Modelling of physical ageing in starch using the TNM equation.

Gelatinised wheat starch, freeze dried and equilibrated at different RH, was aged at different temperatures and for different times. The Tool-Narayanaswamy-Moynihan (TNM) model was used to describe the ageing for all samples under all conditions. Three TNM parameters: x, Δh* and A were determined experimentally using, respectively, the peak shift method (x) and the dependency of T'(f) (the limiting value of T(f)) on the cooling rate (Δh* and A).

Modeling of temperature-induced near-infrared and low-field time-domain nuclear magnetic resonance spectral variation: chemometric prediction of limonene and water content in spray-dried delivery systems.

The influence of temperature on near-infrared (NIR) and nuclear magnetic resonance (NMR) spectroscopy complicates the industrial applications of both spectroscopic methods. The focus of this study is to analyze and model the effect of temperature variation on NIR spectra and NMR relaxation data. Different multivariate methods were tested for constructing robust prediction models based on NIR and NMR data acquired at various temperatures.

Solvent-induced lysozyme gels: effects of system composition and temperature on structural and dynamic characteristics.

The gelation process of lysozyme in water/tetramethylurea in the presence of salt was investigated as a function of temperature and system composition by rheology, infrared spectroscopy, and microcalorimetry. Times and temperatures of gelation were determined from the variation of the storage (G') and loss (G'') moduli. It was found that gelation times follow exponential decays with both protein and tetramethylurea (TMU) concentrations and with temperature.

The effect of thermal history on the maillard reaction in a glassy matrix.

To test whether the extent of physical aging affected the reaction rate, Maillard reaction kinetics were studied in glassy model preservation systems subjected to two different thermal histories. The glass transition temperature and physical aging of the matrix were determined using differential scanning calorimetry, and the normalized heat capacities were modeled using the Tool-Narayanaswamy-Moynihan approach. Samples prepared using the different thermal histories initially had different degrees of aging, but these were practically indistinguishable after 10 h under the reaction conditions (65 degrees C); the samples underwent rapid structural relaxation at that temperature.

Physical aging of starch, maltodextrin, and maltose.

The physical aging of low water content, amorphous starch/water, maltodextrin/water, and maltose/water mixtures in the glassy state was examined using mechanical testing and calorimetry. Stress relaxation measurements showed that upon storage of the glassy materials there was a time-dependent increase in both flexural modulus and mechanical relaxation time. The mechanical relaxation time increased with depth of quench below the calorimetric glass transition temperature and with aging time at the quench temperature.

Enthalpy relaxation of bovine serum albumin and implications for its storage in the glassy state.

Two endothermic peaks could be observed for five commercial samples of bovine serum albumin (BSA). The smaller peak observed by differential scanning calorimetry (DSC) corresponded to enthalpy relaxation. This peak was followed on storage of BSA, in its glassy state, after it had been heated above its denaturation temperature.

Comparative study of the retrogradation of intermediate water content waxy maize, wheat, and potato starches.

The retrogradation of extruded starches from three different botanical sources was studied in concentrated conditions (34 +/- 1% water) at 25 degrees C using differential scanning calorimetry (DSC) and isothermal calorimetry, Fourier transform infrared spectroscopy (FTIR), and wide-angle X-ray scattering. Potato starch showed the highest rate of retrogradation (approximately 0.17 h(-1)) followed by waxy maize (approximately 0.

FTIR study of state and phase transitions of low moisture sucrose and lactose.

Mid-infrared spectra of freeze-dried sucrose and lactose systems were acquired over a range of temperatures (30-200 degrees C) and water contents (0-6.3%). Starting from the glassy state, the experimental conditions were selected to cover the main thermal transitions: the glass-rubber transition, the crystallisation and, for some samples, the subsequent melting.

Monitoring chemical and physical changes during thermal flavor generation.

On-line techniques were developed to monitor chemical and physical changes occurring during the heating of skim milk powder (SMP). Atmospheric pressure chemical ionization mass spectrometry (APCIMS) followed the generation and release of volatile compounds from SMP in a packed-bed reactor. Operating conditions were optimized to avoid condensation of high boiling compounds such as maltol, and the system was highly reproducible (CV < 7%).