Quantitative Phase Analysis of the Hydrothermally Treated System γ-Ca2SiO4-CaO

A multiphase product of hydrothermal reaction in a system γ-Ca₂SiO₄-CaO, at a Ca/Si molar ratio of 2.25 and 200°C, was subjected to quantitative phase analysis by XRD and selective dissolution in a methanolic solution of salicylic acid. The step-wise procedure required by the general method of phase analysis included: (1) determination of the number of phases with overlapping XRD patterns, (2) determination of the individual XRO patterns from diffraction patterns of multiphase samples, and (3) determination of weight fractions for all coexisting crystalline constituents. The derived individual XRD patterns correspond to calciochondrodite, "γ-dicalcium silicate hydrate," and rankinite, a phase not hitherto reported to be formed at 200°C under saturated steam conditions. The method was checked on the model system xonotlitetobermorite-calcite.     

Anthocyanin Degradation in the Presence of Furfural and 5-Hydroxymethylfurfural

The influence of furfural (F) and 5-hydroxymethylfurfural (HMF) on degradation of cyanidin-3-glucoside (CG) was investigated in blackberry juice and in a citrate buffer model solution (pH 3,45) at 24°, 50° and 70°C. Presence of 0.012 M F or HMF accelerated pigment degradation. The acceleration was directly temperature-dependent, more pronounced in fruit juice, and considerably decreased in nitrogen. CG and HMF disappearance – but not the interaction between these compounds – followed the first-order reaction kinetics. The influence of formaldehyde (Fa) acetaldehyde (Aa) and benzaldehyde (Ba) on the stability of CG was investigated in blackberry juice. CG degradation effect of non-furane aldehydes (0.012 M) was Fa < Aa < Ba. CG and cyanidine (C) reactivities were studied by condensation with F and examination of molecular electrone properties (cyanidine, keto-pseudobase, anhydrobase, chalcone). Furfural did not react with CG but it did react with C. Electron charge distribution points to anhydrobase as the tautomeric form of C most reactive to F. Possible mechanisms of C decomposition in presence of F are proposed and discussed.