Sucrose solution freezing studied by magnetic resonance imaging.

Area of Science:

• Food science and technology
• Biophysics
• Materials science

Background:

• Sucrose solutions are widely used in food and pharmaceutical applications.
• Understanding their phase transitions, particularly glass transition, is crucial for product stability and quality.
• Traditional methods like calorimetry face limitations at specific concentrations and temperatures.

Purpose of the Study:

• To investigate the feasibility of using magnetic resonance imaging (MRI) to monitor ice formation and determine the glass transition temperature (Tg) of frozen sucrose solutions.
• To develop and validate an experimental setup for precise temperature control during MRI measurements.
• To assess MRI's capability in characterizing spatial ice distribution within the frozen matrix.

Main Methods:

• Utilized an original experimental setup with oil as a cooling fluid for accurate temperature control from 0 to -50°C.
• Employed Nuclear Magnetic Resonance (NMR) signal intensity monitoring of sampled volumes during cooling.
• Applied high-resolution MRI with isotropic resolution (78x78x78 µm³) to visualize spatial ice distribution.

Main Results:

• Observed a distinct peak in NMR signal intensity preceding signal loss, indicative of a phase transition.
• Successfully monitored ice formation and phase transitions in a 20% w/v sucrose solution.
• Demonstrated high-resolution MRI's ability to map the spatial distribution of ice within the frozen sample.

Conclusions:

• MRI is a novel and effective technique for determining the glass transition temperature of frozen sucrose solutions.
• This method is particularly valuable in concentration ranges where conventional calorimetric measurements are not feasible.
• The developed MRI approach offers precise insights into ice formation dynamics and spatial heterogeneity in frozen systems.