tetraglyme) and γ-butyrolactone. Nanoconfinement has been accomplished by introducing gels into native and organically modified silica nanopores (4–30 nm). Nanoconfinement has produced two major effects. First, the heat of gelation has decreased three to four times compared to that for the bulk systems. Second, the temperature of gelation has increased by ~40 °C (tetraglyme based systems) and ~70 °C (γ-butyrolactone based systems), the increase being stronger in native nanopores. The effects are discussed in terms of acceleration of gelation due to heterogeneous nucleation at the confining surface, and retardation of gelation due to constricted polymer chain mobility in the middle of the pore volume. Calorimetric data have been subjected to isoconversional kinetics analysis. The obtained temperature dependencies of the activation energies of gelation have been interpreted in the frameworks of the nucleation model of Turnbull and Fisher. The results suggest that nanoconfinement leads to a lowering of both the free energy of nucleation and activation energy of diffusion.

Transparent Monolithic Metal Ion Containing Nanophase Aerogels

ABSTRACTThe formation of monolithic and transparent transition metal containing aerogels has been achieved through cooperative interactions of high molecular weight functionalized carbohydrates and silica precursors, which strongly influence the kinetics of gelation. After initial gelation, subsequent modification of the ligating character of the system, coordination of the group VIII metal ions, and supercritical extraction afford the aerogels. The structures at the nanophase level have been probed by photon and electron transmission and neutron scattering techniques to help elucidate the basis for structural integrity together with the small entity sizes that permit transparency in the visible range. They also help with understanding the chemical reactivities of the metal-containing sites in these very high surface area materials. These results are discussed in connection with new reaction studies.